Comparative analysis of the properties of natural adhesives for strengthening the paint layer in restoration of easel oil painting on canvas

This article presents the results of studies of three natural adhesives that can be used to strengthen easel paintings on canvas: sturgeon, rabbit and funori. On the one hand, these are two common protein substances that have been used since the earliest stages of restoration practice, and on the other, funori, a polysaccharide of oriental origin, the use of which for strengthening the paint layer began several years ago. The chemical composition of the adhesives was studied using IR spectroscopy, and the following parameters were analyzed: pH level of adhesive solutions, viscosity, hardness, moisture absorption, strength and gloss. Funori demonstrated high viscosity and elasticity, high water absorption ca-pacity, and resistance to mold growth. It requires pH control due to potential contamination during its production. Sturgeon glue remains the optimal traditional material with high adhesive properties, while rabbit glue has a lower pH and is more hygroscopic. The addition of honey to gluten adhesives improves their flexibility but increases the risk of mold growth and makes them unstable under changing humidity conditions. The research results highlight the need for a comprehensive approach when selecting a reinforcing adhesive, considering its chemical and physical characteristics required for specific restoration tasks.