Scientific and technological analysis and research on the ink stick unearthed from the tomb of Fanxiaochong of the Northern Song Dynasty in Xi'an, Shaanxi Province

Scientific and technological analysis and research on the ink stick unearthed from the tomb of Fanxiaochong of the Northern Song Dynasty in Xi'an, Shaanxi Province | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Scientific and technological analysis and research on the ink stick unearthed from the tomb of Fanxiaochong of the Northern Song Dynasty in Xi'an, Shaanxi Province Daishi Qi, Feng Sun, Xuwei Chen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6364938/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 13 Aug, 2025 Read the published version in npj Heritage Science → Version 1 posted 13 You are reading this latest preprint version Abstract This study is based on the ink stick unearthed from the tombs of the Northern Song Dynasty (960 CE-1127 CE) in Xi 'an, Shaanxi Province, during which the development of ancient Chinese ink making technology reached its peak. The sample was analyzed by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), energy dispersive analysis (EDS) and microscopic laser Raman spectroscopy (Raman). The sample was identified as pine-soot ink, and animal glue was added in the production process. In addition, lime (CaCO3) for shade drying, lithargite (PbO) for insecticidal effect and jarosite (KFe33+(OH)6(SO4)2), the oxidation product of pyrite (FeS), which is similar to gold in appearance but lower in cost, were also detected in ash and ink stick, fully revealing the production process of pine-soot ink in Song Dynasty. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction As an important writing material, ink plays a very important role in recording and transmitting world history. Unlike liquid ink commonly used in the West 1-5 , ink in ancient China was mostly solid, which is related to its production process. By adding glue to the soot particles and repeatedly pounding them to make them tightly bound, it finally took on a solid state. Because of this, ancient Chinese ink can be preserved to this day. Ink stick is a great invention created by ancient Chinese ancestors, famous for its deep color and durability. In China, it is not only the prerequisite and foundation for the application of printing, but also one of the most frequently used pigments in calligraphy and painting 6 , which has had a profound impact on the inheritance and spread of Chinese civilization. Ancient Chinese ink sticks were generally made of a combination of soot, animal glue and other additives 7 . Among them, soot was the main substance, and according to the different sources of soot, the ink can be categorized into two main groups: pine-soot ink and oil-soot ink. The soot of the former group was obtained by incomplete combustion of pine branches, while the soot of the latter group came from incomplete combustion of oils and fats 8 . In China, the earliest ink found archaeologically is a pine-soot ink stick from the late Warring States period (战国晚期) (306-221 BCE) 9 , before which naturally-obtained charcoal black was mostly used as a black pigment 10 . The ink sticks of this period were handmade, but the craftsmanship was relatively crude. By the Eastern Han Dynasty (东汉) (25-220 CE), with the widespread use of paper, the development of pine-soot ink had begun to take shape, and the shape of the ink stick was gradually regularized. During the Wei and Jin Dynasties (魏晋) (220-420 CE), pine-soot ink became the main ink product of the time, and the first ink recipe in Chinese history appeared during the Northern and Southern Dynasties (南北朝) (420-589 CE) 11 . Thereafter, the influence of the Tang Dynasty (唐) (618-907 CE) literati's preference for writing books and the widespread use of printing during the Northern Song Dynasty (北宋) (960-1127 CE) further promoted the development of the ink-making industry. To the Song Dynasty (宋) (960-1279 AD), especially in the Northern Song Dynasty (北宋) (960 - 1127 CE), the production process of pine-soot ink has been very mature. Specifically manifested as: 1) the emergence of a large number of highly skilled ink-making craftsmen and many monographs summarizing the ink-making process; 2) the increase in the production of pine-soot ink, from individual homemade to mass production; 3) the government set up a special ink-making institutions. However, due to the unavailability of pine wood, pine-soot ink was gradually replaced by oil-soot ink after the Song Dynasty (宋) 8 . Nonetheless, pine-soot ink has occupied China for nearly 2,000 years, and was the beginning of manual ink-making in ancient China, providing a wealth of experience in the development of ancient oil-soot ink as well as modern ink-making processes. Previously, some scholars have already studied the composition and process of ancient Chinese ink sticks 12,13 , however, since these samples are all relatively early in date, mainly focusing on the Han-Wei period (汉魏时期) (202 BCE-317 CE), they can only reflect the ink-making process in early ancient China. In addition, current research on ancient Chinese ink sticks mainly focuses on organic matter. For example, in 2012, Shuya Wei et al. used pyrolysis gas chromatography and mass spectrometry (Py-GC/MS) to analyze an ink stick unearthed from the Leitiao (雷鋽) tomb in the Eastern Jin (东晋) Dynasty in Nanchang (南昌), China, and detected organic additives such as borneol (冰片) and cedar oil 14 . In 2018, Li Guan et al. used infrared spectral analysis and gas chromatography-mass spectrometry (GC-MS) and other methods to analyze an ancient ink sample unearthed from the tomb of the Haihunhou (海昏侯) of the Western Han Dynasty (西汉) (202 BCE-8 CE) in Nanchang (南昌), Jiangxi (江西) Province, and proved that it was an early artificially produced pine-soot ink stick; they also compared it with the modern pine-soot ink, and deduced that animal glue might have been added to it 15 . In 2021, Na Yao et al. conducted scientific and technological analysis of an ink stick unearthed from a late Warring States period (战国晚期) (306-221 BCE) tomb in Jiudian (九店), Jiangling (江陵), Hubei (湖北), and combined infrared spectroscopy, transmission electron microscopy, and Py-GC/MS to comprehensively determine that the sample was a pine-soot ink, and camphor and cedar oil were detected 16 . As for the exploration of inorganic components in ancient ink sticks, as early as 1997, Huansheng Cheng et al. had already found higher contents of Ca and Pb elements in ancient ink sticks by using proton induced X-ray emission (PIXE), but did not discuss them in depth 17 . In 2024, Zigang Gao et al. studied modern Chinese ink sticks by using thermogravimetric analysis (TGA) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and also found a higher content of Ca element, which was thought to be caused by the addition of calcium carbonate (CaCO 3 ) to the ink, but did not explain the reason for the presence of calcium carbonate in the ink 18 . In order to fully study the production process of ancient Chinese ink sticks, this study selected the ink stick unearthed from the Northern Song Dynasty (北宋) Tomb M23 at the Xi'an Archaeological Site in Shaanxi (陕西) Province for scientific and technological analysis. The Song Dynasty (宋) occupies a very important position in the history of China's ink production process, and during this period, the development of ancient pine-soot ink reached its peak stage, which contains even more information about the process. The study intends to use scanning electron microscope to observe the micro-morphology of the sample, and Fourier transform infrared spectroscopy to detect the organic component in the sample. Thermogravimetric and Raman analyses will also be performed, in an attempt to combine organic and inorganic analytical methods to reveal information about the ancient Chinese ink-making process from multiple perspectives and to enrich the research in the field of ancient Chinese ink-making process. Reaserch aim Ink is one of the “four treasures of literature (文房四宝)”, which has experienced a long history of development in China. During the Northern Song Dynasty, the production process of pine-soot ink was very complete, and the analysis of this sample can reveal the technical level of ink production at that time, so as to understand the social development of the Northern Song Dynasty. Compared with the previous analytical method which is more inclined to organic matter, thermogravimetric analysis is a new method that has been applied to the study of the ink stick process in recent years 18 , which can understand the proportion of the main raw materials (soot and glue) added in the ink stick, and it is of great significance in revealing the ink-making process in the Northern Song Dynasty. In addition, the microscopic laser Raman technique is now widely used in the field of heritage research 19-23 . Raman spectroscopy probes molecular and crystal lattice vibrations and therefore is sensitive to the composition, bonding, chemical environment, phase, and crystalline structure of the sample material. These characteristics make it an exceptional method for unambiguously identifying materials in any physical form 24 . This study utilized thermogravimetric analysis, Raman analysis and energy spectrum analysis to discover new phenomena in the sample that had not been revealed in previous studies, and the results corresponded to the ink production monographs of the Northern Song Dynasty, which not only proved the reliability of the ink production monographs, but also further illustrated the maturity of the production process of the pine-soot ink in that period. Meterial and methods Materials The sample is from the Northern Song Dynasty (北宋) Fanxiaochong (范孝充) Tomb M23 at the Shaanxi Normal University (陕西师范大学) archaeological site. The photograph of the sample is shown in Fig. 1 . It can be observed that there are obvious cracks on the surface of the sample and the phenomenon of localized flaking, thus exposing the internal condition of the sample. Compared with the whitish surface color and the existence of different degrees of yellow cover, which may be caused by the contact between the sample surface and the soil in the tomb, the internal color of the sample is darker and very uniform, with no obvious contamination. The analyzed samples were taken from the uncontaminated interior of the ink stick. Methods and test conditions Scanning electron microscope (SEM). A high-resolution field emission scanning electron microscope, SU8010, manufactured by Hitachi, Japan, was used to observe the micro-morphological characteristics of the sample soot particles. The test conditions were scattering mode, accelerating voltage of 3 kV, working distance of 9.2 mm, and magnification of 20.0 k×. Due to the fragile nature of the samples, the sample was embedded with resin before the experiment and pasted on conductive adhesive for observation after curing. Fourier-transform infrared spectroscopy (FTIR). LUMOS Fourier transform infrared spectrometer (with ATR accessory) manufactured by Bruker, Germany. The number of background scans was 64, the wave number range was 600 ~ 4000cm − 1 , and the resolution was 2cm − 1 . During the test, a small piece of sample was taken with tweezers, and an appropriate amount of potassium bromide powder was added, ground until it was mixed well and then pressed into a disc with a metal mold, fixed on the sample stage and loaded into the instrument for testing, and the data were analyzed and graphed using Omnic and Origin software. Thermogravimetric analysis (TGA). SDT Q600 V20.9 Build 20 Integrated Thermal Analyzer from TA Instruments, USA. For the experiments, 5 mg of fresh samples were taken, ground into powder and loaded into the alumina crucible for thermal analysis, and tested in an air atmosphere with a gas flow rate of 100 ml/min, the starting and stopping temperatures were set from room temperature to 700 ℃, and the heating rate was 5 ℃/min. After exporting the data, the TG curves were plotted with Origin software and analyzed. Energy dispersive spectroscopy (EDS). X-ACT type X-ray spectrometer from Oxford Instrument, UK, equipped with a VEGA-3XMU scanning electron microscope from TESCAN, Czech Republic, was used to analyze the composition of the ash after thermogravimetric analysis of the sample. Appropriate amount of ash powder was pasted on conductive adhesive and tested under 100× magnification. Micro-laser Raman spectroscopy (Raman). The in Via Qontor micro confocal Raman spectrometer manufactured by Renishaw, UK, is equipped with 532nm, 633nm and 785nm lasers. The experiments were tested with a 532nm laser and the spectral range of the acquisition was 110 ~ 1500cm − 1 with an objective lens magnification of 50×. The Micro-Laser Raman Spectrometer can perform in-situ non-destructive testing at high magnification and realize precise analysis of the sample. Results and discussion Scanning electron microscope analysis results The samples were resin-embedded before the experiment. The micro-morphological characteristics of the soot particles were observed at 20.0k magnification. And the modern pine-soot ink and modern oil-soot ink produced by Shanghai Ink Factory were selected as the standard samples for this experiment. The micrographs are shown in Fig. 2. As can be seen from the figure, the shape of the sample soot particles is nearly spherical, with loose distribution and non-uniform size, and there is the phenomenon of some particles agglomerating and fusing. The size of the sample particles was measured to be around 100 nm on average. At present, the existing studies have shown that the particles of pine-soot ink have the morphology characteristics of nearly spherical, uneven size, and there is the phenomenon of some particles melting, and the particle diameter distribution is around 100 nm; the particles of oil-soot ink are irregular aggregates, the size of which is more uniform, and the particle size is around 30 nm 13,25 . In terms of particle morphology and size, the sample is closer to the characteristics of pine-soot ink. Therefore, the sample is judged to be pine-soot ink based on the scanning electron micrographs. However, more than a thousand years ago, science and technology were not advanced. The ancients needed a high level of craftsmanship to achieve the size of the soot particles in the ink stick to the nanometer level. This is inextricably linked to the process of taking materials, selecting soot and pounding in making ink stick. First of all, the choice of pine wood determines the quality of the soot, during the Eastern Han Dynasty (东汉), Ying shao (应劭) wrote the book called “Han-Guan-Yi (汉官仪)”, which recorded that “The prime minister, the deputy prime minister, the secretary general and the drafter of documents are given one large ink and one small ink from Yu Mi every month (尚书令、仆、丞、郎月赐喻糜大墨一枚、小墨一枚).” 26 . The name “Yu Mi (喻糜)” refers to today's Qianyang (千阳), Shaanxi (陕西) Province, China, which was an important source of fine pine wood at that time. This shows that as late as the Han Dynasty, the ancients already had a clear knowledge of the origin of fine pine wood 8 . Next is the collection of soot, in order to better enrich the soot particles, the firing is usually carried out in a closed soot kiln, which can be categorized into flat kiln and vertical kiln according to the different shapes. Due to the light weight of the soot particles, it will be attached to the kiln wall, and the top soot particles are smaller and lighter, therefore, the “far soot” and “top soot” particles in the kiln are the finest, and the quality of the ink stick made from this kind of soot is the best 27 . In the Ming Dynasty (明), the book “Tian-Gong-Kai-Wu (天工开物)” written by Song Yingxing (宋应星) also recorded that in the process of firing the soot, “the soot located in the last one or two sections is the purest, and is taken as the material for the finest ink stick (靠尾一二节者为清烟, 取入佳墨为料)” 28 . In addition, pounding is also an important step in the ink stick production process. In ancient times, the production of ink sticks have “add a small amount of glue and pound tens of thousands of times (轻胶万杵)” said, only after repeated pounding, can make the soot particles and animal glue fully combined, the production of ink sticks will be tougher 29 . In the Northern Wei period (北魏时期) (386–534 CE), Jia Sixie (贾思勰) wrote the book “Qi-Min-Yao-Shu (齐民要术)”, which is one of the earliest surviving works on agriculture in China. The book recorded a large number of production methods and techniques, including the “Combined ink method (合墨法)”, mentioned before molding, ink needs to go through the process of “Pounding 30,000 times, the more times more good (捣三万杵, 杵多益善)” 30 . Furthermore, in the “Tian-Gong-Kai-Wu (天工开物)”, Song Yingxing (宋应星) also pointed out that the ink “After adding the animal glue, the number of whacks determines the hardness of the ink stick (和胶之后, 以捶敲多寡分脆坚)”, reflecting the importance of whacks to the ink. Fourier-transform infrared spectroscopy analysis results For the experiment, fresh samples were taken from the inside of the ink stick. Appropriate amount of potassium bromide powder was added for grinding, mixed well and pressed for testing, and the analytical results are shown in Fig. 3. The broad peak at 3665 cm − 1 in the figure represents the stretching vibration of -OH 31 , which may be related to the moisture in the sample; 1778 cm − 1 assigned to the carbonyl stretching mode of the ester group (vC = O) 32 , indicating the presence of lipid components 33 ;1688 cm − 1 assigned to the C = O stretching vibration of peptide bonds, which can be attributed to the polypeptide chains from ancient proteinaceous materials 34 ; and the absorption peak near 1500 cm − 1 belongs to the C-N-H bending vibration 35 , with the C-N-H being mostly assigned to protein Amide II 36 . Combining the above information, it can be determined that the sample contain animal glue. Animal glue is an adhesive, the main components of which are gelatin and residues of other proteins collagen, keratin or elastin. It can be made from bones, hides and the intestines of animals (fish, sheep, cattle, horses, etc.). Animal skins and bones are heated with hot water to gather the gelatine in them, cooled and dried to make animal glue 37 . Because of its easy accessibility, convenient processing and low cost, it was a commonly used type of glue by ancient Chinese artisans 38 . Among many animal glues, deer glue, cow glue, fish glue and egg glue were commonly used by ancient Chinese 39 . And depending on the actual situation, the ancients also mixed many kinds of animal glues 40 . Due to the cracking and peeling of the sample surface, the organic matter in the ink stick will be partially lost, so the infrared spectra of the sample is not very typical, but the above infrared characteristic peaks can be used as a basis for judging that the sample contains organic binding medium. Glue also plays a very important role in the production of ink sticks. Chao Jiyi (晁季一), a scholar of the Song Dynasty, once wrote in his book “Mo-Jing (墨经)” that “For all ink sticks, glue is the most important. If you have the best soot but the glue method is not appropriate, the ink sticks will not be good. If you get the right glue method, even if you don't have that good soot, you can make good ink sticks (凡墨, 胶为大。有上等煤而胶不如法, 墨亦不佳。如得胶法, 虽次煤能成善墨)” 41 . The addition of animal glue can not only coagulate the soot particles into a solid form of ink stick, which plays a role in molding, but also make the ink stick not easy to appear particles precipitation after grinding with water, which is convenient for writing. In addition, it can also enhance the bond between ink and paper, which is not easy to fall off after writing, and is conducive to the long-term preservation of calligraphy and painting works 27 . The infrared spectral analysis confirms that animal glue was added to the sample during the production process, which is an important reason why the ancient ink sticks retained their original form after being buried in tombs for more than a thousand years. Thermogravimetric analysis results The ink sticks are mainly composed of soot and glue, which have large differences in thermal decomposition and weight loss temperatures. Therefore thermogravimetric analysis can reflect their compositional specific gravity 42 . For the experiment, 5 mg of uncontaminated sample inside the ink stick was selected and ground into powder to test the thermal decomposition and weight loss process of the sample under air atmosphere. According to the variation of the thermogravimetric curve, the weight loss process of the sample is roughly divided into three stages: ⅰ) loss of water; ⅱ) thermal cracking of molecules such as glue material; ⅲ) oxidative combustion of carbon particles 18 . The results of thermogravimetric analysis are shown in Fig. 4. By calculating the weight percentages of the glue stage and the soot stage, the glue to soot ratio in the sample was estimated to be 0.16 (glue/soot = 10%/63% ≈ 0.16.). Based on ink-making monographs from the Northern Song Dynasty, such as the “Mo-Jing (墨经)”, the “Wen-Fang-Si-Pu (文房四谱)” and the “Mo-Pu-Fa-Shi (墨谱法式)”. These books recorded the methods and steps of the ancient method of ink production, and also mentioned the amount of glue and soot material many times. The proportion of glue used in different ancient ink-making methods is detailed in Table 1. Ancient Chinese weight units continued the weights and measures system of the Qin Dynasty (秦), with one catty (斤) being about sixteen taels (两), which can be converted to the glue to soot ratio of about 0.3 recorded in these monographs. In comparison, the proportion of glue to soot in the sample was significantly lower, which may be related to the gradual aging and loss of organic glue caused by the long burial time of the ink stick. Table 1 ัGlue to soot ratios of different methods of making ink sticks in ancient China Monograph Author Method Dosage Glue/Soot Ratio “Mo-Jing” (墨经) 41 Chao Jiyi (晁季一) Jia Sixie’s Method (贾思勰墨法) “One catty of soot, five taels of glue” (煤一斤, 用胶五两) 5/16 0.31 “Wen-Fang-Si-Pu” (文房四谱) 43 Su Yijian (苏易简) Wei Zhongjiang’s Method (韦仲将墨法) “One catty of fine soot, five taels of good glue” (烟一斤以上, 好胶五两) 5/16 0.31 “Mo-Pu-Fa-Shi” (墨谱法式) 44 Li Xiaomei (李孝美) Ancient Method (古墨墨法) “Six taels of glue, one catty of soot” (胶六两, 煤一斤) 6/16 0.38 “Five taels of antler gelatin, one catty of coal” (鹿角胶五两, 煤一斤) 5/16 0.31 Oil-soot ink Method (油烟墨墨法) “Four taels of glue, one catty of soot” (胶四两, 煤一斤) 4/16 0.25 “Five taels of rubber, one catty of coal” (胶五两, 煤一斤) 5/16 0.31 Energy dispersive spectroscopy analysis results It can be observed from Fig. 4 that the sample still has about 17% residue at the end of thermogravimetric analysis. The residual weight in the sample is related to the impurities in the ink stick that are not easily combustible, since moisture, glue and soot can all be decomposed when heated in an air atmosphere 18 . The ancients would have added other additives to the ink-making process, and the study used energy dispersive spectroscopy to analyze the composition of the residual ash. At the same time, the original composition of the ink stick sample without thermogravimetric analysis was also analyzed, and the results can be used as a comparison of the ash elemental data, and the two corroborate each other, so as to fully reveal the elements other than C, H and N in the ink stick, and further excavating the information on the production process of the pine-soot ink in the Northern Song Dynasty. Take the appropriate amount of ash powder and ink stick internal sample pasted on the conductive adhesive, magnification 100×. Before the test, ash and ink stick were not sprayed with gold and carbon, elemental data are normalized, the results are detailed in Table 2, the specific test points are shown in Fig. 5. Table 2 ัThe EDS analysis results of ash and ink stick (Wt/%) Ash Ink stick Element 1 2 3 4 5 1 2 3 4 5 C 13.25 11.45 11.58 10.33 14.88 53.40 77.46 79.17 79.22 79.15 O 46.23 41.17 43.79 42.43 44.06 17.18 11.17 15.77 17.58 16.70 Mg 1.78 1.48 1.70 1.66 1.69 0.12 0.25 0.21 0.16 0.17 Al 0.95 0.43 0.56 0.38 3.02 1.17 0.11 0.11 0.04 0.08 Si 1.62 0.96 0.71 0.65 4.42 0.11 0.27 0.15 0.06 0.25 S 0.16 0.25 0.22 0.47 0.14 0.02 0.04 0.01 0.03 / Cl / / / / / 0.08 0.10 / / / K 0.21 0.19 0.11 0.12 1.25 0.12 0.03 0.04 0.02 0.04 Ca 24.78 31.50 28.88 32.45 19.29 22.55 7.84 3.35 2.13 2.58 Fe 0.26 0.40 0.34 0.17 2.86 0.71 0.07 0.07 0.01 0.03 Cu 2.01 2.43 2.19 2.33 1.64 3.44 0.64 0.23 0.15 0.22 Pb 8.75 9.76 9.90 9.01 6.74 1.10 2.02 0.89 0.60 0.78 The results show that the composition of the ash is mainly Ca element and O element, which was related to the fact that a certain amount of CaCO 3 was added to the ink stick during the preparation process, which was transformed into CaO after high-temperature decomposition 18 . In addition, a certain amount of carbon is present in the ash. During the heating process, limited by the reaction rate, element C may not be completely oxidized to CO 2 at high temperatures, so a certain amount of element C remains 18 . The higher content of element Pb reflects the information about the sample making process. The presence of Cu element may be related to the metal burials in the tombs, but there are also related studies that show that Cu can play a role in increasing the color in the ancient ink 12 . The ash also includes trace amounts of Si, Al, and Mg, which are also found in the ink stick and are caused by contact with the soil in the burial. In addition, very trace amounts of the Cl element were detected in the ink stick, presumably the samples were affected by soluble salts in the burial environment. Microscopic laser Raman spectroscopy analysis results To further explore the information about the additives in the sample, the study utilized microscopic laser Raman spectroscopy to analyze the ash as well as the ink stick for the first time. The experiment was conducted by taking appropriate amounts of ash powder and uncontaminated samples inside the ink stick under a 50× objective lens, and it was seen that there were obvious white particles and yellow particles in both the ash and the ink stick. These particles have regular shapes, clear boundaries, and uniform colors. Combined with the fact that ancient craftsmen often added other additives to the ink sticks, the study suggests that these particles were added artificially after grinding, which could reflect information on the process of making pine-soot ink. The test was performed with a 532nm laser, the test points and results are shown below. After analysis, the gray-white particles in the ash and ink stick are limestone (CaCO 3 ), the yellow particles are lithargite (PbO) and the silver-white particles are jarosite (KFe 3 3+ (OH) 6 (SO 4 ) 2 ). The analytical results correspond exactly to the elemental data. Limestone (CaCO 3 ). Raman results show that the gray-white particles in the ash have obvious peak at 1086 cm − 1 ; those of the ink stick also have peaks at 152 cm − 1 , 277 cm − 1 , 713 cm − 1 and 1086 cm − 1 , which are characteristic peaks of limestone (CaCO 3 ), as shown in Fig. 6. According to ancient ink-making monographs, the production of ancient ink sticks included the following steps: “selecting materials (选材), obtaining soot (取烟), sieving (罗筛), adding glue (和胶), adding medicine (入药), steaming (蒸剂), pounding (杵捣), rolling into balls (擀丸), molding (制样) and shade-drying (荫干)” 45 . Among them, the lime used for shade drying is the main reason for the presence of calcium carbonate in the ink stick. In the process of making ink sticks, due to the water added to the decoction of glue, in order to avoid deformation and cracking in the drying process of the ink stick has been molded, the ancient craftsmen in the addition of glue will intentionally control the humidity of the ink, “rather dry than wet (宁干勿湿)” 44 . And will be put the ink stick into furnace ash, lime or wheat bran, these substances have hygroscopicity, the ancients took advantage of this property so that the ink sticks can slowly shade dry 41 , this step was also called “put into the ash (入灰)”. In the Ming Dynasty (明), “Fang-Shi-Mo-Pu (方氏墨谱)” also recorded that the ink stick “is put into the ash to remove the smell of glue, and has a beneficial effect on the color of the ink stick (纳之灰中能去胶气而益墨色)”, “dries easily in the ash without cracking (置灰中易干而不溃)” 46 . After the ink stick was put into the ash, “it must not be exposed to the wind or it will break (不可见风, 见风墨断)”, the whole shade drying process needs to be carried out in a closed and windless environment. Then, after a period of time, “Through the ink sticks hit each other, if the sound is crisp and loud, it can be taken out of the ash (以墨相击, 其声干响, 方可出灰)”, and then use a brush to clean up the ash on the ink stick 45 . Accordingly, it can be inferred that the sample also went through the step of “put into the ash (入灰)”, and was shade-dried with lime. In the process of shade drying, due to the closed environment without wind, the lime powder will gradually penetrate into the ink stick, which leads to the presence of a high content of Ca and O elements in the sample. Lithargite (PbO). The study utilized microscopic laser Raman spectroscopy to analyze the yellow particles in the ash and ink stick, and the results are shown in Fig. 7. The results show that the main peaks of the yellow particles are all located near 145 cm − 1 , indicating that their main component is lead oxide (PbO) 47 , which is also known as “lithargite (密陀僧)”. In addition, the yellow particles in the ash also show peaks at 200 cm − 1 , 290 cm − 1 , 397 cm − 1 , 508 cm − 1 and 635 cm − 1 corresponding to lead dioxide (PbO 2 ) 48 . This is due to the fact that the thermogravimetric analysis was carried out in an air atmosphere and the lead oxide particles in the ink stick were gradually oxidized to lead dioxide during the slow heating process. Lead was one of the first few metals recognized by mankind, and in the process of smelting lead, the ancient Chinese smelted artificial compounds of lead such as lead tetroxide (铅丹) and lithargite (密陀僧) 49 . Lithargite is lead oxide (PbO), because its color is generally yellow, so it is also known as “lead yellow (铅黄)”, in cultural relics are mainly used as yellow pigments 50 . The famous Tang Dynasty(唐) medical book “Xin-Xiu-Ben-Cao (新修本草)” recorded the source of lithargite in ancient China, and believed that before the Tang Dynasty, lithargite “came from the country of Persia (来自波斯国)” 51 . However, archaeological data show that as early as the Qin Dynasty (秦), ancient Chinese were able to synthesize lead oxide artificially and used it as pigment to paint the surface of terracotta figurines 52 . By the Tang Dynasty (唐), the use of lithargite as a color pigment had become very common 49 . Therefore, it is no coincidence that lithargite appears in the ink stick of the Song Dynasty (宋). The “Xin-Xiu-Ben-Cao (新修本草)” also recorded that lithargite had insecticidal and fungistatic properties, and that it could be used in medicine to “treat sores and subdue swellings and poisons” 51 . In ancient times, in order to further improve the performance of ink sticks, craftsmen would add medicinal herbs and spices, which was called “adding medicine (入药)”. For example, the addition of borneol (龙脑) and musk (麝香) can increase the aroma of ink stick; the addition of gleditsia sinensis (皂角) can help remove moisture and the addition of dioscorea bulbifera (黄药) can make the ink stick grinding soundless 46 . Among them, borneol is also called “bing piàn (冰片)”, which was documented in the “Ben-Cao-Gang-Mu (本草纲目)” as having antimicrobial properties. In 2011, Shuya Wei et al. detected it in ink stick excavated from Leitiao (雷鋽) tomb in the Eastern Jin Dynasty (东晋) using pyrolysis gas chromatography and mass spectrometry (Py-GC/MS) and concluded that it was added to prevent biological attack 53 . Therefore, the addition of lithargite, which also has an insecticidal effect, to the ink stick was also to prevent the ink stick from being attacked by organisms and to facilitate its long-term preservation. Jarosite (KFe 3 3+ (OH) 6 (SO 4 ) 2 ). The silver-white particles in the ash and ink stick were analyzed to be jarosite 54 . The Raman peak positions are shifted to some extent due to environmental factors 55 , but the overall trend of the spectra are the same and correspond to the elemental data. And due to the presence of organic matter in the ink stick, the Raman signal was interfered by fluorescence to a certain extent, and only the main peaks 210 cm − 1 and 460 cm − 1 of jarosite with stronger signals are detected in the ink stick 56 . The Raman results are shown in Fig. 8. Jarosite is a member of the alum group with the chemical formula KFe 3 3+ (OH) 6 (SO 4 ) 2 , which is a product of the oxidation of pyrite. It was once discovered during the mining of silver, gold and lead ores 57 and has been used in metallurgical and environmental fields due to its strong adsorption capacity 58,59 . However, the natural sources of jarosite are relatively limited, and most of the jarosite used for research is synthesized under laboratory conditions, which are mostly different from those in nature, resulting in the fact that the crystal structures of the synthesized minerals and the natural minerals may be the same, but the molecular structures may not be the same. Therefore, the spectra of the synthesized minerals are not necessarily the same as those of the natural minerals 56 , which is the main reason for the shift in the peak position of the jarosite in the sample. In cultural relics, jarosite can be used as a yellow pigment 60,61 , but it is not common, so there are fewer studies on jarosite in cultural relics, and the existing analytical work is more focused on foreign countries. The detection of jarosite in the sample not only provides new data for the study of ancient Chinese ink sticks, but also complements the study of jarosite in the field of cultural relics. The main component of pyrite is iron sulfide (FeS 2 ), which is easily oxidized slowly in acidic and anoxic environments to produce jarosite 62,63 , which coincides with the burial environment of the sample, so the presence of jarosite suggests that pyrite may have been added to the sample at the beginning of its production, and then slowly oxidized to jarosite in the prolonged burial environment. Pyrite has a similar appearance to gold, and many people would mistake pyrite for gold, commonly known as “fool's gold (愚人金)” 64 . In order to increase the luster of the ink sticks, ancient craftsmen also added substances such as cinnabar and gold foil during the ink-making process 45 . The ancient Chinese craftsmen chose pyrite, which is very similar in appearance to gold but costs much less than gold, indicates that by the Song Dynasty, craftsmen not only mastered the process of making ink sticks, but also could reduce the production cost by adjusting the type of material used to make them, further proving that the ink-making craftsmen of the Song Dynasty already possessed a high level of technology. Conclusion Based on the scanning electron microscope results, it can be determined that the sample is pine-soot ink. And animal glue was detected in the sample using fourier transform infrared spectroscopy. Since the weight loss stage of the sample is distinct in the air atmosphere, by calculating the weight percentage of the glue stage and the soot stage, it can be concluded that the glue to soot ratio of the sample is 0.16, which is lower than that of the ratio of 0.3 recorded in the ancient books, and it is presumed that aging and partial loss of the glue in the sample occurred in the long term burial process. To further explore the production process, the composition of the ash and ink stick was analyzed using energy dispersive spectroscopy and microscopic laser raman spectroscopy, which detected lime for shade drying (CaCO 3 ), lithargite with insecticidal properties (PbO) and jarosite, an oxidized product of pyrite that can increase the luster of the ink stick (KFe 3 3+ (OH) 6 (SO 4 ) 2 ). The above information fully reveals the craftsmanship of the Northern Song Dynasty pine-soot ink from multiple angles, proving that craftsmen of this period not only mastered the ink-making process, but also were able to reduce production costs by adjusting the types of materials. This sample exemplifies the development of the Song dynasty's pine-soot ink production process to its peak. The study is the first time to conduct scientific and technical analysis on the ash content of the ink stick after thermogravimetry, and dig deeper into the information of inorganic components. It corroborates and supplements the records on ink in ancient literature, provides new data for the study of the production process of pine-soot ink, and enriches the study of the ancient Chinese ink-making process, thus promoting the continuation and development of the traditional Chinese craftsmanship. Declarations Data availability The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Acknowledgements Thanks to Shaanxi Academy of Archaeology for providing the sample. This work has been supported by the National Natural Science Foundation of China (NO. 22101226), 111 project (D18004). Author contributions Daishi Qi performed all experimental tests, interpreted the data, and wrote the manuscript. Feng Sun provided support and guidance for this study. Xuwei Chen provided the sample used in the study. All authors read and approved the final version. Competing interests The authors declare no competing interests. Additional information Correspondence and requests for materials should be addressed to Feng Sun. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6364938","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":447001096,"identity":"d8aa75d0-ea67-4072-aa6d-ceaef75023dc","order_by":0,"name":"Daishi Qi","email":"","orcid":"","institution":"China-Central Asia “the Belt, Northwest University","correspondingAuthor":false,"prefix":"","firstName":"Daishi","middleName":"","lastName":"Qi","suffix":""},{"id":447001097,"identity":"34420393-8032-4215-8999-14976d046959","order_by":1,"name":"Feng Sun","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYJCCD0AsB2GyEaeDcQaQMCZdS2ID0VrkZ+QebPi4ozZ9u0SOAcOHssMM/LMb8GsxuJGX2DjzzPHcnTNyDBhnnDvMIHHnAAEtEjnmj3nbjuVuuJ1jwMzbdhgokkDIYTmGzX/bjqUbgLT8JUYLww2gFsa2mgSwFkZitBiceWPY2Nt2wHDD/WcFB3vOpfNI3CDksPYcw4afbXXyBmcOb3zwo8xajn8GIYdBwGEweQCIeYhSDwR1xCocBaNgFIyCkQgAG2FHEM+bI3IAAAAASUVORK5CYII=","orcid":"","institution":"China-Central Asia “the Belt, Northwest University","correspondingAuthor":true,"prefix":"","firstName":"Feng","middleName":"","lastName":"Sun","suffix":""},{"id":447001098,"identity":"242ae630-894a-4acb-a9f1-a5d887da5f2a","order_by":2,"name":"Xuwei Chen","email":"","orcid":"","institution":"Shaanxi Academy of Archaeology","correspondingAuthor":false,"prefix":"","firstName":"Xuwei","middleName":"","lastName":"Chen","suffix":""}],"badges":[],"createdAt":"2025-04-03 01:53:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6364938/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6364938/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s40494-025-01976-5","type":"published","date":"2025-08-13T15:57:46+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":81305713,"identity":"3b016841-60ba-4f2f-be1b-76dbfcfc3e43","added_by":"auto","created_at":"2025-04-24 14:39:36","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":235216,"visible":true,"origin":"","legend":"\u003cp\u003ePhotographs of the sample: (a) Front of the sample; (b) Back of the sample\u003c/p\u003e","description":"","filename":"Fig.1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6364938/v1/4eb3450bd0d7cf233b7a1474.jpg"},{"id":81304398,"identity":"b072a659-333d-41a4-85d9-3eb0b5148fd9","added_by":"auto","created_at":"2025-04-24 14:31:36","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":485131,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscope photographs: (a) Sample; (b) Modern pine-soot ink; (c) Modern oil-soot ink\u003c/p\u003e","description":"","filename":"Fig.2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6364938/v1/9611ea7bdf4685b66080c66f.jpg"},{"id":81304393,"identity":"2d4695d2-2e1e-4f2d-a0b4-aec841062272","added_by":"auto","created_at":"2025-04-24 14:31:36","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":289249,"visible":true,"origin":"","legend":"\u003cp\u003eInfrared spectral analysis result of the sample\u003c/p\u003e","description":"","filename":"Fig.3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6364938/v1/871f63ad452943fbfae5e607.jpg"},{"id":81306596,"identity":"25eae1c8-1318-4447-a9cf-adf9c86ed9c9","added_by":"auto","created_at":"2025-04-24 14:47:36","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":297388,"visible":true,"origin":"","legend":"\u003cp\u003eThermogravimetric analysis results of the sample\u003c/p\u003e","description":"","filename":"Fig.4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6364938/v1/6569b724c939a9f57bcc50f3.jpg"},{"id":81304396,"identity":"4bafad6f-18f9-4e08-980b-d7e4d405867f","added_by":"auto","created_at":"2025-04-24 14:31:36","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1518841,"visible":true,"origin":"","legend":"\u003cp\u003eTest points for EDS analysis: (a) ash; (b) ink stick\u003c/p\u003e","description":"","filename":"Fig.5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6364938/v1/2a0a7e8fb34ccbee2b2b271c.jpg"},{"id":81304392,"identity":"b7e88012-0185-48a7-9f53-d6c876a41ee6","added_by":"auto","created_at":"2025-04-24 14:31:36","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":1687092,"visible":true,"origin":"","legend":"\u003cp\u003eLimestone (CaCO\u003csub\u003e3\u003c/sub\u003e)\u003c/p\u003e","description":"","filename":"Fig.6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6364938/v1/54a012f58588048e0647278a.jpg"},{"id":81305717,"identity":"756a94d4-d217-4dab-a95c-274d6a0c8dd5","added_by":"auto","created_at":"2025-04-24 14:39:36","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1602438,"visible":true,"origin":"","legend":"\u003cp\u003eLithargite (PbO)\u003c/p\u003e","description":"","filename":"Fig.7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6364938/v1/5ad9794dea37e08ac999fe66.jpg"},{"id":81304401,"identity":"fd6fe994-a570-4012-979b-be1648a33251","added_by":"auto","created_at":"2025-04-24 14:31:36","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1719134,"visible":true,"origin":"","legend":"\u003cp\u003eJasorite (KFe\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e3+\u003c/sup\u003e(OH)\u003csub\u003e6\u003c/sub\u003e(SO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e","description":"","filename":"Fig.8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6364938/v1/820f169bbb709b85d2654954.jpg"},{"id":89310566,"identity":"e48f52c1-8dae-4167-b6c9-b7e0190f9b65","added_by":"auto","created_at":"2025-08-18 16:08:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8893365,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6364938/v1/34b58365-df5a-472f-a811-7e6c98da5fd1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Scientific and technological analysis and research on the ink stick unearthed from the tomb of Fanxiaochong of the Northern Song Dynasty in Xi'an, Shaanxi Province","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAs an important writing material, ink plays a very important role in recording and transmitting world history. Unlike liquid ink commonly used in the West\u003csup\u003e1-5\u003c/sup\u003e, ink in ancient China was mostly solid, which is related to its production process. By adding glue to the soot particles and repeatedly pounding them to make them tightly bound, it finally took on a solid state. Because of this, ancient Chinese ink can be preserved to this day. Ink stick is a great invention created by ancient Chinese ancestors, famous for its deep color and durability. In China, it is not only the prerequisite and foundation for the application of printing, but also one of the most frequently used pigments in calligraphy and painting\u003csup\u003e6\u003c/sup\u003e, which has had a profound impact on the inheritance and spread of Chinese civilization.\u003c/p\u003e\n\u003cp\u003eAncient Chinese ink sticks were generally made of a combination of soot, animal glue and other additives\u003csup\u003e7\u003c/sup\u003e. Among them, soot was the main substance, and according to the different sources of soot, the ink can be categorized into two main groups: pine-soot ink and oil-soot ink. The soot of the former group was obtained by incomplete combustion of pine branches, while the soot of the latter group came from incomplete combustion of oils and fats\u003csup\u003e8\u003c/sup\u003e. In China, the earliest ink found archaeologically is a pine-soot ink stick from the late Warring States period (战国晚期) (306-221 BCE)\u003csup\u003e9\u003c/sup\u003e, before which naturally-obtained charcoal black was mostly used as a black pigment\u003csup\u003e10\u003c/sup\u003e. The ink sticks of this period were handmade, but the craftsmanship was relatively crude. By the Eastern Han Dynasty (东汉) (25-220 CE), with the widespread use of paper, the development of pine-soot ink had begun to take shape, and the shape of the ink stick was gradually regularized. During the Wei and Jin Dynasties (魏晋) (220-420 CE), pine-soot ink became the main ink product of the time, and the first ink recipe in Chinese history appeared during the Northern and Southern Dynasties (南北朝) (420-589 CE)\u003csup\u003e11\u003c/sup\u003e. Thereafter, the influence of the Tang Dynasty (唐) (618-907 CE) literati\u0026apos;s preference for writing books and the widespread use of printing during the Northern Song Dynasty (北宋) (960-1127 CE) further promoted the development of the ink-making industry. To the Song Dynasty (宋) (960-1279 AD), especially in the Northern Song Dynasty (北宋) (960 - 1127 CE), the production process of pine-soot ink has been very mature. Specifically manifested as: 1) the emergence of a large number of highly skilled ink-making craftsmen and many monographs summarizing the ink-making process; 2) the increase in the production of pine-soot ink, from individual homemade to mass production; 3) the government set up a special ink-making institutions. However, due to the unavailability of pine wood, pine-soot ink was gradually replaced by oil-soot ink after the Song Dynasty (宋)\u003csup\u003e8\u003c/sup\u003e. Nonetheless, pine-soot ink has occupied China for nearly 2,000 years, and was the beginning of manual ink-making in ancient China, providing a wealth of experience in the development of ancient oil-soot ink as well as modern ink-making processes.\u003c/p\u003e\n\u003cp\u003ePreviously, some scholars have already studied the composition and process of ancient Chinese ink sticks\u003csup\u003e12,13\u003c/sup\u003e, however, since these samples are all relatively early in date, mainly focusing on the Han-Wei period (汉魏时期) (202 BCE-317 CE), they can only reflect the ink-making process in early ancient China. In addition, current research on ancient Chinese ink sticks mainly focuses on organic matter. For example, in 2012, Shuya Wei et al. used pyrolysis gas chromatography and mass spectrometry (Py-GC/MS) to analyze an ink stick unearthed from the Leitiao (雷鋽) tomb in the Eastern Jin (东晋) Dynasty in Nanchang (南昌), China, and detected organic additives such as borneol (冰片) and cedar oil\u003csup\u003e14\u003c/sup\u003e. In 2018, Li Guan et al. used infrared spectral analysis and gas chromatography-mass spectrometry (GC-MS) and other methods to analyze an ancient ink sample unearthed from the tomb of the Haihunhou (海昏侯) of the Western Han Dynasty (西汉) (202 BCE-8 CE) in Nanchang (南昌), Jiangxi (江西) Province, and proved that it was an early artificially produced pine-soot ink stick; they also compared it with the modern pine-soot ink, and deduced that animal glue might have been added to it\u003csup\u003e15\u003c/sup\u003e. In 2021, Na Yao et al. conducted scientific and technological analysis of an ink stick unearthed from a late Warring States period (战国晚期) (306-221 BCE) tomb in Jiudian (九店), Jiangling (江陵), Hubei (湖北), and combined infrared spectroscopy, transmission electron microscopy, and Py-GC/MS to comprehensively determine that the sample was a pine-soot ink, and camphor and cedar oil were detected\u003csup\u003e16\u003c/sup\u003e. As for the exploration of inorganic components in ancient ink sticks, as early as 1997, Huansheng Cheng et al. had already found higher contents of Ca and Pb elements in ancient ink sticks by using proton induced X-ray emission (PIXE), but did not discuss them in depth\u003csup\u003e17\u003c/sup\u003e. In 2024, Zigang Gao et al. studied modern Chinese ink sticks by using thermogravimetric analysis (TGA) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and also found a higher content of Ca element, which was thought to be caused by the addition of calcium carbonate (CaCO\u003csub\u003e3\u003c/sub\u003e) to the ink, but did not explain the reason for the presence of calcium carbonate in the ink\u003csup\u003e18\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eIn order to fully study the production process of ancient Chinese ink sticks, this study selected the ink stick unearthed from the Northern Song Dynasty (北宋) Tomb M23 at the Xi\u0026apos;an Archaeological Site in Shaanxi (陕西) Province for scientific and technological analysis. The Song Dynasty (宋) occupies a very important position in the history of China\u0026apos;s ink production process, and during this period, the development of ancient pine-soot ink reached its peak stage, which contains even more information about the process. The study intends to use scanning electron microscope to observe the micro-morphology of the sample, and Fourier transform infrared spectroscopy to detect the organic component in the sample. Thermogravimetric and Raman analyses will also be performed, in an attempt to combine organic and inorganic analytical methods to reveal information about the ancient Chinese ink-making process from multiple perspectives and to enrich the research in the field of ancient Chinese ink-making process.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eReaserch aim\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInk is one of the \u0026ldquo;four treasures of literature (文房四宝)\u0026rdquo;, which has experienced a long history of development in China. During the Northern Song Dynasty, the production process of pine-soot ink was very complete, and the analysis of this sample can reveal the technical level of ink production at that time, so as to understand the social development of the Northern Song Dynasty. Compared with the previous analytical method which is more inclined to organic matter, thermogravimetric analysis is a new method that has been applied to the study of the ink stick process in recent years\u003csup\u003e18\u003c/sup\u003e, which can understand the proportion of the main raw materials (soot and glue) added in the ink stick, and it is of great significance in revealing the ink-making process in the Northern Song Dynasty. In addition, the microscopic laser Raman technique is now widely used in the field of heritage research\u003csup\u003e19-23\u003c/sup\u003e. Raman spectroscopy probes molecular and crystal lattice vibrations and therefore is sensitive to the composition, bonding, chemical environment, phase, and crystalline structure of the sample material. These characteristics make it an exceptional method for unambiguously identifying materials in any physical form\u003csup\u003e24\u003c/sup\u003e. This study utilized thermogravimetric analysis, Raman analysis and energy spectrum analysis to discover new phenomena in the sample that had not been revealed in previous studies, and the results corresponded to the ink production monographs of the Northern Song Dynasty, which not only proved the reliability of the ink production monographs, but also further illustrated the maturity of the production process of the pine-soot ink in that period.\u003c/p\u003e\n"},{"header":"Meterial and methods","content":"\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003eMaterials\u003c/h2\u003e \u003cp\u003eThe sample is from the Northern Song Dynasty (北宋) Fanxiaochong (范孝充) Tomb M23 at the Shaanxi Normal University (陕西师范大学) archaeological site. The photograph of the sample is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. It can be observed that there are obvious cracks on the surface of the sample and the phenomenon of localized flaking, thus exposing the internal condition of the sample. Compared with the whitish surface color and the existence of different degrees of yellow cover, which may be caused by the contact between the sample surface and the soil in the tomb, the internal color of the sample is darker and very uniform, with no obvious contamination. The analyzed samples were taken from the uncontaminated interior of the ink stick.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eMethods and test conditions\u003c/h2\u003e \u003cp\u003e \u003cb\u003eScanning electron microscope (SEM).\u003c/b\u003e A high-resolution field emission scanning electron microscope, SU8010, manufactured by Hitachi, Japan, was used to observe the micro-morphological characteristics of the sample soot particles. The test conditions were scattering mode, accelerating voltage of 3 kV, working distance of 9.2 mm, and magnification of 20.0 k\u0026times;. Due to the fragile nature of the samples, the sample was embedded with resin before the experiment and pasted on conductive adhesive for observation after curing.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFourier-transform infrared spectroscopy (FTIR).\u003c/b\u003e LUMOS Fourier transform infrared spectrometer (with ATR accessory) manufactured by Bruker, Germany. The number of background scans was 64, the wave number range was 600\u0026thinsp;~\u0026thinsp;4000cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and the resolution was 2cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. During the test, a small piece of sample was taken with tweezers, and an appropriate amount of potassium bromide powder was added, ground until it was mixed well and then pressed into a disc with a metal mold, fixed on the sample stage and loaded into the instrument for testing, and the data were analyzed and graphed using Omnic and Origin software.\u003c/p\u003e \u003cp\u003e \u003cb\u003eThermogravimetric analysis (TGA).\u003c/b\u003e SDT Q600 V20.9 Build 20 Integrated Thermal Analyzer from TA Instruments, USA. For the experiments, 5 mg of fresh samples were taken, ground into powder and loaded into the alumina crucible for thermal analysis, and tested in an air atmosphere with a gas flow rate of 100 ml/min, the starting and stopping temperatures were set from room temperature to 700 ℃, and the heating rate was 5 ℃/min. After exporting the data, the TG curves were plotted with Origin software and analyzed.\u003c/p\u003e \u003cp\u003e \u003cb\u003eEnergy dispersive spectroscopy (EDS).\u003c/b\u003e X-ACT type X-ray spectrometer from Oxford Instrument, UK, equipped with a VEGA-3XMU scanning electron microscope from TESCAN, Czech Republic, was used to analyze the composition of the ash after thermogravimetric analysis of the sample. Appropriate amount of ash powder was pasted on conductive adhesive and tested under 100\u0026times; magnification.\u003c/p\u003e \u003cp\u003e \u003cb\u003eMicro-laser Raman spectroscopy (Raman).\u003c/b\u003e The in Via Qontor micro confocal Raman spectrometer manufactured by Renishaw, UK, is equipped with 532nm, 633nm and 785nm lasers. The experiments were tested with a 532nm laser and the spectral range of the acquisition was 110\u0026thinsp;~\u0026thinsp;1500cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with an objective lens magnification of 50\u0026times;. The Micro-Laser Raman Spectrometer can perform in-situ non-destructive testing at high magnification and realize precise analysis of the sample.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec5\"\u003e\n \u003ch2\u003eScanning electron microscope analysis results\u003c/h2\u003e\n \u003cp\u003eThe samples were resin-embedded before the experiment. The micro-morphological characteristics of the soot particles were observed at 20.0k magnification. And the modern pine-soot ink and modern oil-soot ink produced by Shanghai Ink Factory were selected as the standard samples for this experiment. The micrographs are shown in Fig.\u0026nbsp;2. As can be seen from the figure, the shape of the sample soot particles is nearly spherical, with loose distribution and non-uniform size, and there is the phenomenon of some particles agglomerating and fusing. The size of the sample particles was measured to be around 100 nm on average.\u003c/p\u003e\n \u003cp\u003eAt present, the existing studies have shown that the particles of pine-soot ink have the morphology characteristics of nearly spherical, uneven size, and there is the phenomenon of some particles melting, and the particle diameter distribution is around 100 nm; the particles of oil-soot ink are irregular aggregates, the size of which is more uniform, and the particle size is around 30 nm\u003csup\u003e13,25\u003c/sup\u003e. In terms of particle morphology and size, the sample is closer to the characteristics of pine-soot ink. Therefore, the sample is judged to be pine-soot ink based on the scanning electron micrographs.\u003c/p\u003e\n \u003cp\u003eHowever, more than a thousand years ago, science and technology were not advanced. The ancients needed a high level of craftsmanship to achieve the size of the soot particles in the ink stick to the nanometer level. This is inextricably linked to the process of taking materials, selecting soot and pounding in making ink stick. First of all, the choice of pine wood determines the quality of the soot, during the Eastern Han Dynasty (东汉), Ying shao (应劭) wrote the book called “Han-Guan-Yi (汉官仪)”, which recorded that “The prime minister, the deputy prime minister, the secretary general and the drafter of documents are given one large ink and one small ink from Yu Mi every month (尚书令、仆、丞、郎月赐喻糜大墨一枚、小墨一枚).”\u003csup\u003e26\u003c/sup\u003e. The name “Yu Mi (喻糜)” refers to today's Qianyang (千阳), Shaanxi (陕西) Province, China, which was an important source of fine pine wood at that time. This shows that as late as the Han Dynasty, the ancients already had a clear knowledge of the origin of fine pine wood\u003csup\u003e8\u003c/sup\u003e. Next is the collection of soot, in order to better enrich the soot particles, the firing is usually carried out in a closed soot kiln, which can be categorized into flat kiln and vertical kiln according to the different shapes. Due to the light weight of the soot particles, it will be attached to the kiln wall, and the top soot particles are smaller and lighter, therefore, the “far soot” and “top soot” particles in the kiln are the finest, and the quality of the ink stick made from this kind of soot is the best\u003csup\u003e27\u003c/sup\u003e. In the Ming Dynasty (明), the book “Tian-Gong-Kai-Wu (天工开物)” written by Song Yingxing (宋应星) also recorded that in the process of firing the soot, “the soot located in the last one or two sections is the purest, and is taken as the material for the finest ink stick (靠尾一二节者为清烟, 取入佳墨为料)”\u003csup\u003e28\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eIn addition, pounding is also an important step in the ink stick production process. In ancient times, the production of ink sticks have “add a small amount of glue and pound tens of thousands of times (轻胶万杵)” said, only after repeated pounding, can make the soot particles and animal glue fully combined, the production of ink sticks will be tougher\u003csup\u003e29\u003c/sup\u003e. In the Northern Wei period (北魏时期) (386–534 CE), Jia Sixie (贾思勰) wrote the book “Qi-Min-Yao-Shu (齐民要术)”, which is one of the earliest surviving works on agriculture in China. The book recorded a large number of production methods and techniques, including the “Combined ink method (合墨法)”, mentioned before molding, ink needs to go through the process of “Pounding 30,000 times, the more times more good (捣三万杵, 杵多益善)”\u003csup\u003e30\u003c/sup\u003e. Furthermore, in the “Tian-Gong-Kai-Wu (天工开物)”, Song Yingxing (宋应星) also pointed out that the ink “After adding the animal glue, the number of whacks determines the hardness of the ink stick (和胶之后, 以捶敲多寡分脆坚)”, reflecting the importance of whacks to the ink.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eFourier-transform infrared spectroscopy analysis results\u003c/h3\u003e\n\u003cp\u003eFor the experiment, fresh samples were taken from the inside of the ink stick. Appropriate amount of potassium bromide powder was added for grinding, mixed well and pressed for testing, and the analytical results are shown in Fig.\u0026nbsp;3. The broad peak at 3665 cm\u003csup\u003e− 1\u003c/sup\u003e in the figure represents the stretching vibration of -OH\u003csup\u003e31\u003c/sup\u003e, which may be related to the moisture in the sample; 1778 cm\u003csup\u003e− 1\u003c/sup\u003e assigned to the carbonyl stretching mode of the ester group (vC = O)\u003csup\u003e32\u003c/sup\u003e, indicating the presence of lipid components\u003csup\u003e33\u003c/sup\u003e;1688 cm\u003csup\u003e− 1\u003c/sup\u003e assigned to the C = O stretching vibration of peptide bonds, which can be attributed to the polypeptide chains from ancient proteinaceous materials\u003csup\u003e34\u003c/sup\u003e; and the absorption peak near 1500 cm\u003csup\u003e− 1\u003c/sup\u003e belongs to the C-N-H bending vibration\u003csup\u003e35\u003c/sup\u003e, with the C-N-H being mostly assigned to protein Amide II\u003csup\u003e36\u003c/sup\u003e. Combining the above information, it can be determined that the sample contain animal glue.\u003c/p\u003e\n\u003cp\u003eAnimal glue is an adhesive, the main components of which are gelatin and residues of other proteins collagen, keratin or elastin. It can be made from bones, hides and the intestines of animals (fish, sheep, cattle, horses, etc.). Animal skins and bones are heated with hot water to gather the gelatine in them, cooled and dried to make animal glue\u003csup\u003e37\u003c/sup\u003e. Because of its easy accessibility, convenient processing and low cost, it was a commonly used type of glue by ancient Chinese artisans\u003csup\u003e38\u003c/sup\u003e. Among many animal glues, deer glue, cow glue, fish glue and egg glue were commonly used by ancient Chinese\u003csup\u003e39\u003c/sup\u003e. And depending on the actual situation, the ancients also mixed many kinds of animal glues\u003csup\u003e40\u003c/sup\u003e. Due to the cracking and peeling of the sample surface, the organic matter in the ink stick will be partially lost, so the infrared spectra of the sample is not very typical, but the above infrared characteristic peaks can be used as a basis for judging that the sample contains organic binding medium.\u003c/p\u003e\n\u003cp\u003eGlue also plays a very important role in the production of ink sticks. Chao Jiyi (晁季一), a scholar of the Song Dynasty, once wrote in his book “Mo-Jing (墨经)” that “For all ink sticks, glue is the most important. If you have the best soot but the glue method is not appropriate, the ink sticks will not be good. If you get the right glue method, even if you don't have that good soot, you can make good ink sticks (凡墨, 胶为大。有上等煤而胶不如法, 墨亦不佳。如得胶法, 虽次煤能成善墨)”\u003csup\u003e41\u003c/sup\u003e. The addition of animal glue can not only coagulate the soot particles into a solid form of ink stick, which plays a role in molding, but also make the ink stick not easy to appear particles precipitation after grinding with water, which is convenient for writing. In addition, it can also enhance the bond between ink and paper, which is not easy to fall off after writing, and is conducive to the long-term preservation of calligraphy and painting works\u003csup\u003e27\u003c/sup\u003e. The infrared spectral analysis confirms that animal glue was added to the sample during the production process, which is an important reason why the ancient ink sticks retained their original form after being buried in tombs for more than a thousand years.\u003c/p\u003e\n\u003ch3\u003eThermogravimetric analysis results\u003c/h3\u003e\n\u003cp\u003eThe ink sticks are mainly composed of soot and glue, which have large differences in thermal decomposition and weight loss temperatures. Therefore thermogravimetric analysis can reflect their compositional specific gravity\u003csup\u003e42\u003c/sup\u003e. For the experiment, 5 mg of uncontaminated sample inside the ink stick was selected and ground into powder to test the thermal decomposition and weight loss process of the sample under air atmosphere. According to the variation of the thermogravimetric curve, the weight loss process of the sample is roughly divided into three stages: ⅰ) loss of water; ⅱ) thermal cracking of molecules such as glue material; ⅲ) oxidative combustion of carbon particles\u003csup\u003e18\u003c/sup\u003e. The results of thermogravimetric analysis are shown in Fig.\u0026nbsp;4.\u003c/p\u003e\n\u003cp\u003eBy calculating the weight percentages of the glue stage and the soot stage, the glue to soot ratio in the sample was estimated to be 0.16 (glue/soot = 10%/63% ≈ 0.16.). Based on ink-making monographs from the Northern Song Dynasty, such as the “Mo-Jing (墨经)”, the “Wen-Fang-Si-Pu (文房四谱)” and the “Mo-Pu-Fa-Shi (墨谱法式)”. These books recorded the methods and steps of the ancient method of ink production, and also mentioned the amount of glue and soot material many times. The proportion of glue used in different ancient ink-making methods is detailed in Table\u0026nbsp;1. Ancient Chinese weight units continued the weights and measures system of the Qin Dynasty (秦), with one catty (斤) being about sixteen taels (两), which can be converted to the glue to soot ratio of about 0.3 recorded in these monographs. In comparison, the proportion of glue to soot in the sample was significantly lower, which may be related to the gradual aging and loss of organic glue caused by the long burial time of the ink stick.\u003c/p\u003e\n\u003cdiv\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 1\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eัGlue to soot ratios of different methods of making ink sticks in ancient China\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"6\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMonograph\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAuthor\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMethod\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDosage\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eGlue/Soot\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRatio\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e“Mo-Jing”\u003c/p\u003e\n \u003cp\u003e(墨经)\u003csup\u003e41\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChao Jiyi\u003c/p\u003e\n \u003cp\u003e(晁季一)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eJia Sixie’s Method\u003c/p\u003e\n \u003cp\u003e(贾思勰墨法)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e“One catty of soot, five taels of glue”\u003c/p\u003e\n \u003cp\u003e(煤一斤, 用胶五两)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5/16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.31\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e“Wen-Fang-Si-Pu”\u003c/p\u003e\n \u003cp\u003e(文房四谱)\u003csup\u003e43\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSu Yijian\u003c/p\u003e\n \u003cp\u003e(苏易简)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWei Zhongjiang’s Method\u003c/p\u003e\n \u003cp\u003e(韦仲将墨法)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e“One catty of fine soot, five taels of good glue”\u003c/p\u003e\n \u003cp\u003e(烟一斤以上, 好胶五两)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5/16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.31\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"4\"\u003e\n \u003cp\u003e“Mo-Pu-Fa-Shi”\u003c/p\u003e\n \u003cp\u003e(墨谱法式)\u003csup\u003e44\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"4\"\u003e\n \u003cp\u003eLi Xiaomei\u003c/p\u003e\n \u003cp\u003e(李孝美)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eAncient Method\u003c/p\u003e\n \u003cp\u003e(古墨墨法)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e“Six taels of glue, one catty of soot”\u003c/p\u003e\n \u003cp\u003e(胶六两, 煤一斤)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6/16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.38\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e“Five taels of antler gelatin, one catty of coal”\u003c/p\u003e\n \u003cp\u003e(鹿角胶五两, 煤一斤)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5/16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.31\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eOil-soot ink Method\u003c/p\u003e\n \u003cp\u003e(油烟墨墨法)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e“Four taels of glue, one catty of soot”\u003c/p\u003e\n \u003cp\u003e(胶四两, 煤一斤)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4/16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e“Five taels of rubber, one catty of coal”\u003c/p\u003e\n \u003cp\u003e(胶五两, 煤一斤)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5/16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.31\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\"\u003e\n \u003ch2\u003eEnergy dispersive spectroscopy analysis results\u003c/h2\u003e\n \u003cp\u003eIt can be observed from Fig.\u0026nbsp;4 that the sample still has about 17% residue at the end of thermogravimetric analysis. The residual weight in the sample is related to the impurities in the ink stick that are not easily combustible, since moisture, glue and soot can all be decomposed when heated in an air atmosphere\u003csup\u003e18\u003c/sup\u003e. The ancients would have added other additives to the ink-making process, and the study used energy dispersive spectroscopy to analyze the composition of the residual ash. At the same time, the original composition of the ink stick sample without thermogravimetric analysis was also analyzed, and the results can be used as a comparison of the ash elemental data, and the two corroborate each other, so as to fully reveal the elements other than C, H and N in the ink stick, and further excavating the information on the production process of the pine-soot ink in the Northern Song Dynasty.\u003c/p\u003e\n \u003cp\u003eTake the appropriate amount of ash powder and ink stick internal sample pasted on the conductive adhesive, magnification 100×. Before the test, ash and ink stick were not sprayed with gold and carbon, elemental data are normalized, the results are detailed in Table\u0026nbsp;2, the specific test points are shown in Fig.\u0026nbsp;5.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 2\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eัThe EDS analysis results of ash and ink stick (Wt/%)\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"11\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003eAsh\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003eInk stick\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eElement\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e53.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e77.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e79.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e79.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e79.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e46.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e41.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e43.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e42.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e44.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCl\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e31.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.58\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFe\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCu\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.22\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe results show that the composition of the ash is mainly Ca element and O element, which was related to the fact that a certain amount of CaCO\u003csub\u003e3\u003c/sub\u003e was added to the ink stick during the preparation process, which was transformed into CaO after high-temperature decomposition\u003csup\u003e18\u003c/sup\u003e. In addition, a certain amount of carbon is present in the ash. During the heating process, limited by the reaction rate, element C may not be completely oxidized to CO\u003csub\u003e2\u003c/sub\u003e at high temperatures, so a certain amount of element C remains\u003csup\u003e18\u003c/sup\u003e. The higher content of element Pb reflects the information about the sample making process. The presence of Cu element may be related to the metal burials in the tombs, but there are also related studies that show that Cu can play a role in increasing the color in the ancient ink\u003csup\u003e12\u003c/sup\u003e. The ash also includes trace amounts of Si, Al, and Mg, which are also found in the ink stick and are caused by contact with the soil in the burial. In addition, very trace amounts of the Cl element were detected in the ink stick, presumably the samples were affected by soluble salts in the burial environment.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eMicroscopic laser Raman spectroscopy analysis results\u003c/h3\u003e\n\u003cp\u003eTo further explore the information about the additives in the sample, the study utilized microscopic laser Raman spectroscopy to analyze the ash as well as the ink stick for the first time. The experiment was conducted by taking appropriate amounts of ash powder and uncontaminated samples inside the ink stick under a 50× objective lens, and it was seen that there were obvious white particles and yellow particles in both the ash and the ink stick. These particles have regular shapes, clear boundaries, and uniform colors. Combined with the fact that ancient craftsmen often added other additives to the ink sticks, the study suggests that these particles were added artificially after grinding, which could reflect information on the process of making pine-soot ink. The test was performed with a 532nm laser, the test points and results are shown below. After analysis, the gray-white particles in the ash and ink stick are limestone (CaCO\u003csub\u003e3\u003c/sub\u003e), the yellow particles are lithargite (PbO) and the silver-white particles are jarosite (KFe\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e3+\u003c/sup\u003e(OH)\u003csub\u003e6\u003c/sub\u003e(SO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e). The analytical results correspond exactly to the elemental data.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLimestone (CaCO\u003c/strong\u003e \u003csub\u003e\u0026nbsp;\u003cstrong\u003e3\u003c/strong\u003e\u0026nbsp;\u003c/sub\u003e \u003cstrong\u003e).\u003c/strong\u003e Raman results show that the gray-white particles in the ash have obvious peak at 1086 cm\u003csup\u003e− 1\u003c/sup\u003e; those of the ink stick also have peaks at 152 cm\u003csup\u003e− 1\u003c/sup\u003e, 277 cm\u003csup\u003e− 1\u003c/sup\u003e, 713 cm\u003csup\u003e− 1\u003c/sup\u003e and 1086 cm\u003csup\u003e− 1\u003c/sup\u003e, which are characteristic peaks of limestone (CaCO\u003csub\u003e3\u003c/sub\u003e), as shown in Fig. 6. According to ancient ink-making monographs, the production of ancient ink sticks included the following steps: “selecting materials (选材), obtaining soot (取烟), sieving (罗筛), adding glue (和胶), adding medicine (入药), steaming (蒸剂), pounding (杵捣), rolling into balls (擀丸), molding (制样) and shade-drying (荫干)”\u003csup\u003e45\u003c/sup\u003e. Among them, the lime used for shade drying is the main reason for the presence of calcium carbonate in the ink stick.\u003c/p\u003e\n\u003cp\u003eIn the process of making ink sticks, due to the water added to the decoction of glue, in order to avoid deformation and cracking in the drying process of the ink stick has been molded, the ancient craftsmen in the addition of glue will intentionally control the humidity of the ink, “rather dry than wet (宁干勿湿)”\u003csup\u003e44\u003c/sup\u003e. And will be put the ink stick into furnace ash, lime or wheat bran, these substances have hygroscopicity, the ancients took advantage of this property so that the ink sticks can slowly shade dry\u003csup\u003e41\u003c/sup\u003e, this step was also called “put into the ash (入灰)”. In the Ming Dynasty (明), “Fang-Shi-Mo-Pu (方氏墨谱)” also recorded that the ink stick “is put into the ash to remove the smell of glue, and has a beneficial effect on the color of the ink stick (纳之灰中能去胶气而益墨色)”, “dries easily in the ash without cracking (置灰中易干而不溃)”\u003csup\u003e46\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eAfter the ink stick was put into the ash, “it must not be exposed to the wind or it will break (不可见风, 见风墨断)”, the whole shade drying process needs to be carried out in a closed and windless environment. Then, after a period of time, “Through the ink sticks hit each other, if the sound is crisp and loud, it can be taken out of the ash (以墨相击, 其声干响, 方可出灰)”, and then use a brush to clean up the ash on the ink stick\u003csup\u003e45\u003c/sup\u003e. Accordingly, it can be inferred that the sample also went through the step of “put into the ash (入灰)”, and was shade-dried with lime. In the process of shade drying, due to the closed environment without wind, the lime powder will gradually penetrate into the ink stick, which leads to the presence of a high content of Ca and O elements in the sample.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLithargite (PbO).\u003c/strong\u003e The study utilized microscopic laser Raman spectroscopy to analyze the yellow particles in the ash and ink stick, and the results are shown in Fig. 7. The results show that the main peaks of the yellow particles are all located near 145 cm\u003csup\u003e− 1\u003c/sup\u003e, indicating that their main component is lead oxide (PbO)\u003csup\u003e47\u003c/sup\u003e, which is also known as “lithargite (密陀僧)”. In addition, the yellow particles in the ash also show peaks at 200 cm\u003csup\u003e− 1\u003c/sup\u003e, 290 cm\u003csup\u003e− 1\u003c/sup\u003e, 397 cm\u003csup\u003e− 1\u003c/sup\u003e, 508 cm\u003csup\u003e− 1\u003c/sup\u003e and 635 cm\u003csup\u003e− 1\u003c/sup\u003e corresponding to lead dioxide (PbO\u003csub\u003e2\u003c/sub\u003e)\u003csup\u003e48\u003c/sup\u003e. This is due to the fact that the thermogravimetric analysis was carried out in an air atmosphere and the lead oxide particles in the ink stick were gradually oxidized to lead dioxide during the slow heating process.\u003c/p\u003e\n\u003cp\u003eLead was one of the first few metals recognized by mankind, and in the process of smelting lead, the ancient Chinese smelted artificial compounds of lead such as lead tetroxide (铅丹) and lithargite (密陀僧)\u003csup\u003e49\u003c/sup\u003e. Lithargite is lead oxide (PbO), because its color is generally yellow, so it is also known as “lead yellow (铅黄)”, in cultural relics are mainly used as yellow pigments\u003csup\u003e50\u003c/sup\u003e. The famous Tang Dynasty(唐) medical book “Xin-Xiu-Ben-Cao (新修本草)” recorded the source of lithargite in ancient China, and believed that before the Tang Dynasty, lithargite “came from the country of Persia (来自波斯国)”\u003csup\u003e51\u003c/sup\u003e. However, archaeological data show that as early as the Qin Dynasty (秦), ancient Chinese were able to synthesize lead oxide artificially and used it as pigment to paint the surface of terracotta figurines\u003csup\u003e52\u003c/sup\u003e. By the Tang Dynasty (唐), the use of lithargite as a color pigment had become very common\u003csup\u003e49\u003c/sup\u003e. Therefore, it is no coincidence that lithargite appears in the ink stick of the Song Dynasty (宋).\u003c/p\u003e\n\u003cp\u003eThe “Xin-Xiu-Ben-Cao (新修本草)” also recorded that lithargite had insecticidal and fungistatic properties, and that it could be used in medicine to “treat sores and subdue swellings and poisons”\u003csup\u003e51\u003c/sup\u003e. In ancient times, in order to further improve the performance of ink sticks, craftsmen would add medicinal herbs and spices, which was called “adding medicine (入药)”. For example, the addition of borneol (龙脑) and musk (麝香) can increase the aroma of ink stick; the addition of gleditsia sinensis (皂角) can help remove moisture and the addition of dioscorea bulbifera (黄药) can make the ink stick grinding soundless\u003csup\u003e46\u003c/sup\u003e. Among them, borneol is also called “bing piàn (冰片)”, which was documented in the “Ben-Cao-Gang-Mu (本草纲目)” as having antimicrobial properties. In 2011, Shuya Wei et al. detected it in ink stick excavated from Leitiao (雷鋽) tomb in the Eastern Jin Dynasty (东晋) using pyrolysis gas chromatography and mass spectrometry (Py-GC/MS) and concluded that it was added to prevent biological attack\u003csup\u003e53\u003c/sup\u003e. Therefore, the addition of lithargite, which also has an insecticidal effect, to the ink stick was also to prevent the ink stick from being attacked by organisms and to facilitate its long-term preservation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eJarosite (KFe\u003c/strong\u003e \u003csub\u003e\u0026nbsp;\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u0026nbsp;\u003cstrong\u003e3+\u003c/strong\u003e\u0026nbsp;\u003c/sup\u003e \u003cstrong\u003e(OH)\u003c/strong\u003e\u003csub\u003e\u0026nbsp;\u003cstrong\u003e6\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e(SO\u003c/strong\u003e\u003csub\u003e\u0026nbsp;\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e)\u003c/strong\u003e\u003csub\u003e\u0026nbsp;\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e).\u003c/strong\u003e The silver-white particles in the ash and ink stick were analyzed to be jarosite\u003csup\u003e54\u003c/sup\u003e. The Raman peak positions are shifted to some extent due to environmental factors\u003csup\u003e55\u003c/sup\u003e, but the overall trend of the spectra are the same and correspond to the elemental data. And due to the presence of organic matter in the ink stick, the Raman signal was interfered by fluorescence to a certain extent, and only the main peaks 210 cm\u003csup\u003e− 1\u003c/sup\u003e and 460 cm\u003csup\u003e− 1\u003c/sup\u003e of jarosite with stronger signals are detected in the ink stick\u003csup\u003e56\u003c/sup\u003e. The Raman results are shown in Fig. 8.\u003c/p\u003e\n\u003cp\u003eJarosite is a member of the alum group with the chemical formula KFe\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e3+\u003c/sup\u003e(OH)\u003csub\u003e6\u003c/sub\u003e(SO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, which is a product of the oxidation of pyrite. It was once discovered during the mining of silver, gold and lead ores\u003csup\u003e57\u003c/sup\u003e and has been used in metallurgical and environmental fields due to its strong adsorption capacity\u003csup\u003e58,59\u003c/sup\u003e. However, the natural sources of jarosite are relatively limited, and most of the jarosite used for research is synthesized under laboratory conditions, which are mostly different from those in nature, resulting in the fact that the crystal structures of the synthesized minerals and the natural minerals may be the same, but the molecular structures may not be the same. Therefore, the spectra of the synthesized minerals are not necessarily the same as those of the natural minerals\u003csup\u003e56\u003c/sup\u003e, which is the main reason for the shift in the peak position of the jarosite in the sample.\u003c/p\u003e\n\u003cp\u003eIn cultural relics, jarosite can be used as a yellow pigment\u003csup\u003e60,61\u003c/sup\u003e, but it is not common, so there are fewer studies on jarosite in cultural relics, and the existing analytical work is more focused on foreign countries. The detection of jarosite in the sample not only provides new data for the study of ancient Chinese ink sticks, but also complements the study of jarosite in the field of cultural relics.\u003c/p\u003e\n\u003cp\u003eThe main component of pyrite is iron sulfide (FeS\u003csub\u003e2\u003c/sub\u003e), which is easily oxidized slowly in acidic and anoxic environments to produce jarosite\u003csup\u003e62,63\u003c/sup\u003e, which coincides with the burial environment of the sample, so the presence of jarosite suggests that pyrite may have been added to the sample at the beginning of its production, and then slowly oxidized to jarosite in the prolonged burial environment. Pyrite has a similar appearance to gold, and many people would mistake pyrite for gold, commonly known as “fool's gold (愚人金)”\u003csup\u003e64\u003c/sup\u003e. In order to increase the luster of the ink sticks, ancient craftsmen also added substances such as cinnabar and gold foil during the ink-making process\u003csup\u003e45\u003c/sup\u003e. The ancient Chinese craftsmen chose pyrite, which is very similar in appearance to gold but costs much less than gold, indicates that by the Song Dynasty, craftsmen not only mastered the process of making ink sticks, but also could reduce the production cost by adjusting the type of material used to make them, further proving that the ink-making craftsmen of the Song Dynasty already possessed a high level of technology.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eBased on the scanning electron microscope results, it can be determined that the sample is pine-soot ink. And animal glue was detected in the sample using fourier transform infrared spectroscopy. Since the weight loss stage of the sample is distinct in the air atmosphere, by calculating the weight percentage of the glue stage and the soot stage, it can be concluded that the glue to soot ratio of the sample is 0.16, which is lower than that of the ratio of 0.3 recorded in the ancient books, and it is presumed that aging and partial loss of the glue in the sample occurred in the long term burial process. To further explore the production process, the composition of the ash and ink stick was analyzed using energy dispersive spectroscopy and microscopic laser raman spectroscopy, which detected lime for shade drying (CaCO\u003csub\u003e3\u003c/sub\u003e), lithargite with insecticidal properties (PbO) and jarosite, an oxidized product of pyrite that can increase the luster of the ink stick (KFe\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e3+\u003c/sup\u003e(OH)\u003csub\u003e6\u003c/sub\u003e(SO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e). The above information fully reveals the craftsmanship of the Northern Song Dynasty pine-soot ink from multiple angles, proving that craftsmen of this period not only mastered the ink-making process, but also were able to reduce production costs by adjusting the types of materials. This sample exemplifies the development of the Song dynasty's pine-soot ink production process to its peak. The study is the first time to conduct scientific and technical analysis on the ash content of the ink stick after thermogravimetry, and dig deeper into the information of inorganic components. It corroborates and supplements the records on ink in ancient literature, provides new data for the study of the production process of pine-soot ink, and enriches the study of the ancient Chinese ink-making process, thus promoting the continuation and development of the traditional Chinese craftsmanship.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThanks to Shaanxi Academy of Archaeology for providing the sample. This work has been supported by the National Natural Science Foundation of China (NO. 22101226), 111 project (D18004).\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDaishi Qi performed all experimental tests, interpreted the data, and wrote the manuscript. Feng Sun provided support and guidance for this study. Xuwei Chen provided the sample used in the study. All authors read and approved the final version.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCompeting interests \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrespondence\u003c/strong\u003e and requests for materials should be addressed to Feng Sun.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eReprints and permissions information\u003c/strong\u003e is available at \u003c/p\u003e\n\u003cp\u003ehttp://www.nature.com/reprints \u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003ePublisher\u0026rsquo;s note\u003c/strong\u003e Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.\u003c/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eOpen Access\u003c/strong\u003e This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article\u0026rsquo;s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article\u0026rsquo;s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.\u003c/p\u003e\n\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eRasmussen, K.L. et al. The constituents of the ink from a Qumran inkwell: new prospects for provenancing the ink on the Dead Sea Scrolls. \u003cem\u003eJ. Archaeol. 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Eng.\u003c/em\u003e\u003cstrong\u003e25\u003c/strong\u003e, 88. https://link.cnki.net/doi/10.16536/j.cnki.issn.1671-1211.2011.01.024 (2011) (in Chinese).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"npj-heritage-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"hsci","sideBox":"Learn more about [Heritage Science](http://heritagesciencejournal.springeropen.com)","snPcode":"40494","submissionUrl":"https://submission.nature.com/new-submission/40494/3","title":"npj Heritage Science","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6364938/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6364938/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"This study is based on the ink stick unearthed from the tombs of the Northern Song Dynasty (960 CE-1127 CE) in Xi 'an, Shaanxi Province, during which the development of ancient Chinese ink making technology reached its peak. The sample was analyzed by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), energy dispersive analysis (EDS) and microscopic laser Raman spectroscopy (Raman). The sample was identified as pine-soot ink, and animal glue was added in the production process. In addition, lime (CaCO3) for shade drying, lithargite (PbO) for insecticidal effect and jarosite (KFe33+(OH)6(SO4)2), the oxidation product of pyrite (FeS), which is similar to gold in appearance but lower in cost, were also detected in ash and ink stick, fully revealing the production process of pine-soot ink in Song Dynasty.","manuscriptTitle":"Scientific and technological analysis and research on the ink stick unearthed from the tomb of Fanxiaochong of the Northern Song Dynasty in Xi'an, Shaanxi Province","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-24 14:31:31","doi":"10.21203/rs.3.rs-6364938/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-05-25T16:05:42+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-22T09:40:04+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-16T07:32:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-05-14T03:22:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"76849974382519667444684951013703325206","date":"2025-05-06T07:09:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"693441597202331324641363216310195224","date":"2025-05-05T18:30:14+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-04-24T14:31:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"210115888249924567848218469825949066408","date":"2025-04-23T00:48:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"85906117979057349079308824001701651884","date":"2025-04-03T23:29:50+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-03T15:32:09+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-03T06:19:22+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-03T06:16:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"npj heritage science","date":"2025-04-03T01:44:24+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"npj-heritage-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"hsci","sideBox":"Learn more about [Heritage Science](http://heritagesciencejournal.springeropen.com)","snPcode":"40494","submissionUrl":"https://submission.nature.com/new-submission/40494/3","title":"npj Heritage Science","twitterHandle":"@SpringerOpen","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"526fc4cf-12e3-49c7-83df-3432845f16da","owner":[],"postedDate":"April 24th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-08-18T16:02:30+00:00","versionOfRecord":{"articleIdentity":"rs-6364938","link":"https://doi.org/10.1038/s40494-025-01976-5","journal":{"identity":"npj-heritage-science","isVorOnly":false,"title":"npj Heritage Science"},"publishedOn":"2025-08-13 15:57:46","publishedOnDateReadable":"August 13th, 2025"},"versionCreatedAt":"2025-04-24 14:31:31","video":"","vorDoi":"10.1038/s40494-025-01976-5","vorDoiUrl":"https://doi.org/10.1038/s40494-025-01976-5","workflowStages":[]},"version":"v1","identity":"rs-6364938","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6364938","identity":"rs-6364938","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}