Isinglass

Isinglass is derived from the dried swim bladders of fish, with Salianski Isinglass being the highest grade available. In the Russian Icon tradition, it commonly provided the glue component in gesso recipes, and was sometimes mixed with pigment to make tempera paints, due to its high binding strength. It can be used to make a pale, clear glue, which is less prone to darkening than other animal glues, and which is particularly flexible, making it a useful material for repairing textiles.