The furnace provides a source of clear glass. The glass is kept at a little over 2000 F (about 1100C) at which temperature glass has the consistency of warm honey; it moves quite freely. A typical furnace will hold from 200 to 1000 lbs (~100 KG to 450 KG) of glass when full. The furnace is left on 24 hours a day and will be shut down only if maintenance is required. Most furnaces are "charged" or refilled with glass on a weekly cycle. It takes about a day after a charge before the glass is up to temperature and air pockets within the glass have worked their way out. (Not all furnaces work on this model).
This is a horizontal furnace that is usually heated with natural gas (or propane) and forced air. It allows glass to be reheated as needed so that work can continue on the piece. The glory hole is only lit when it is needed for use.
Normally there will be a yoke in front of the hole that help support the pipe while the piece is being reheated.
Annealer or Kiln
When glass piece is finished, it must be cooled very slowly to allow stresses in the glass to relax before it reaches room temperature. If the glass is left at room temperature to cool it will almost always crack. The Annealers are warmed up to about 950F (500C) prior to the start of the glassblowing session, and work is placed in the annealer as it is completed. When the annealer is full (or work has concluded) the annealer will be programmed to slowly cool the glass. A typical annealer program will take about 17 hours to return the glass to room temperature. If the work is thicker than normal, a longer cycle (sometimes spanning several days) may need to be used.
As well as handling completed pieces, annealers will often be used to warm up glass color for pickup (see Color section below), or to warm up partially completed work that the artists wants to continue to work with. Generally glass must be brought up to ~1000F before it can be introduced to the heat of the glory hole. (Some shops will have annealers dedicated for bringing color up to temperature. If available these will be called "pickup annealers".
A glass studio will almost always have a metal table called a marver. The main purpose of this table is to allow the glass blower to shape the glass by rolling it on the table. The marver also acts to rapidly cool the portion of the glass that comes into contact with the table which can also be useful when blowing out the piece.