Conservation procedure for the protection and treatment of chromolithographic prints on paper refined by coating

In conservation and restoration practice, the issue of chromolithographic prints on refined paper is a non-trivial area to which systematic attention has not yet been paid. The absence of reference sources and case studies on this subject results from the fact that these objects – artifacts and documents – have not been preserved in great numbers in collecting and memorial institutions, and not much importance has been attributed to them within such collections. The rarity of the preservation of valuable chromolithographs in collecting institutions is complicated by their often problematic condition and the frequent damage resulting from the specifics of the chromolithographic process. Although after continuous improvement it was possible to print on almost anything, the most valuable picture posters were printed almost exclusively on “refined” paper. The “refined” coating on this paper, characteristic of chromolithography, as well as the final, transparent “lacquer” layer, cause many problems in terms of restoration, and many physical and chemical risks arise from the layering and interaction of the materials used. The established conservation and restoration procedures in the common practice of collecting institutions have not yet taken into account these very specific issues. The conservation procedure itself involves both theoretical and practical aspects. The section dealing with theoretical aspects summarizes the knowledge necessary to determine how to design conservation and restoration interventions and what constitutes the proper care of chromolithographic prints on refined paper. The introductory section provides many tools for the identification of such prints, including an historical excursion into printing technology and the production of refined coated paper. Rich pictorial documentation serves as a visual aid for recognizing the basic (most common) types of chromolithographs and for identifying paper types based on the damage incurred. The theoretical aspects deal in more detail with the process of refining paper by coating it, with regard to the chemical composition of the substances used, and provides an overview of such binders and pigments. An overview of the factors influencing the degradation of paper is summarized in a separate text dealing with external degradation factors (humidity, temperature, light) and internal ones (hydrolysis of the glycosidic bond, oxidation and photochemical reactions of cellulose, oxidation and photooxidation of hemicelluloses, photolysis and the photooxidation of lignin). The theoretical starting points for the conservation procedures in practice therefore explain the operation of the methods applied in the procedure. The focus is on the preservation of prints containing acidic materials, i.e., on de-acidification methods, such as in situ de-acidification in vacuum packages, the Papersave Swiss technology, and the MMMK method. The optimal variants of the conservation procedures for chromolithographic prints on refined paper are presented in a practical methodological manual based on theoretical analysis of the issue. The first practical step is the macroscopic and microscopic analysis of the physical condition of the examined print and production of a digital record. The output of that procedure is the identification of the material and a thorough assessment of the recorded types of damage, as well as the stage of degradation. As a useful practical guide, a categorization of types of damage according to the conservation procedure they require has been prepared. The record of these facts is the starting point for each conservation protocol and yields supporting information for the choice of a subsequent conservation procedure. The proposed conservation procedures include pH measurement and the subsequent adjustment, gluing and follow-up care. The procedure concludes with a proposal for optimal storage