I'm powder painting with a fluid bed, using a color I've used a lot (getting down to 1/2" in the bottom of the jar). But the last few painting sessions, I"m getting string-like clumps of paint forming in the fluidbed and sticking to my jigheads. Ugly clumping on the jigheads as they melt on. Can the powder get hot from a number of hot heads being dipped? Can the powder get old? It doesn't look like moisture-caused clumps, but heat caused. Otherwise, the coverage is good and curing in a toaster oven making good results. But random clumps form at times. Any ideas? Any experiences like this? Thanks.