Type metal, an alloy of lead, tin and antimony, is seen here in the pot at the right of this Monotype casting machine. The metal is held at 535ºF or thereabouts so it can be squirted into the type mould and matrix to quickly cool and form the sort. It is alleged that you can stick your finger in and quickly out of the pot without getting burned, as your finger is cooler the type metal creates a sort of metallic finger-mould/shield around it without the temperature getting high enough to harm you. Needless to say it is hard to find anyone who confesses to having done this. It seems to me, if true, it would have to have been a sort of rite of initiation for apprentices, but the one who told me about the possibility of finger-dipping stoutly denied any ritual hazing in the modern printshop.
After dissing, the type is melted down and formed into ingots like these, with a hook on one end so they can be hung over a hot pot and melted for reuse.
There’s already a post on Making Book about casting type, with videos — 9 July 2015