Before revision: An opening near the base served to insert a pipe of pen shapable material whose purpose was to direct the air blast to either the furnace or crucible, and which was usually done through the mediation of a tuyère.
After revision: An opening near the base served to insert a pipe of perishable material whose purpose was to direct the air blast to either the furnace or crucible, and which was usually done through the mediation of a tuyère.