I haven't poured a lot of palm pillars, but I've poured a few. I have never preheated the molds. I use aluminum molds, and pour about 200 and let them sit. They turn out great every time. Pillars and votives. I use the natural crystal palm wax from Candles and Supplies. I have the warmest room in the house, and I generally can't stand the wait so I pull them out of the molds maybe an hour after the sides pull away from the mold. They're still VERY warm at this point. Can't pull the wick pin out, or the center will drain out. (Not very cool!) Maybe try covering them with a cardboard box when cooling? Or try to keep them in a warmer room? I think I read here someone tried them in metal molds and they wouldn't get a pattern, then they switched to aluminum molds and got the results. Seems from what I've been reading, the slower the cooling, the better the patterns. sorry for the ramble!