-Viking Age Smelter-

Built for the Seax project.



These are the new double bellows about to be lined with the oiled canvas... I think they'll move sufficient air.



The Champlain valley was once a major source of very high quality ore... so clean in fact, that it was specified for the cables of the Brooklyn Bridge by the designer, John Roebling. The ore was roasted & then brought by train to a depot and unloaded over a period from the 1850's to the 1950's. Lucky for me they spilled a lot. :)



I built the first set of bellows with the expectation that I would discover flaws and make another.
This set is about 3.5 x 2 feet and rises about 2 feet. It was decided that not enough air was being produced.

This was due to several issues:

* Not enough volume.
The next set in production is approx. 6" x 3".

* Too much flexibility in the bellows fabric. (Oiled canvas.)
Solution is to add supporting ribs.

* Air leakage around nozzle connection.
Inspect & eliminate all small leaks.

The several historical illustrations depict air inlet valves on the top paddle of the bellows. While the thick leather flap I used on the trial bellows worked, it is much more efficient to place the inlet valve on the bottom paddle where gravity may assist in the crucial production of an effective air seal. I rather suspect that if every bellows depicted and produced after the Viking Age is constructed in this manner, we may begin to wonder if the hole depicted on, say, the Ramsund carving, isn't there to help imply "bellows," rather than realistically depict them. Here I will depart from convention and place my new inlet valves on the bottom paddles.



This is the first firing of the smelter, to cure the refractory and to roast the ore. Roasting helps make ore more friable and porous. It is kept at a temperature of 800-900 C (1475-1650 F) for a period of 4-6 hours. The furnace had no problem staying in this range so long as it was fed a steady diet of softwood.



Roasted Ore!



The smelter is finished & drying now. I used 3 large wheelbarrows of clay and 15 gallons of horsedung. There are supporting sticks inside the top of the smelter. It is approximately 11" x 27" interior. The tuyere is 10" from the bottom. While it dries over the next week or two I shall hopefully make some charcoal & a bellows...



Click here to see inside. That's the tuyere on top; the tapping arch is on the right.

I spent the better part of the day mixing the clay with the horse dung & lining the smelter. It has taken quite a bit of material to fill all the gaps in the rock. I will be aiming for something near a 12" diameter with a 3 foot interior height, with the tuyere roughly 1/3 from the bottom... right now the smelter is about 1.5 feet deep. I will probably line the completed smelter with 'lute," which is a mixture of charcoal dust & clay. According to the U. of Bradford site this reduces cracking of the clay during firing. As previously mentioned, the addition of horse dung to the clay seems to perform a similar function. Assuming the smelter works, I'd like to get as many firings out of it as I can...



Here are some of the crucible test pieces I made with the local clay. It seems to fire well; the one on the left is unfired clay mixed with horse dung. In the middle is a fired piece from the same mixture. The cracked piece is mixed with wood ash, which was another suggestion that came from some of the Neo-Tribal smiths. I have thus far only come across historical sources mentioning dung as an addition to clay, though I do suspect that if ash works too, it must certainly have been used. At any rate, the ash piece cracked when I was heating it with a torch. I am guessing that the fibrous nature of the horse dung mixture might help prevent such cracking. The horse-dung piece was fired to the temperature of 1600 F, which I suspect will be the middle range of the temperature the smelter might see in use. I would fire some to the mid 2000 F range which will be the interior temperature of the smelter in use, but my electric kiln won't go that high. I suppose that will simply have to wait until such time as I fire up the smelter...



This is the rock base around which the smelter itself will be constructed. So far I have found a great vein of local clay and tried a few experiments to get the refractory qualities satisfactory. I have thus far tried mixing wood ash with the clay and forming a crucible, which was then fired to about 1200 F, which would approximate the interior temp that the smelter might be taken to during the initial firing phase. The wood ash / clay bisqued quite well though upon heating with a torch it cracked. I am hoping to obtain a relatively permanent material for the smelter, so the crack is a small concern. I suspect that the uneven heating of the torch may have been a factor which may or may not occur when the smelter is fired. I will be obtaining some horse dung to mix with the clay according to Theophilus and experimenting with that before finally packing the refractory around the stone base.

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