Annealing Oven: a Firebrick Chamber over a Firebox

Annealing is holding work hot and letting it cool slowly so it loses its stresses or softens. Glass is held at about 454–482 °C for most kinds, then cooled slowly; metal is often left to cool in the oven with the fire out. Build a firebrick chamber over a small firebox, with a door, a damper and a pyrometer, so it can be held at heat and then shut up to cool. The picture: putting bottles into the annealing oven at a glass works, 1908 (Lewis Hine).