Short Shaft over Slag Pit

October 9, 2011
DARC Smelt Team, Neil Peterson recording

The furnace was our standard short shaft type, roughly 25 cm interior diameter, 70 cm total height.
Walls were clay and straw cobb, about 8 cm thickness.
Fuel was hardwood charcoal (mainly oak) graded to .5 through 2.5 cm diameters.
Air volume via the tuyere (set at 20 cm above base) was roughly 800 litres per minute.

Holes were drilled through the furnace walls at roughly every 10 cm, starting at 10 cm above the interior base.
Measurements were taken using an industrial quality digital pyrometer (HH12B from Omega equipped with standard bare metal type K thermocouples).
The probes were inserted roughly 5 cm beyond the interior surface of the furnace wall.
Measurements were taken roughly every hour over the course of the smelt event.

Because the probes did not reach into the central core of the furnace, there is every possibility that the central furnace temperatures were even higher than what was recorded.
Our thermocoples failed (melted!) at roughly 1350 C. On several recordings, this temperature was reached.