Plastic Corrosion of Collectible Miniatures
Swelling, brittling, discolouration, depolymerization, dissolution, and disintegration of thermoplastic miniatures and models caused by ultraviolet radiation and oxygen
Miniatures and scale models made of thermoplastics like polyethylene / polythene (PE) and polypropylene (PP), or polycarbonate / acrylonitrile butadiene styrene (PC/ABS) may be damaged by ultraviolet radiation and oxygen to such an extend that they become glassy and may disintegrate when touched. The legs of the antique, over 30 years old, Timpo Indian pictured above, spontaneously fell apart when the miniature was picked up. Upon closer inspection and careful bending of the broken parts, the right leg snapped just above the boot. The legs pictured to the left are from a similar Timpo Indian, but they show no signs of corrosion yet. These legs react elastic, they deform under stress, and return to their original shape when the stress is removed.
Plastic corrosion of miniatures typically results in the destruction and loss of component parts or entire figurines made of PE, PP, oder PC/ABS, because thermoplastics cannot be repaired with glue. Soldering with a hot air pencil is an option, but proves impractical when the broken parts are too small to handle.
Examples of Brittleness, Breakage, and Disintegration of Plastic Miniatures
- Buggey, 1:32 Timpo Toys
- Indian, legs, 1:32 Timpo Toys
- Indian, hand, 1:32 Timpo Toys
- Indian, torso, 1:32 Plasty
- Confederate Sergeant, torso, 1:32 Timpo Toys
- Wagon Driver, 1:32 Timpo Toys
- Stagecoach, 1:32 Timpo Toys
- Confederate Infantry, 1:72 Italeri 6014
- British Paratroops, 1:76 Airfix 01723
The process of plastic corrosion may be slowed by protecting the miniatures from ultraviolet radiation, but it cannot be stopped entirely. Highly sought-after antique miniatures are especially at risk, they may fall apart one day upon the slightest touch. Painted and varnished plastic miniatures may be better protected from the corrosive effects of oxygen than unpainted figures.
Metal miniatures suffer comparable damage from the effects of tin pest.
Brittling caused by solvent-based Paint
Aromatics contained in solvents and solvent-based paints dissolve plasticizers in plastics, making them brittle.