Letter Re: Bullet Casting: A (Relatively) Simple Introduction, by AVL

Another safety item for melting lead: When done pouring bullets, it is important that any remaining lead should be poured out of the pot, rather leaving it to solidify in the pot. Lead like all other materials will expand when heated. Lead will also melt from the bottom up and if trapped by a solid layer at the top, may erupt when it breaks through that top layer. – R.H.