Casein plastic
A plastic made from milk protein. It is one of the very few materials that pests eat because it is food.
What not to do
Water is unsafe on Casein plastic
Unsafe
Do not do this. The risk is established, and it is described below.
Evidence
Supported
Sources
Conserve O Gram 8/4: Care and Identification of Objects Made from Plastic
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That solvents and water must not be used to clean plastic, and that if in-depth cleaning is needed a conservator should be consulted. (states this directly)
In detail
Casein plastic is a protein-based material derived from milk, used from the early twentieth century for buttons, buckles, knitting needles, pen barrels and jewellery. It stands apart for a property no other plastic has. Because it is protein, it is edible. Conservation guidance warns directly that casein plastic may attract parasites, and lists it alongside the wood fillers in some phenol-based plastics as susceptible to pest attack. A button collection or a set of vintage buttons showing small holes or surface grazing has a diagnosis that no cleaning product addresses. It is also water-sensitive in a way most plastics are not, being a protein rather than a hydrocarbon polymer. The general plastics rule applies with more force: dry methods only, no solvents, no water, cool and stable storage, and inspection every six months for the pest damage the material specifically invites.
Why
- Casein plastic is explained by Damage versus soiling
Related
- Casein plastic is commonly affected by Frass and pest residue
Sources for this page
Sources
Conserve O Gram 8/4: Care and Identification of Objects Made from Plastic
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That casein plastic is a protein based material derived from milk which may attract parasites, that wood fillers in some phenol based plastics are susceptible to pest attack, and that objects should be monitored every 6 months with deteriorating objects removed. (states this directly)
Conserve O Gram 8/4: Care and Identification of Objects Made from Plastic
National Park Service, US Department of the Interior · Government or regulator
Relied on for: That plastics are subject to ageing and degradation, that the first visible signs are weeping, tackiness, discoloration, distortion, warping, crazing and embrittlement, that once present deterioration is rapid and irreversible, and that solvents and water must not be used to clean plastic. (states this directly)