....which isn't much. A scan of the structure of polyvinyl chloride is
shown below, in case anyone was interested. The "n" in the scan just
represents some number of those units shown in parentheses.

My thoughts on the problems people are having with PVC holders is this:
PVC is a very hard substance. Plasticizers are added to PVC to make
it pliable and to reduce the interactions of the chains on each other.
Plasticizers eventually evaporate. (You know that "new car smell" that
everyone loves? That is the smell of the plasticizers evaporating from
the plastics in your car).

My bet is that it's the plasticizers that are causing the problem. I
don't know what chemical is used as a plasticizer but when I find out
I'll try to see if there is a possible reaction going on between it and
the chip to cause damage like that of Bob's chip. PVC itself is pretty unreactive.

I don't know what modern and older chips are made of. I know you
mentioned clay....what else is used?

Very interesting thread....seeing how I store all my chips in binders
and the 80 pocket binder that Don mentioned....I'd kind of like to know
for myself what is going on....

Katie