Experiment Notes - Norse Short Shaft Smelter in a frame

Reports of all of our iron smelting efforts along with more articles and information are available on the "Iron Smelting in the Viking Age" CD from the Wareham Forge.  Copies of the CD can be purchased here.

The bloom was less consolidated on extration than what is seen from a smelter with an insert tuyere - more of a 'lumpy' texture. It also was positioned a bit futher back from the air inlet than expected, and had a marked crescent shape. As with the Thanksgiving smelt (which also used the plate / hole) there was a choke point at roughly 2 1/2 hours into the ore charging / about 7 kg. The developing slag bowl threatened to drown the air intake. On this attempt we were better able to control this, and the smelter would settle down once the slag evolved from the early green silica type to the later black iron rich type.

Conclusions:

Overall set up

As with the thanksgiving smelt there were no particular problems with this working arrangement.

Use a bellows plate construction & Use blow tube arrangement for the tuyere

It was clear that the team needs more experience working with this type of furnace set up. In itself, the bellows plate was found to work extremely well. The thinner material did in fact withstand the higher temperatures surrounding the air blast quite effectively. Leakage around the plate was due to clay shrinkage, as the body of the smelter had been baked dry before the plate was installed. Fitting the plate while the body of the smelter is still damp is expected to greatly reduce (if not totally eliminate) this effect.

The blow hole arrangement proved to be more of a problem. It was clear that the system was working correctly for the first portion of the smelt sequence. Consumption rates were slightly reduced from those seen with the insert tuyere, but still within what was considered the effective range. (A rate of between 6 - 12 minutes per 2 kg charcoal is sought, for this experiment the rate averaged 13 minutes per charge.)

Problems were encountered as the slag bowl began to reach the level of the air hole, Attempts to clear the hole were compounded by the restricted access because of the bellows frame combined with the lack of experience on the part of the operators with this type of air system. Modification of the air tube and adapting the air hole to correctly fit should be made (in line with suggestions by Michael Nissen)

The production aim for this experiment was for a 3 - 5 kg bloom, similar to those suggested for Hals (size in range of 15 x 15 x 10 cm). Despite the early problems with the blocked air hole, the team produced a 4.25 kg bloom.

Taking measurements	Rodding out	Blockage building up	Inside view
Overlapping tappings	Salg tapping	Removing charcoal	Preparing thumper
Thumping	Main bloom mass	Secondary bloom	Front wall
Anatoli sketching

Reports of all of our iron smelting efforts along with more articles and information are available on the "Iron Smelting in the Viking Age" CD from the Wareham Forge.  Copies of the CD can be purchased here.