mah jong rack
casein chip
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The Aging of Plastics

Phenolics: catalin and bakelite

As bakelite and catalin age, UV light causes a layer of phenyl alcohol to form on its surface. Phenyl alcohol is yellow-brown, so it imparts that tint to the original color. Thus cobalt becomes "blue moon" to olive green (see photo below), bright red becomes mahogany, white becomes butterscotch. Phenyl alcohol is an excellent sunscreen, so the discoloration only penetrates a millimeter or so. These plastics are very resistant to chemicals, and will never melt or ignite. Catalin, however, will shrink over time. This can result in warping and cracking of the piece.


As I mention in Care of Plastics, celluloid is prone to significant changes with age. It can yellow with time, turn pinkish-brown, crumble, and implode.



Casein can lose moisture over time, and sometimes you can see this as a subtle "crinkle" on the surface. My casein Mah Jong set doen't show this, however, and so far appears to be pretty bulletproof.


Roll over the thumbnails for a larger image.

mah jong rack catalin tile celluloid tile casein chip
Catalin mah jong rack - sanded to reveal original color
Catalin tile - shrinkage over time can lead to cracking
Celluloid tile showing discoloration most prominent on the sides
A casein mah jong betting chip - moisture loss leads to surface texture change


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