Glasmaking furnace, c 1500.
© Science Museum / Science & Society Picture Library
Model of a furnace described by Georgius Agricola (1494-1555), in his book 'De Re Metallica'. The furnace consists of two levels, with a fire at the base. Immediately above the fire, ceramic pots held batches for future melting; while at the top, containers designed for cooling glas were stored. The furnace also had windows through which blowpipes could reach the molten mixture.