The following signs of deterioration are associated with the materials listed:
Bloom
This takes the form of a white powder that can be wiped off or a pale mistiness.
Cellulose acetate
Cellulose nitrate
Polyvinyl chloride
Cracks and splits
Casein formaldehyde
Cellulose nitrate
Phenol formaldehyde
Polycarbonate
Polystyrene
Polyvinyl chloride
Shellac
Urea formaldehyde
Crazing
Casein formaldehyde (surface crazing)
Cellulose nitrate (internal crazing)
Gutta percha (network of small cracks on surface)
Polymethyl methacrylate
Polystyrene
Urea formaldehyde (an orange peel effect)
Crumbling
Embrittlement
Fading and discolouration
Pigments can fade independently, leading to complete changes of colour.
Phenol formaldehyde, also dulls
Polyamide, tendency to yellow
Polymethyl methacrylate, sometimes discolours in light
Polyvinyl chloride, yellows and goes brown
Polyurethane, yellows
Urea formaldehyde, also dulls
Vulcanised rubber, often has a yellowish brown tinge