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Charcoal Air Furnace for Crucibles, Drawn by a Chimney
The chemist's furnace for melting in crucibles needs no bellows: a firebrick box closed on every side, air entering only under the grate, and a tall chimney to draw it through the burning charcoal. George Fownes (1856) describes it; a sliding damper in the flue sets the heat, from dull red upward.
The picture: a 16th-century assay workshop woodcut with wind furnaces, one on a tripod, for melting silver in crucibles (Deutsche Fotothek).
Intermediate
Two days, plus drying
Instructions
1
1
Fireclay mortar
Fireclay mortar
Mix fireclay and fine sand with water to a stiff, smooth mortar (our mix: about one part clay to one of sand).
Materials for this step:
Refractory Clay10 kg
Fine Sand10 kg
Water8 litersTools needed:
Bucket
Hand Trowel2
2
Ash pit and grate
Ash pit and grate
Lay a level firebrick base and build a low ash pit with an opening at the front. Forge bars from wrought iron rod and set them across the top as the grate, a finger's width apart.
Materials for this step:
Firebricks20 pieces
Wrought Iron Rod2 mTools needed:
Hand Trowel
Spirit Level
Blacksmith Forge
Cross Peen Hammer3
3
Fire box
Fire box
Build a square box of firebricks on the grate, wide enough for a crucible with a hand's width of charcoal all round, and tall enough to cover it. Joint every brick thinly with the fireclay mortar.
Materials for this step:
Firebricks40 piecesTools needed:
Hand TrowelSpirit Level4
4
Flue, chimney and damper
Flue, chimney and damper
Lead a flue out near the top into a tall chimney pipe. Fit an iron sliding plate across the flue as a damper. Close the top with a loose firebrick lid.
Materials for this step:
Chimney Flue Pipe1 piece
Iron Sheet (Hammered)1 pieceTools needed:
Hand Trowel5
5
Dry and first fire
Dry and first fire
Let the mortar dry for days, then light a small charcoal fire and raise it slowly over an hour or two so the joints do not crack.
Materials for this step:
Charcoal10 kgTools needed:
Heat-Resistant Gloves6
6
Draught from the chimney
Draught from the chimney
Loading Jupyter Notebook...
7
7
Limits
Limits
The principle and the damper are Fownes's; the sizes, the mortar mix and the draught formula's working figures are ours. Charcoal fires make carbon monoxide: work outdoors or under a good chimney.
Materials
8- 10 kgPlaceholder
- 10 kgPlaceholder
- 8 litersPlaceholder
- 40 piecesPlaceholder
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- 1 piecePlaceholder
- 1 piecePlaceholder
- 10 kgPlaceholder
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