Monday, May 27, 2013

Course Iron Smelt - RESULTS

I ran a course here at Wareham over the weekend 'Introduction to Iron Smelting'
(see :  http://www.warehamfo...urse/index.html )

The two students were Jeff Evarts and Greg Eamon

The fellows built a very good clay cobb furnace and prepared most the materials on Saturday. The design was a pretty standard 'Short Shaft', about 70 cm tall and 28 cm internal diameter. The material was an even mix (by volume) of chopped straw, beach sand and dry potter's clay. The tuyere was a ceramic tube (kiln support), set at 22 down and inserted by 4 cm, 12 cm above a charcoal fines base.
Air provided by one of the industrial blowers the Early Iron group all uses, gated to roughly 800 lpm.

Charcoal was broken and graded maple and oak ( added separately), total of about 50 kg.
Ore was a mix of 'Barton's Run' limonite, DARC Dirt Analog and some rock ore from Quebec I had been given by Antoine Marcal. Total used was 30.4 kg.
The main smelt sequence ran over about 4 hours (plus burn down and extraction, maybe 7 hours total with the preheat). Our burn times were extremely consistent, averaging 9 - 10 minutes per standard charcoal charge. Ore additions started at 1 kg, peaked at 2 kg per charge.

The final bloom was extracted from the bottom of the furnace (rather than my more typical top extraction). With only two of us available for the smelt (Jeff took ill), labour was a bit short, so it was off to the hydraulic press!
This might have resulted in a bit more slag being forced into the surface of the bloom iron than would be normal. Later forging will tell on that.

The result of weighing after some rough compaction and cutting : total 10.4 kg. This represents a roughly 35 % yield - certainly great results.
The bloom does appear a bit crumbly, but the slightly lower temperature of the initial compaction (after running back from the furnace to workshop) may be part of the reason. There was no spark test made at this point.

Excellent work by our two latest members of the iron bloomery community!

    Resulting bloom, partially compacted and sectioned
  • crushing.jpg
    Furnace in foreground, Greg smashing ore in the back

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

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