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This paper presents the results of a series of tests – using a recently-published set of methodological guidelines referred to here as the Protocol – on varnishes traditionally used in the protecti...

Understanding the use of colorant materials throughout history is now the objective of multiple studies centered on the identification and characterization of these materials. The main objective of...

This work was supported by the research group "Ciencia y Cultura del Patrimonio"(HUM-1057) and the Ministerio de Economia y Competitividad in the framework of the I + D research project "Nuevas alternativas al conocimiento de los materiales y los procesos de conservacion y restauracion de obra grafica y patrimonio documental"(REF.MAT2014-58659-P). Funding for open access charge: Universidad de Granada/CBUA., This study offers a new tool to restorers to bleach paper documents: artificial light radiation (ALR). It is a controlled method that is an alternative to other highly aggressive procedures that have been applied to cellulose based media. Its main novelty is its intrinsic lighting characteristics which guarantee uniformity and avoid heating the paper. The results of testing this new tool were compared to those of bleaching with hydrogen peroxide (H2O2). Each of the two methods was applied to five different types of widely used paper: Arches and Somerset (brands serving for engraving and digital printing), Ingres (drawing), press-type (magazines and newspapers) and Bible-type (historical documents). Once characterised by physico-mechanical, chemical and optical parameters (grammage, thickness, specular gloss, optical properties, air permeance, tensile properties, determining the pH of both surface and aqueous extracts), the different papers were bleached by the two methods according to pre-established criteria. Finally, to determine the evolution and effects of the two treatments, the papers were subjected to accelerated ageing., Research group "Ciencia y Cultura del Patrimonio" HUM-1057, Spanish Government MAT2014-58659-P, Universidad de Granada/CBUA

This paper presents a method and protocol for the study of varnishes and be protective layers applied throughout history to graphic works. The study is based on the characteristics and behaviour of varnishes when facing different types of deterioration. The methodology is founded on a series of physical–chemical tests that identify the characteristics of a varnish when applied to paper (surface and total drying time, degree of adherence, and penetration into the substrate) and in treatments, determining its resistance to adverse conditions of humidity, temperature, and light (resistance to humidity, immersion in water, and ageing by dry heat or in a climatic chamber). The effects of these tests are evaluated by taking into account a series of physical–chemical parameters characteristic of varnishes on graphic works: weight, dimensions, thickness, texture, optical features, and pH. Variations among these parameters serve to measure the resistance of varnishes to adverse conditions and natural ageing, whether they are applied as a conservation treatment or historically. All the information necessary to facilitate the transfer of this method to researchers and professionals is compiled in a protocol. This document comprises general information, descriptions of procedures and materials, and a series of annexes that serve simultaneously to collect and to study the data. The protocol is therefore designed to serve both as a tool when applying the method and as the germ of a database for the study of varnishes on graphic works. Shellac varnish was selected to test the method and the protocol. This resin has been used in the past to provide a waterproof varnish for paper-based maps as well as for images. Errors identified during the development of the protocol were ultimately corrected by incorporating new tests, items, and annexes. The protocol has proven to be a practical tool for the study of varnishes regarding their behaviour in the case of graphic works.