It's a crap shoot. What david is saying that if you don't allow it to cure, you are basically interfering with the crosslinking by adding another coat premature. KLASSE contains solvents that will soften up the previous layer if not allowed to cure. Now if you did a back to back coat, you would not accomplish ANYTHING in terms of layering, and probably would not experience "gumming" because it would be just like applying a new coat as curing has just begun. But if you applied it say....half way between the full cure time, you might see this softening and gumming as a result of interfering with the cure. After the full cure, it will in fact layer.