Tuesday, June 05, 2012

Hals - from Iceland

A fast look at a smelt mounted (Saturday June 2) by Margrét Hrönn Hallmundsdóttir working as part of the Greenvilliage Grampus project (that's a Facebook link, sorry)

Margrét had been in conversation with Kevin Smith about his work excavating an 'industrial' level Viking Age iron smelting site at Hals in Iceland. The DARC team have also been working with Kevin towards a possible full reconstruction of the Hals / Icelandic working system.  Our 5th smelt in that series (interrupted for Vinland) was May 28. Over the last week a conversation in depth between the three of us has been going on.

Margrét should be extremely pleased with her team's results.
On their very first smelt, they got a roughly 3 kg bloom!

The images bellow have been scammed outright from her Facebook postings over the last week.
Consider the commentary a bit vague, as I am mainly pulling conclusions only from what I see in the images!

The base of the furnace under construction. Stone blocks defining a 'slag room', tap arch and grooved support for the tuyere. This marks one departure from Hals, where only small stones have been found, the construction is entirely turf slabs.

A close up of the tap arch and lintel stone. The rock is volcanic - Basalt with many small air voids.

Above the stone, grass covered turf (peat) is laid in flat slabs. A central cylindrical hole continues the line of the stone blocks. This hole is lined with about 3 cm of a mix of 1/3 hot spring clay, 1/3 sand, 1/3 shredded horse manure. At Hals the turf is laid to build a cone (so at 45 degrees).
An overview of the competed furnace, showing the air systems. The tuyere used was a length of standard Schedule 40 steel pipe. There is no specific evidence at Hals to suggest what kind of tuyere was used. Two air systems are in place. A medium volume, low pressure blacksmith's blower (circa 1880 +) and a small great bellows type (post about 1300)

Better view of the bellows. The small size suggests lower air volumes available. This type of bellows will allow a skilled operator to modify air pressure however (so blast penetration into the furnace interior).
Part way through the smelt (?) A nice looking slag tap. You can see that the initial block of turf that had sealed the tap arch has been removed, exposing the bottom of the slag bowl. Although its hard to tell from a photo, the thin tracery of cooling slag suggests a fluid 'happy slag' at this point.
At the top of the furnace, likely about the start of the burn down phase. The ore had looked to be fairly powdery, you can see the lightest fragments have been blown back out of the furnace mouth by the air blast. The original clay lining of the furnace has completely cracked away and fallen into the base. (Suggesting extra slag production). The central cylinder is still more or less in shape, and the wide turf slabs do appear to be containing the reaction gasses.

The extracted bloom under initial compaction. The darker material on the outside is slag, but the still bright core indicates the presence of iron!
The final bloom pieces? (No description with the image) Its hard to tell quality from an image. The shape and surface texture does suggest a lacy consistency, to be expected with the air systems used.

Just for comparison, remember the DARC team did not get any iron at all until our *sixth* smelt attempt.

Great work!!

No comments:


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

COPYRIGHT NOTICE - All posted text and images @ Darrell Markewitz.
No duplication, in whole or in part, is permitted without the author's expressed written permission.
For a detailed copyright statement : go HERE