Pre-industrial Iron Symposium October 10, 2004
Experiment Notes - Viking Age Smelter


BellowsMichael Mahoney
Millard Wyman
Paul Bourdon (not shown)
LeaderDarrell Markewitz
Recorder Elizabeth Hendrix

Drawing
Drawing
Overall Measurements Diagram of Results

TIME EVENT MEASUREMENT
Absolute Relative Elapsed Relative Absolute Total
2:00 pm slow preheat with split soft wood fire
3:45 1:45 prep of bellows (attached to tuyere)
3:50 1:50 start of bellows, split soft wood - various users +/ - 60 /min 120 l/min
4:17 2:17 end of pre-heat phase
4:17 fill furnace with prepared charcoal air: 60/min 130 l/min
fuel: 60 cm 5275 cc 5.3 l / kg
4:32 0:15 15 min add charcoal air : 60/ min 130 l/min
fuel : 10 cm 880 cc 6.2 l
4:37 17 minbellows operator changed
4:42 0:25 optical pyrometer reading 2720 F
4:44 0:27 12 min add charcoal fuel : 10 cm 880 cc 7.1 l
4:48 0:31 air rate measured air : 72 /min 160 l/min
4:53 16 min bellows operator changed
4:57 0:40 13 min add charcoal fuel : 10 cm 880 cc 8.0 l
4:59 6 min bellows operator changed air : 54 /min 120 l/min
5:07 8 min bellows operator changed
5:11 4 min bellows operator changed
5:16 5 min bellows operator changed air : 60 /min 130 l/min
0:59 19 min add charcoal fuel : 10 cm 880 cc 8.9 l
5:29 13 min bellows operator changed air : 72 /min 160 l/min
5:32 1:15 ore charge (one) ore : 1.5 kg 1.5 kg
16 min charcoal charge on top fuel : 5 cm 440 cc 9.35 l
5:41 13 min bellows operator changed
5:42 1:25 optical pyrometer reading 2660 F
5:44 crack in smelter wall patched
5:47 1:30 15 min ore charge (two) ore : 1.5 kg 3.0 kg
charcoal charge on top fuel : 5 cm 440 cc 9.8 l
5:53 tuyere blocked / cleared with rod
6:01 1:43 14 min ore charge (three) on rear half only ore : 1.5 kg 4.5 kg
charcoal charge on top fuel : 5 cm 440 cc 10.25 l
20 min change of bellows operator
6:05 tuyere blocked / cleared with rod
6:06 increase of bellows delivery pressure air : 72 /min 160 l/min
6:11 6 min change of bellows operator
tuyere blocked / cleared with rod
6:15 1:57 13 min ore charge (four) on rear half only ore : 1.5 kg 6.0 kg
charcoal charge on top fuel : 5 cm 440 cc 10.7 l
air : 60 /min 130 l/min
6:18 larger crack in furnace repaired
6:23 5 min bellows resumed
6:26 15 min change of bellows operator
6:27 optical pyrometer reading 2200 F
6:29 tuyere blocked / cleared with rod
6:32 2:14 17 min ore charge (five) on rear half only ore : 1.5 kg 7.5 kg
charcoal charge on top fuel : 7.5 cm 660 cc 11.4 l
6:44 18 min change of bellows operator
6:46 2:28 14 min charcoal charge added fuel : 7.5 cm 660 cc 12.1 l
6:50 6 min change of bellows operator air : 72 /min 160 l/min
6:55 5 min change of bellows operator
6:58 2:40 14 min charcoal charge added fuel : 10 cm 880 cc 13.0 l
7:04 optical pyrometer reading 2680 F
7:12 2:54 14 min charcoal charge added fuel : 7.5 cm 660 cc 13.7 l
7:20 25 min change of bellows operator
7:24 4 min change of bellows operator
3:06 12 min charcoal charge added fuel : 5 cm 440 cc 14.2 l
7:29 repair of crack in smelter
7:30 3:12 6 min ore charge (reduction fines) added ORE : .5 kg ( 350 ml) 8 kg
fuel : 5 cm 440 cc 14.7 l
7:40 slowing of bellows rate during repair
7:50 26 min change of bellows operator, rate continues slow
7:53 3:35 17 min final charcoal charge added FUEL : 5 cm 440 cc 15.2 l
8:15 25 min change of bellows operator, rate continues slow
8:25 10 minchange of bellows operator, rate continues slow
8:40 4:05 end of firing
8:40 start scooping remaining charcoal from smelter
8:45 4:10 5 min bloom / slag bowl exposed
8:54 4:19 9 min bloom / slag mass extracted from smelter


AIR : Calculated against earlier measurement to fixed volume / note variation by operator : 2.2 l per stroke (average)
FUEL : Calculated by height at fixed furnace dimension of 28 cm diameter : 87.9 cc per cm
ORE : Total of 17.5 lbs / 8 kg roasted ore was prepared / charges estimated individually by volume : 1.5 kg per charge

Patching : Each time a hole / crack was patched, the bellows was stopped for the time required, typically about 2 - 3 minutes
Clearing : Each time the tuyere was cleared, the bellows was stopped for the time required, typically about 1 - 2 minutes
Operator : There were a number of people who assisted in bellows operation, especially during the pre-heat phases. There was considerable variation in rate, loft and pressure between these. Typically these are represented by the short bellows operator times. From the begining of the ore charge phase, the three primary operators rotated, delivering a much more consistant and controled rate / loft / pressure.

All text © 2004 Darrell Markewitz - the Wareham Forge