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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. [ABSTRACT FROM AUTHOR]

This study aims to explore the potential of µ-Raman and µ-XRF spectroscopy for discriminating between various obsidian sources found in northwest Iran and to trace the provenance of prehistoric artifacts discovered at archaeological sites close to these sources. The study utilized excitation lasers of 532 and 785 nm to analyze obsidian samples from different sources, including Tajaraq (Miyaneh) associated with the Bozqush volcanic mountain range and Ghizilja (Bostan Abad) and Ideloo (Sarab) linked to the Sabalan volcanic mountain range. Principal component analysis (PCA) and hierarchical clustering (HCA) were utilized to analyze the data. Archaeological sites that were examined in the study were Kultepe Asbfrooshan of the Chalcolithic and Kura-Araxes cultures and Tepe Emam Chay of the Bronze and Iron Ages. Micro X-ray fluorescence (µ-XRF) was used to check the viability of the Raman use in discriminating the sources of obsidian. Results indicate that Raman spectroscopy is an effective method for differentiating sources of obsidian and confirming the origins of ancient tools from Ideloo. These findings suggest that local obsidian sources had limited usage, and it is crucial to explore and identify other possible sources of obsidian to comprehend ancient obsidian trade networks fully. The paper establishes the significance of using Raman spectroscopy in determining the provenance of obsidian artifacts and the complexities involved in the geoprocessing and trade of obsidian. A more comprehensive investigation of potential sources in the region can help unravel the trade dynamics of ancient Iran. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]