I’ve not had a problem with white, but I have had problems with the slightly off-white (almond?) colored System 96. I try to use it capped with clear if I can.
If you are using any kind of paper for a glass separator, I would try kiln wash. Note however, that kiln wash will be more likely to stick to the back of opaque glass, and I have particularly had problems in this regard with white.
Jester’s Baubles Fused Glass Designs