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Abstract This article presents a thorough overview of gel-based cleaning methods used in art conservation. It covers the evolution of traditional approaches and the development of advanced gel systems. The paper examines the structure, characterization, and classification of gels, as well as their mechanical properties, which are crucial in art conservation. Various types of gels, including hydrogels, organogels, xerogels, semi-IPNs, and microgels, are discussed in detail, highlighting their unique properties and suitability for specific conservation applications. The advantages, limitations, and applications of both natural and synthesized polymers that form the basis for these gels are also analyzed. Case studies are presented to demonstrate the practicality and effectiveness of gels in cleaning different materials such as paper, paintings, metals, and textiles. These case studies showcase successful removal of stains, pollutants, and unwanted layers while preserving the integrity and aesthetic value of the artworks. By contributing to the existing knowledge on gel-based cleaning approaches in art conservation, this comprehensive review establishes a foundation for future research and development in this field. The review concludes with a discussion on the challenges and potential future directions in the development and optimization of gel-based cleaning methods for art conservation. Overall, this article is a valuable resource for researchers, conservators, and students in the field of art conservation, providing essential information and insights into the use of gels as effective and safe cleaning agents.

This research presents a comprehensive study on the application of hydroxypropyl cellulose/zinc oxide nanocomposite (HPC/ZnO NC) as an effective consolidant in leather conservation. The critical focus is to prevent photooxidative degradation, a significant challenge in preserving historical leather artifacts. The nanocomposite was evaluated for its protective capabilities against environmental stressors like UV radiation and moisture, mechanical robustness, and potential to stabilize acid-damaged leather. The uniform dispersion of ZnO NPs in the HPC matrix was revealed as crucial for improving leather properties, which was confirmed through SEM imaging. The HPC/ZnO NC coating effectively prevented UV-induced microcracks, surface degradation and collagen denaturation. It also demonstrated enhanced mechanical resistance, inhibiting the reduction in leather’s maximum tolerable force and increasing the elongation index, even after aging. Additionally, it exhibited improved water-repellent properties and increased the pH of the leather, offering potential benefits for the treatment of acid-degraded leathers. Overall, the findings affirm that the application of HPC/ZnO NC significantly augments the physical and mechanical properties of leather, providing enhanced resistance to environmental degradation.

Abstract In recent years, the expansion of non-invasive methods has been a trend in identifying historical pigments. Accordingly, this study aimed to identify the pigments used in three Iranian historical manuscripts from the Qajar era by utilizing a non-invasive and multi-analytical approach. A combination of various multi-band imaging methods, along with µ-XRF, Raman and FORS spectroscopy, were employed to identify pigments. The results revealed that emerald green, cochineal, ultramarine, orpiment, and red lead were used as pigments for green, red, blue, yellow, and orange colors on a golden leaf made of brass alloy. The study also demonstrated the mixtures of lead-barite white, lead white-ultramarine and lead white-red lead-indigo-cochineal in the white, light blue, and pink sections. While multi-band imaging was found to be a suitable tool for the primary classification of pigments, relying solely on this method without a complete pigment database is not advisable, as differences in underlying paint layers and mixed pigments can affect imaging results. Overall, the combination of imaging and spectroscopic techniques provides a reliable and non-invasive approach to identifying historical pigments and their alterations.

Abstract This study aimed to identify and classify the type of plants used for tanning historical leathers using cost-effective Fourier transform infrared (FTIR) spectroscopy. The investigation was carried out on five plants (oak bark, sumac, valonia, tara, and gallnut) and four historical leather samples from book bindings dating back to the Qajar period. Tannin extraction from both plants and leathers was performed using acetone–water solvent, and the samples were then subjected to FTIR spectroscopy. Pre-processing of the spectra included baseline correction, smoothing, and normalization. Principal component analysis (PCA) was used to identify the source of tannins based on FTIR results. FTIR was found to provide a good separation of condensed tannins from hydrolysable ones. However, PCA analysis allowed for the separation and identification of the type of plant used for tannin extraction. The examination of historical leather samples revealed that the primary classification based on the type of tannin is possible, but accurate identification faces challenges due to structural changes and degradation over time. Graphical abstract

Abstract This paper identifies the materials used to make a brocade belt belonging to the Qajar courtiers in Iran. This belt consists of two fabric types: red support and golden brocade. Accordingly, this paper examined the skin and tannin type, fiber types, dyeing agents, mordant, and metal wrapping of brocade yarns and metal buckle. Technical imaging, ESI–MS, FORS, FTIR and SEM–EDS were used to identify the materials. Multi-band imaging methods included Vis, UVL, IRR, and UVR, in which UVFC and IRFC images were obtained after processing. The results showed that cotton yarn was used in both fabrics. The red fabric yarns were dyed using cochineal and alum mordant. Also, the yellow brocade yarns were dyed using catechins-rich plants, and in this dyeing process, polyphenols and alum have been as mordant. Madder-dyed yarns are also found in parts of the belt. Examination of the metal wrapping of brocade yarns suggests using strips of copper-nickel alloy with a thin layer of gold-silver alloy. This secondary coating protects the copper-nickel strips and increases their golden luster. The leather analysis of the leather parts also indicated the using cattle/calfskin tanned with gallotannins. Belt buckle analysis also shows the use of brass alloy with a high percentage of zinc, leading to a golden sheen and the buckle desired strength. The results show the use of low-cost materials in the manufacture of clothing for the lower levels of the Qajar court.

Abstract The present study aimed to identify pigments used in writing and decorating a Qur'an manuscript related to the early years of the Qajar era, a royal dynasty ruling over Iran from 1789 to 1925. The pigments were analysed using µ-XRF, SEM–EDS, Raman, and FTIR spectroscopy. Also, various technical photography methods were used to study the pigments including visible-reflected (VIS), infrared photography (IR), ultraviolet-reflected (UVR), and ultraviolet-induced visible luminescence (UVL) along with infrared false color (IRFC) and ultraviolet false color (UVFC) methods. Carbon black, red lead, and indigo were identified as black ink, orange, and blue pigments, respectively. A mixture of red lead and vermilion was also detected in the red/orange ink. White lead and calcite were also used as additives in blue color. A cochineal-based pigment was also used as red ink in some parts of the manuscript. However, the evaluation of golden color showed two types pigments of gold and brass alloys in different parts of the manuscript. Copper carboxylate was identified as the product of the destruction of this pigment. According to the results of the study, technical photography methods along with spectroscopic methods are a good tool to examine manuscripts and identify included pigments and reduce the amount of possible error and the need for destructive sampling.

In this study, Fourier transform infrared spectroscopy (FTIR) and luminescence imaging were used to identify the coatings of seven Persian lacquer papier mache penboxes, of which two were contemporary, one was from the Pahlavi era, and four belonged to the Qajar era. First, FTIR was used to identify the nature of the coating. Then, UV-induced visible luminescence imaging at the spectral ranges of 420–680 nm (UVL), 425–495 nm (UVIBL), and 615–645 nm (UVIRL) was performed for further examination. The FTIR results showed that the coatings were made of alkyd resin, oil-resin varnish (Kaman oil), and shellac. In UV-induced visible luminescence images, synthetic alkyd resin showed no fluorescence, which made it distinguishable from the natural organic coatings. While it is slightly challenging to differentiate Kaman oil from shellac based on FTIR results, these two coatings can be easily distinguished by their fluorescence in UVL and UVIBL images. The results suggest that the combined use of spectroscopy and spectral imaging methods can provide substantial information about the organic coatings of historical objects.

The aim of this study was to identify the nature and cause of foxing spots in a historical manuscript. This manuscript was a Holy Quran from the beginning of the Qajar period and the end of the 18th century. Samples were incubated for 14 days and were evaluated for the presence of fungal activity. UV fluorescence photography, micro X-ray fluorescence spectroscopy and Fourier transform infrared spectroscopy were also used to investigate the characteristics and causes of foxing spots. The results showed that there was no fungal activity in the foxing spots of this manuscript. Based on the morphology of the stain in UV fluorescence photography, these foxing stains are of the Bullseye type, usually associated with metal ions. µXRF spectroscopy also showed a high accumulation of iron and copper at the site of these spots. This indicates abiotic foxing in this manuscript. Based on FTIR spectroscopy and peak deconvolution and fitting by Gaussian function, abiotic foxing increases the cellulose oxidation rate. Intensification of cellulose oxidation in foxing stains can be considered as one of the reasons for paper discoloration.

The aim of this study is to characterize fibers, spinning and weaving techniques of fabric remains found in Kuh-e Khwaja, a Parthian archaeological site in Sistan, Iran. For this purpose, 26 samples, including fabric remains (17 cases) and separate yarns (9 cases), were examined. The fibers were identified using light microscopy and FTIR spectroscopy, and the yarn twist directions, the angle of pretwist of the fibers, and the weaving pattern of the fabrics were examined by light microscopy. The results showed that a similar type of fiber was used for both warp and weft in each fabric. Among the study, 12 cases (46%) and 14 cases (54%) have been characterized as wool and cotton respectively, which indicates the prosperity of both agriculture and animal husbandry in the Parthian period in the Sistan region. The yarn twist directions in both warp and weft were the same in all fabrics and were Z/Z type, except for one sample (Z/S). Also, single-ply (21 samples, 81%) and double-ply yarns (5 samples, 19%) showed Z-twist and S(2z)-twist, respectively. Most of the fabrics showed a plain weave; however, warp rib, irregular matt, twill, basket weave, and also knitted fabric were observed among them. In addition, the results showed that wool yarns have a lower angle of pretwist compared with cotton yarns. Therefore, this issue can be used in the primary classification of fabrics found from this archaeological site.

Introduction: Biodegradation is one of the main degrading factors of leather artifacts. Determination of fungi and other microorganisms has vital importance for conservation of valuable objects made from organic materials. Usual classic techniques for identification of pathogens and fungi have some difficulties, but FTIR spectroscopy has been introduced as useful technique for characterization and determination of microorganisms. Materials and methods: In this study, historic leathers were related to the Seljuk period. The leathers were sampled in laboratory and fungi were cultivated in SDA medium. Genuses of fungi were identified according to macroscopic, microscopic and morphologic characteristics. Microorganisms were analyzed by ATR-FTIR spectrometer and differences of spectral properties were assessed. Spectral properties were assessed according to form and absorption region of peaks. Cluster analysis was used for evaluation of different regions and areas on the measured spectra.Results: Results showed the presence of Penicillium sp. (9 samples, 33.3%), Aspergillus sp. (5 samples, 18.5%), Cladosporium sp. (4 samples, 14.8%), Rhizoctonia sp. (2 samples, 7.4%), Trichophyton sp. (1 sample, 3.7%) and also one sample of yeast (3.7%). Two species of fungi remained unidentified (7.4%) and there was not any growth in 3 samples (11.1%). Spectral properties indicated to structural differences between microorganisms (fungi, yeast, bacteria). It showed characteristics of fungi genus and species in some cases.Discussion and conclusion: Active fungi induce decomposition, hydrolysis and decay of leather and its vegetable tannins. The decay leads to aesthetic change and health problems. Therefore, it is necessary to remove of fungi and appropriate treatment of leather artifacts. Application of ATR-FTIR spectroscopy had good results for identification of fungi, yeast and bacteria. Assessments showed the potential of ATR-FTIR spectroscopy for easy and rapid discrimination between microorganisms and specially fungi genus and species in some cases. This study indicated the possibility of developing FTIR–ATR spectroscopy as a reliable method for rapid identification of fungal pathogens. Advantages of the method showed that it was an appropriate technique for fungi evaluation in large scale. IR spectroscopy could help in identification and classification of fungi. Combining the advantages of FTIR spectroscopy with other used routine techniques, might improve the efficiency of fungal classification and identification. Chemical composition of the samples can be simultaneously analyzed. Chemical analysis by FTIR spectroscopy results to better understanding of fungi growth and complex chemical processes during fungal development and substrate degradation.