Care and Repair of Vintage Plastics
Care of Plastics
Celluloid is subject to degradation via heat, acids, alkalis, and UV light. It can quite literally disintegrate when kept in poor conditions. The most harmful environmental agent is moisture, as water is required for all of the aforementioned chemical reactions. Keep your celluloid game pieces in a cool dry location, and ensure good air circulation. Consider adding packets of silica dessicant to game cases containing celluloid pieces. If it needs cleaning, I use a cloth slightly dampened with either water or isopropyl alcohol, drying carefully afterward.
Bakelite holds up well over time. UV light causes it to discolor over time (see Aging of Plastics), but that discoloration is superficial. Catalin shrinks over time, which is why catalin radio chassis will warp, and translucent and enrobed mah jong tiles are susceptible to cracking. Both can be cleaned with water, but when cleaning mah jong tiles I use isopropyl alcohol to avoid damaging their paint.
Repair of Plastics
I use slow-setting epoxy with good flexibility for phenolic plastics. This should accommodate catalin's shrinkage over time. Epoxy can be tinted with acrylic paint to color match the material, then by sanding and polishing, you can have a near-invisible repair (see pictures here).
I have used Duco cement (nitrocellulose) to re-glue celluloid (cellulose nitrate) faces that have delaminated from hardwood Mah Jong tiles. I have also read that acetone or celluloid dissolved in acetone can be used as a glue for celluloid. It seemed a bit tricky to me, so I haven't tried this.