dan_sapper

"Snowflakes" between the emulsion layers may be voids in the gelatin caused by film production chemicals being out of balance, not being dispersed properly during manufacture of the film (not processing chemistry), or migrating/drying-out after processing. Rewetting the film causes the voids to close, at least temporarily. The voids may return as the gel structure loses moisture content. Your technique of rewetting and gentle drying is a good way to minimize problem, but you will need to reprint or scan the negatives before the snowflakes reappear.