The glass furnace stands in the middle of the Cone. It is circular in shape and measures about 7m in diameter and is 3m high. Around 40 men and boys worked in this furnace at one time. The furnace operated continuously for 24 hours a day, 365 days a year.
The Lehr or Annealing Oven was a long, brick-lined separately heated tunnel through which the finished glass pieces travelled. It controlled the cooling of the glass; if the glass was cooled too quickly it could crack or break. The time allowed for annealing varied with the bulk of the items; the thin glass pieces require only a few hours whereas the large and thicker glass pieces need a longer time.
The Lehr had shallow iron trays that held the finished pieces of glass. The glass cooled slowly as it travelled through the Lehr on a winding chain mechanism rather like a conveyor belt you now see in supermarkets.
The Lehr at the Red House Cone is the only remaining example in the world.
At the cold end of the Lehr (or annealing oven), the glass emerged into a room known as the Shrower. Here the glass was inspected by women for any faults and then sent to other departments around the site for decorating, finishing and packing. Any damaged pieces were rejected, broken up and recycled as cullett.
It was not unusual for young children to be crawling underneath the mechanism to keep the chains working beneath.
During the first half of the 19th century, glass was taxed by weight and an excise officer or taxman was stationed in a booth to supervise the weighing of glass as it came out the Lehr. The Shrower was kept under strict lock and key so that no goods could be removed before they had been weighed.
The manufacturers bitterly resented the presence of these Taxmen and they became known as 'Watchdogs' sitting in the 'Doghole'. The managers had to give written notice of virtually every operation of the factory and if the Taxman could not attend straight away the whole production process had to be delayed.
