This from the late Jeff's site:

HELP FOR CRYSTALLIZED CASINO DICE
For dice that are crystallizing, I recommend preserving the dice digitally (explained above), and then treating the dice with a clear lacquer. I have used a clear nail polish lacquer for years to preserve my crystallized dice, and the results have been very good. The crystallization has not worsened, and the dice, once treated, can be handled and viewed with greater confidence.

The main tips to remember when treating your dice is to use the lacquer sparingly (it does not take much to lightly cover each die), use a dabbing stroke on all logo's (swiping across a logo may smear and ruin it), and let them dry overnight before handling. It is a good idea to store any dice that are crystallized in the same conditions described above for acetate dice, but not directly with your acetate dice!