Previous: Operating the smelter
After addition of ore was complete (49 lb), a little more charcoal was added, and then the level of charcoal was allowed to burn down. When the level of charcoal had burned down to near the level of the tuyere, the wall of the smelter was broken open. When the wall was broken out to below the tuyere level, molten slag ran out, leaving the bloom in the center of the smelter. The bloom was removed with tongs and consolidated by firm taps with hammers while the bloom rested on a stump. When the bloom had cooled to below welding temperature, it was cut into several smaller pieces for easier working. (Ideally we would have had a forge going so we could re-heat the bloom and do more consolidation.)
The bloom was black, heavy, and somewhat porous. It was difficult to distinguish between the iron and slag by eye, but grinding or cutting into the bloom revealed mostly solid iron, with many holes and a little surface slag.
Initial attempts to further consolidate the bloom were not successful. Even at yellow heat, the bloom fragments readily under the hammer. Pictures below show before and after an attempt to consolidate.
An attempt to consolidate a larger portion was partly successful. After a number of heats and carefull hammering, it became somewhat bar-shaped. Hammering had to be done very carefully to avoid breaking the bloom. (We found later that the forge had built up some slag, so even though the fire appeared good, it was not operating at peak efficiency. We were also using charcoal, so not able to heat the bloom as fast as in a coal forge.)
A later attempt to further consolidate this piece was successful! As the smith relates, "So I tried again in my forge with a portion of the sample we tried before. This time there was success. The differences were heat, heat, and heat (coal forge). It may also have been that there was less time at temperature because I was able to attain the required temperature relatively fast. I worked with only a portion of the bloom so that we can play with the remainder at a later date. I had tried to cut off about half of the bloom, but a smaller portion broke off during the cutting so I used that smaller portion. An interesting fact was that I started with ~ 8 oz. and ended up with ~2 ½ oz. losing a little over 2/3 of the original mass to scale and slag expulsion. During the process I did add some flux (borax), but not much."
(Large chunk on the left is remaining part of bloom from previous picture. Bar on right was formed from part of the bloom that was cut off.)
We still have several large bloom fragments to experiment with. I think other blooms may consolidate more easily than this one has, but at least we are getting usable iron!
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