Isinglass in almost transparent yellow flakes, made from untreated Russian sturgeon bladder. Glues of animal origin are easy to use, resistant to ageing, re-solvent upon heating and therefore particularly easy to repair. Unlike synthetic glues, they can be easily enamelled and etched. Also suitable as a base coat for painting and gilding.
Adding cold water allows you to macerate the glue and then gently heat it in a water bath.
Given the limitations of the fishing quota, this is a real rarity.