I asked SGC, and they are not airtight.
I believe PSAs slabs are also not airtight.
Now whether they have enough air transfer to prevent problems is another thing. We do know that there are PSA slabs with acidic cardboard that have been sealed for over 25 years, and they seem fine. But archivists look for more.
Quote:
Originally Posted by SetBuilder
Are slabs airtight?
I was thinking about this the other day when it comes to slabbed Old Judge cards...
Those cards have organic material on the surface that is basically decomposing very very slowly and releasing tiny amounts of gas (sulfur?). If the air is trapped inside the slab and can't circulate, then it is probably speeding up the decomposition of the images.
I read an article that the Hall of Fame removes all cards from slabs because they're not sure what the long term effects are.
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