"It's made from flour and animal glue.
"It's held together with animal glue," he said.
Distemper — pigments suspended in water-soluble animal glue — is tricky stuff.
Animal glue traditionally has been used in wood joining, book bindery, sandpaper manufacture, heavy gummed tapes, and similar applications.
A broad category of cultural heritage objects are multilayer structures composed of organic, humidity-sensitive materials – wood, animal glue, paper, leather, bone or paints.
These include polysaccharides (opuntia, also known as nopal used either as a powder or as mucilage), proteins (animal glue and casein) and fatty acids (olive oil).
The hydroxyproline is the marker of the animal glue.
Animal glue is believed to be the adhesion material.
Typically, the residual ash was mixed with animal glue, and applied either directly to the canvas or after a thin layer of animal glue.
Among these are egg, animal glue, polysaccharide gums, plant resins, fats or oils and beeswax.
This might explain why no animal glue was identified in these samples.
