Tuesday, March 20, 2012

Smeltfest B

(Day ??)

Sunday proved to be one of the best all round days at a Smeltfest from the last several years. Participants had followed their interests, attacking several aspects of a general problem. There were four groups, all working around the edges of the rear smelting area at Germinal Ironworks.

Lee Sauder, assisted by primarily by Therese Kearns, repaired and fired the iron furnace again. After two full smelts on the previous two days, Lee hoped he had figured the right combination and sequence to produce a bloom from the magnetite ore. The first smelt on Friday had not produced much slag - or any iron. The second on Saturday had reduced the ore, but the product was a unforgeable cast iron.
Success! Roughly 60 kg of magnetite was reduced to create an un-compacted bloom at 17 lbs. On initial compaction (first by hand and then under the large mechanical hammer) the product was found to be a nicely consistent higher carbon metal. After more or less 'bracketing' the smelting process with the previous two (pretty much) failures, Lee was quite happy to have nailed the right sequence of working this new ore.

Lee (L) assisted by Steve Mankowski -
Compacting the bloom under the large mechanical hammer. (*)

Working inside the main shop, Skip Williams was preparing various samples of the earlier slags and bloom fragments for examination under microscopes. Skip better understands the various components seen at different stages of the ore to metal process. He kept pulling all of us over to have look and explain just what we were seeing - and how this could apply to our understanding of the overall mechanisms we were involved with.
Shelton Browder assisted with this, as well as working on another examination. An antique axe of unusual construction (at least to modern eyes) was polished and etched. This allowed some insights into historical use of bloom and wrought iron metals.

One of the large projects intended for Smeltfest this year was to experiment with a smaller re-melting hearth. Steve and Jesus Herandez worked on this. Jesus has a specific historic point of reference - Japanese swords from before roughly 1700. He explained that this marks the start of the direct bloomery tatara system. Before that point, the process involved producting a high carbon cast iron, which was then re-processed in a secondary hearth to remove excess carbon until the metal could be forged into blades. This step in the sequence is not very well represented in archaeology or documents, so is a bit of a mystery. He said that pre-1700 blades have a distinctive quality that distinguishes them from later ones. Modern methods are yet to duplicate this quality.
At Smeltfest 2011, archaeologist Tim Young (from England) had told us about ancient remains from England and Ireland which appear to be the result of a similar process. Therese had focussed part of her academic researches into studying of these hearths. Taken with Skip's early research and the Smeltfest 2008 work on the Aristotle furnace, this investigation suggests many possibilities.

The test re-melting hearth.
An ingot of high carbon steel is just being removed - created from cast iron material

My project for the day was working with the smaller Aristotle furnace. Although the group had done considerable experimentation here, both together and individually, it turned out that not many tests of *reducing* carbon had been undertaken. In a series I did with Gus Gissing (back at Wareham) two years back one of the tests had been using small pieces of cast iron from a failed smelt attempt. My duplication on Sunday once again showed that the Aristotle furnace could also be used to reduce the carbon down to a useful level. It appears the system first removes the bulk of the carbon present, then re-applies carbon to an amount that is regulated by the way the furnace is physically set up inside. This may be a significant discovery.

The Aristotle furnace in operation - early in the sequence.

Of course, this is just some of the overall work and experimentation that goes on during a typical Smeltfest! Not to be discounted is all the time for conversation and sharing of ideas and problems.

(*) The process used to convert this raw bloom into something ready for further forging illustrates once again why part of my own OAC project has included some work on a hydraulic press. The hot bloom is pulled from the furnace, and its surface worked over with sledges on a metal plate to break off the loose 'mother' slag coating. This is done working on the ground, the strikers squatting almost African style. Then the exposed bloom is rushed to the forge to re-heat. Further compaction, from a half bowl to a slightly flattened puck, is done with a pair of strikers wailing away with heavy sledges.

Shel and Steve (L & R) using sledge hammers for the first compaction steps, working under Lee's direction.

Next, Lee moves over to his massive (200 + lbs) mechanical hammer to reduce the puck to a block. This is then cut into quarters, again under the mechanical hammer.
(as seen above).
Obviously, I personally do not have access to either the skilled labour, or more importantly, the large power hammers that Lee has. The new hydraulic press is thus critical to my ability to work similar large bloom masses.(Which of course is what the OAC Grant is all about!)

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February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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