|I can only comment on beads I heat-treated myself|
|Re: Re: Dissections of "cherry amber" phenolic resin beads/interesting -- AnneLFG||Post Reply||Edit||Forum||Where am I?|
The dark veins can be due to oxidation on the exposed crack surfaces, or maybe intrusion of dirt, body oils, etc. Beads that are still amber yellow have dark cracks. The cracks form as the material slowly shrinks with time - the shrinkage happens since the chemicals are still reacting although very, very slowly. Small molecules that were in the chemical mix may also continuously diffuse out at the surface and add to the shrinkage. Some beads have no sparse cracks or veins at all so I assume they were from manufacturers that tweaked the formulas to reduce or eliminate the shrinkage problem.
Another aging effect that I found when exposing some yellow phenolic beads to the intense sun here in CA - the yellow color faded to a much lighter yellow after about a year. Since there were many different commercial phenolic products I expect we will find all sorts of color stability/ instability for beads made with them.