The prototype is Culduthel, Scotland, circa 200 - 400 AD.
The furnace is a 'slag room' type, with a clay shaft built on a withy frame, over a stone base. The general details of the layout were similar to other Late Iron Age / Viking Age furnaces built in the past. The material used was a 50 / 50 mix of dry clay and course sand.
(See the earlier post : Scottish Dark Ages Iron Smelt )
This smelt was a test / training for the 'Turf to Tools' project being undertaken at the Scottish Sculpture Workshop over August 9 - 25, 2014.
|Clay shaft being built up on a wicker frame, over a stone base chamber.|
|After drying fire - extensive cracking of the shaft (extraction point to right)|
|Equipment set up, at pre-heat phase.|
|Adding the DD-SSW1 analog|
|Bloom mass at initial extraction. Bottom pull was intended, but top extraction was required.|
|After two initial compaction heats, an attempt to cut the bloom.|
|Final Bloom : 5.2 kg (from 28.3 kg dry ore = 18% yield)|
The following will be of more interest to the archaeologicallly inclined:
|The overall remains from the smelt around the furnace.|
|Broken pieces of the furnace, clearly showing the imprint of the wicker interior frame.|
|Furnace opened along the major cracks, showing the slag bowl in place below the tuyere entrance.|
|Main slag bowl removed as two pieces. The tuyere was to the left.|
|Cleaned surface of the rock base. Tuyere was to the top.|
There will be a fuller report to come on making a comparison between the results here, and the remains seen in the archaeology from Culduthel.
Some General Conclusions:
- Some modifications to the layout and construction of the furnace may be necessary to :
- avoid cracking
- conform more closely to the slag pattern at Culduthel
- The analog used proved quite successful, even if the yield was a bit low.
- The general progress of the smelt followed the expected pattern.
- A better system needs to be established for re-heating the bloom for consollodation.