Synchrotron small-angle X-ray scattering: a non-destructive technique for identifying vegetable tanned leather cultural relics

Abstract

Abstract

Leather cultural relics are valuable materials for reconstructing and understanding human civilization. However, identifying the tanning agents used in their manufacture remains challenging due to the absence of rapid, non-destructive analytical techniques. This work presents a pioneering non-destructive approach, based on synchrotron small-angle X-ray scattering (SAXS), for identifying vegetable tanned ancient leathers. To validate the method, six simulated ancient leather samples (produced by vegetable, oil, smoke, aluminum, iron, and mirabilite-flour tanning) were analyzed using SAXS, in combination with attenuated total reflectance Fourier transform infrared spectroscopy, X-ray fluorescence, and pyrolysis–gas chromatography-mass spectrometry. SAXS analysis revealed distinctive diffraction patterns: vegetable tanned leathers exhibited minimal or absent peaks due to masking of the collagen fibril D-periodic structure by vegetable tannins, whereas non-vegetable tanned leathers displayed clear periodic diffraction peaks. Application of this method to seven cultural relic samples identified two as vegetable tanned leathers, a result further corroborated by phenolic pyrolysis products detected via pyrolysis–gas chromatography-mass spectrometry. This SAXS-based strategy enables rapid and non-destructive identification of vegetable tanned leather cultural relics.

Graphical Abstract

Keywords

SAXS / Vegetable tanned leather / Non-destructive / Cultural relic / Collagen fibril

References

[1] Rusbridge TBS. The culture of materials and leather objects in eighteenth-century England. 2020, Birmingham, University of Birmingham

[2] Doyon L, Faure T, Sanz M, Daura J, Cassard L, d’Errico F. A 39,600-year-old leather punch board from Canyars, Gavà, Spain. Sci Adv. 2023, 9(15): 0834.

[3] Zhang MR, Hu YD, Liu J, Pei Y, Tang KY, Lei Y. Biodeterioration of collagen-based cultural relics: a review. Fungal Biol Rev. 2022, 39: 46-59.

[4] Hu YD, Liu J, Han GH, Li XM, Zhang ZH, Zheng XJ, Wang F, Pei Y, Lei Y, Tang KY. Artificial deterioration of vegetable-tanned tanned leather under synergistic effect of temperature and humidity. J Cult Herit. 2022, 53: 118-126.

[5] Wang YN, Zhang YX, Wang Z. Biodegradability of leather: a crucial indicator to evaluate sustainability of leather. Collagen Leather. 2024, 61. 12

[6] Xue PB, Yu Y, Wang H, Cao YL, Shi B, Wang YN. Oxidized sodium lignosulfonate: a biobased chrome-free tanning agent for sustainable eco-leather manufacture. Ind Crop Prod. 2024, 208. 117916

[7] Yu Y, Wang H, Wang YN, Zhou JF, Shi B. Chrome-free synergistic tanning system based on biomass-derived hydroxycarboxylic acid–zirconium complexes. J Clean Prod. 2022, 336. 130428

[8] Yao SL, Yang HL, Li HY, Yu Y, Wang YN, Zhou Y, Shi B, Zeng YH. Deterioration characteristics of various simulated samples of ancient tanned leathers: a comparative study. J Am Leather Chem Assoc. 2025, 120: 373-383

[9] Yao SL, Lin YR, Lei C, Wang YN, Yu Y, Zeng YH. Comparison of various test methods to quantify the deterioration degree of archaeological leather. Herit Sci. 2024, 1201. 320

[10] Falcao L, Araújo MEM. Application of ATR-FTIR spectroscopy to the analysis of tannins in historic leathers: the case study of the upholstery from the 19th century Portuguese Royal Train. Vib Spectrosc. 2014, 74: 98-103.

[11] Rahme L. Fish skin, a sustainable material used from ancient times to today's fashion. FormAkademisk. 2021, 1421-16.

[12] Thomson RS. Tanning-man’s first manufacturing process?. Trans Newcomen Soc. 1981, 53(1): 139-156.

[13] Yuan HM. Overview of the historical development of Yunnan leather craft. J Beijing Inst Graph Commun. 2021, 29(4): 94-96.

[14] Mercuri F, Cicero C, Dadi L, Gottscher C, Paoloni S, Zammit U, Migliore L, Orazi N. Stability and durability assessment of alum-tawed skin by light transmission analysis. J Cult Herit. 2024, 67: 534-540.

[15] Luo WG, Si Y, Wang HM, Qin Y, Huang FC, Wang CS. Leather material found on a 6th BC Chinese bronze sword: a technical study. Spectrochim Acta A Mol Biomol Spectrosc. 2011, 79(5): 1630-1633.

[16] Falcao L, Araújo MEM. Vegetable tannins used in the manufacture of historic leathers. Molecules. 2018, 23(5): 1080.

[17] Kite M, Thomson R. Conservation of leather and related materials. 2006, London, Routledge58

[18] Falcao L, Araújo MEM. Tannins characterisation in new and historic vegetable tanned leathers fibres by spot tests. J Cult Herit. 2011, 122149-156.

[19] Nikolova D, Goshey I. Modification of the method of: Broadhurst and·Jones for proving of tannins in cultural-historical objects. Cr Acad Bulg Sci. 2009, 62(7): 825-830

[20] Koochakzaei A, Sabaghian M. Tannin characterization and sourcing in historical leathers through FTIR spectroscopy and PCA analysis. Collagen Leather. 2023, 5(1): 21.

[21] Falcao L, Araújo MEM. Tannins characterization in historic leathers by complementary analytical techniques ATR-FTIR, UV-Vis and chemical tests. J Cult Herit. 2013, 146499-508.

[22] Conca S, Gatto V, Samiolo R, Giovando S, Cassani A, Tarabra E, Beghetto V. Characterisation and tanning effects of purified chestnut and sulfited quebracho extracts. Collagen Leather. 2024, 6(1): 28.

[23] Yang XH, Liu YZ, Liu ZZ, Liu JX, Song JH, Zhou Y, Cui YL. Compositional analysis of archaeological leather and simulated leather and their degradation research based on HRMS. Anal Methods-UK. 2025, 17: 6190-6198.

[24] Sebestyén Z, Czégény Z, Badea E, Carsote C, Sendrea C, Barta-Rajnai E, Bozi J, Miu L, Jakab E. Thermal characterization of new, artificially aged and historical leather and parchment. J Anal Appl Pyrol. 2015, 115: 419-427.

[25] Zhang Y, Mansel BW, Naffa R, Cheong S, Yao Y, Holmes G, Chen HL, Prabakar S. Revealing molecular level indicators of collagen stability: minimizing chrome usage in leather processing. ACS Sustainable Chem Eng. 2018, 657096-7104.

[26] Li RB, Yang C, Liu YQ, Yu Y. A novel approach for analyzing the migration behavior of fatliquors within leather. Collagen Leather. 2025, 7: 8.

[27] Zhou YX, Yu Y, Wang H, Shi B, Wang YN. Green salt-free high-exhaustion chrome tanning strategy: biomass-derived aldehyde acid-chrome tanning. Ind Eng Chem Res. 2025, 64(1): 71-80.

[28] Zhang Y, Ingham B, Cheong S, Ariotto N, Tilley RD, Naffa R, Holmes G, Clarke DJ, Prabakar S. Real-time synchrotron small-angle X-ray scattering studies of collagen structure during leather processing. Ind Eng Chem Res. 2018, 57163-69.

[29] Yu Y, Wang H, Zeng YH, Zhou JF, Zhang Y, Shi B, Wang YN. Biomass-derived polycarboxylate–aluminum–zirconium complex tanning system: a sustainable and practical approach for chrome-free eco-leather manufacturing. J Clean Prod. 2024, 452. 142261

[30] Kayed HR, Sizeland KH, Wells HC, Kirby N, Hawley A, Mudie S, Haverkamp RG. Age differences with glutaraldehyde treatment in collagen fibril orientation of bovine pericardium. J Biomater Tissue Eng. 2016, 6(12): 992-997.

[31] Yi YD, Zhang Y, Mansel B, Wang YN, Prabakar S. Effect of dialdehyde carboxymethyl cellulose cross-linking on the porous structure of the collagen matrix. Biomacromol. 2022, 23(4): 1723-1732.

[32] Sizeland KH, Wells HC, Edmonds RL, Kirby N, Haverkamp RG. Effect of tanning agents on collagen structure and response to strain in leather. J Am Leather Chem As. 2016, 111(11): 391-397

[33] Li HY, Wang H, Yu Y, Yang HL, Zhou Y, Yang RL, Wang YN. Tanning process restoration and simulated sample development of ancient leather. Leather Sci Eng.. 2025, 35(1): 34-41.

[34] Liu JL, Dai L, Xu YL, Wang HB, Xu CZ, Wei BM. Effects of cryo-grinding pretreatment on molecular structure and properties of collagen. Fine Chem.. 2023, 40(11): 2386-2393.

[35] Sebestyén Z, Jakab E, Badea E, Barta-Rajnai E, Sendrea C, Czégény Z. Thermal degradation study of vegetable tannins and vegetable tanned leathers. J Anal Appl Pyrol. 2019, 138: 178-187.

[36] Kanwal N, Musharraf SG. Analytical approaches for the determination of adulterated animal fats and vegetable oils in food and non-food samples. Food Chem. 2024, 460. 140786

[37] Zhang ZT, Liu Y, Wang JC, Xie TL, Sun LY, Li ZJ. A chrome-free combination tanning strategy: based on silicic acid and plant tannin. J Leather Sci Eng. 2021, 15: 3.

[38] Grigsby WJ. Photooxidative stability provided by condensed tannin additives in acrylic-based surface coatings on exterior exposure. J Coat Technol Res. 2018, 1561273-1282.

[39] La Nasa J, Biale G, Sabatini F, Degano I, Colombini MP, Modugno F. Synthetic materials in art: a new comprehensive approach for the characterization of multi-material artworks by analytical pyrolysis. Herit Sci. 2019, 7: 8.

[40] Pascual-Cosp J, Artiaga R, Corpas-Iglesias F, Benítez-Guerrero M. Synthesis and characterization of a new aluminium-based compound. Dalton T. 2009, 326299-6308.

[41] Sebestyén Z, Badea E, Carsote C, Czégény Z, Szabó T, Babinszki B, Bozi J, Jakab E. Characterization of historical leather bookbindings by various thermal methods (TG/MS, Py-GC/MS, and micro-DSC) and FTIR-ATR spectroscopy. J Anal Appl Pyrol. 2022, 162. 105428

Funding

the National Key R&D Program(2022YFF0904100)

the Fundamental Research Funds for the Central Universities

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The Author(s)