What is a forge
The forge is the hearth upon or inside of which the fire is kept for the purpose of heating the iron. The forge provides a safe fire resistant structure in which to keep the fire, and to which a source of air blast can be piped to increase the heat of the fire. Most modern shop forges incorporate a chimney structure to remove smoke from the fire, out of the shop safely. The blast of air raises the heat of the fire in the same way as blowing softly on a small flame to help light a campfire.
The blacksmith's forge has remained similar in design and purpose for millenniums. Some of the differences being in the materials we now use to build our forges and the source of air supply and delivery. Despite its modern look, the modern forge works exactly the same as those of its predecessors.
A forge fire for hot working of metal
Over thousands of years of forging, these devices have evolved in one form or another as the essential features of this type of forge:
- Tuyere -- a pipe through which air can be forced into the fire
- Bellows or blower -- a means for forcing air into the tuyere
- Firepot or hearth -- a place where the burning fuel can be contained over or against the tuyere opening.
During operation, fuel is placed in or on the hearth and ignited. A source of moving air, such as a fan or bellows, introduces additional air into the fire through the tuyere. With additional air, the fire consumes more fuel and burns hotter.
A typical Scottish smithy at Auchentiber, North Ayrshire, Scotland.
A blacksmith balances the fuel and air in the fire to suit particular kinds of work. Often this involves adjusting and maintaining the shape of the fire.
In a typical, but by no means universal, coal forge, a firepot will be centered in a flat hearth. The tuyere will enter the firepot at the bottom. In operation, the hot core of the fire will be a ball of burning coke in and above the firepot. The heart of the fire will be surrounded by a layer of hot but not burning coke. Around the unburnt coke will be a transitional layer of coal being transformed into coke by the heat of the fire. Surrounding all is a ring or horseshoe-shaped layer of raw coal, usually kept damp and tightly packed to maintain the shape of the fire's heart and to keep the coal from burning directly so that it "cooks" into coke first.
If a larger fire is necessary, the smith increases the air flowing into the fire as well as feeding and deepening the coke heart. The smith can also adjust the length and width of the fire in such a forge to accommodate different shapes of work.
The major variation from the forge and fire just described is a 'back draft' where there is no fire pot, and the tuyere enters the hearth horizontally from the back wall.
Coke and charcoal may be burned in the same forges that use coal, but since there is no need to convert the raw fuel at the heart of the fire (as with coal), the fire is handled differently.
Individual smiths and specialized applications have fostered development of a variety of forges of this type, from the coal forge described above, to simpler constructions amounting to a hole in the ground with a pipe leading into it.
http://www.beautifuliron.com/smithforge.htm
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