I have used steel molds for years and never had a problem with heat retention. I have avoided aluminum molds up to now but now I have to use one. I have a four cavity Aluminum NOE mold for a.38 Cal. 312 gr. bullet. I am having trouble keeping the mold hot enough to cast good bullets. I am heating the mold on a hotplate, not the spiral element type, but the flat top type. I heated the mold as high a temperature as the hot plate would go, then poured the lead into the mold as it was ON the hotplate. I tried filling just two cavities, but I still got wrinkles. Normally when I cast with one cavity steel molds, I can pour them and drop them so long as I work steadily. I am thinking that I might have to pour into the mold as it is being heated with a blow torch. My lead is at 770* and that is as hot as my poor old pot will go and the lead is coagulating during the pour. Can I ruin the mold by overheating?