Cooking virgin liguid plastisol the 1st time...it has to reach (best to exceed, at least by a few degrees, to be safe) 350F for the PVC to go through its change. Then cool a little and add flake. Cool to where the plastic can be stirred without whipping much air in, add flake and blend. Remelts do not have to reach 350, they only need to be heated so they're workable. Plastic only has to be cooked properly the 1st time (starting from virgin liquid). Flake is the most heat-sensitive component, which is why I've omitted flake from alot of my recipes.