Tap slag
Slag that is 'tapped' from a bloomery furnace. This is carried out during smelting so as to allow the long continuance of the operation. It cools to a solid slag with marked flow lines. 'Tapping' of bloomeries has been carried out since the Roman period - before Iron Age smelting formed other slag, called hearth bottoms, removed at the completion of every short smelting.
To explore more glossary entries click on a letter.