I thought the same thing at one time ["...will warp all by themselves..."], but having seen plaques of the same series as those that are badly warped (such as vintage Vichy and Monte-Carlo) that are in their original state of preservation; I can only agree with those who suggest it's strictly an improper storage issue that causes the twisting and warping... as well as the blistering.

Examples in the BG Collection and CARO Collection are still like they were from day one.

Some examples of vintage M-C material that most of us are familiar with (as seen in Tegtmeier's "CASINOS" pages 121) are still in perfect condition.

I actually inspected a huge collection of this type material last year while on boad a yacht that made the crossing from the UK to Ft. Lauderdale where the collection was purchased by someone from Rio; the stuff looked just like it did 50 to 75 years ago... New!

I'm convinced it's storage and not time that caused the reaction in that type plaque... though I will agree mosts plastics (plastic-types) do start to breakdown instantly.

I still have no idea why some material embedded in Epoxy is blistered; unless it was blistered previously to being embedded.

Funny, that none of this older material was made to last for decades; but rather to be payed on the tables.

Day, explains what some improper storage/handling has done to M-C material which kind of explains the poor-condition material existing today.

JB