Jim,

I'll show you how I store mine...but I'd advise against doing it that way. I'd also advise against storing them in the foam, like you're showing...after enough time, the surface of many dice will become damaged from the foam.

I can never remember the proper terms, but the materials that make up the older dice are not stable. Some of the old dice will crystallize...even to the point of totally disintegrating. Other older dice will "implode", and they will typically smell like vinegar. When you have dice that are in the process of deteriorating, the dice that are around them can also be affected.

I don't take my own advice, and I have the damaged dice to prove it . My advice is to store them in an open air situation...such as on a shelf where air can circulate around them. Preferably they should be in a place that doesn't get too hot, and they shouldn't be exposed to direct sunlight...and probably the less light, the better. And it's best that they don't touch each other.

Here's how ours are stored...

One day I was looking through the dice trays, and found this pair...

Here's some dice self-destructing...

These dice are crystallizing...if they look like this, and don't smell like vinegar, you can coat them with clear nail polish which will help to preserve them a little longer. (I don't remember any of our crystallizing dice ever smelling like vinegar).

These dice are imploding...and I'm not aware of any treatment that will help to preserve them....

Once they travel far enough on the road to implosion, they will pop their spots...

With nothing to lose, I tried clear nail polish on some dice that were imploding...I was left with very sticky dice...(Hacienda, El Cortez, Aladdin)

And some of our oldest dice are, amazingly, still in great condition...other than the fact that someone glued them together to make a lamp!! Normally I'd frown about them being made into a lamp, but they may be surviving because they are a lamp...not just a pile of old dice...!?!