Sometimes a Great Notion (Icelandic Furnaces)

Q : 'Can the Hals Icelandic furnace build be re-used after three winters of weathering?

Well - kind of...

In consideration of the upcoming November 3 (Sunday) bloomery iron smelt at Wareham, Neil Peterson and I decided to return to the 2021 furnace that was a full build of the sod cone with thin clay lining as used at Hals, Iceland. This furnace had suffered considerble damage from both the extraction process and the intervention of a snapping turtle (!) after the June smelt that year. The front section was repaired and it was fired again in September. At that point major cracking resulted in the failure of the front wall section, with a wide band of loosely fused dirt in that area. (see https://warehamforgeblog.blogspot.com/2021/09/replacements-and-improvements-smelter.html )

The structure has been exposed to the weather since that point. Rain had washed loose earth into the interior and out the open front, and caused the supporting sods to slump down. Freeze and thaw had eroded the upper portions of the fused clay liner, and widened many cracks. The still mainly intact liner had slumped forward through about 25 degrees off vertical.

 The remains of the furnace, wild grasses trimmed off the sod cone. Front extraction side forward

Stick follows the line of the inner furnace surface.

Cracked and flaked away surface of the upper portions visible

Neil Peterson and I attempted to dig it clear of collapsed soil and set it back to vertical yesterday.

Not so much! The fractured liner broke into two larger and a number of smaller pieces 

Broken after our attempt to straighten the liner, the two larger pieces each about 1/4 of the original.
 

Working on the impression that will little clay available, Icelanders would attempt to keep what they had and patch it back together (??) this is what we did. 

The missing front section was replaced with on hand stone blocks, setting a ceramic tube tuyere. The previously used basalt lintel stone was set above this to support the upper blocks. From the tuyere line upwards gaps between the blocks were sealed with fresh clay.

The completed replacement for the front section, now all stone blocks.

As much as possible, remaining pieces of the fused inner liner were patched together, gaps and cracks sealed with fresh clay. The clay used is the Icelandic clay analog mix, based on samples obtained by Michelle Hayure-Smith, and suggested by team member Marcus Burnam (see https://warehamforgeblog.blogspot.com/2021/06/sticking-to-it-clay-mix-for-icelandic.html) A very rough calculation was made of the clay required = about 2.5 litres (as a plastic mix).

Image into the interior, showing the lower rear and left side surfaces. Fresh clay is dark grey.

Two wooden sticks were driven down to help support the wall pieces as they were sealed in with fresh clay. It is expected there will be further cracking between the old and new surfaces as that applied clay dries and shrinks. There should be a second repair made to ensure new cracks are sealed before firing. This was a step not taken between the previous two uses, thought to be why there was a major burn through in that earlier front wall section repair.

A circle of stone blocks was added around the top of the opening to even off the shaft. These supported by additional cut sod. As currently set, the furnace has a roughly oval interior, about 30 cm front to back and 35 cm side to side. Total shaft height is irregular at 55 - 60 cm. The tuyere is set about 15 cm above the dirt base (which could be dug lower). This creates a shaft height of 40 - 45 cm.

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Æelfwyn Makes Enamel

Æelfwyn’s starting point was this image of an Anglo-Saxon brooch.

This was her set-up.

And a couple of fun little videos showing her using the bag bellows and then putting a (different) piece into the fire.

Almost done!

The finished piece once it has cooled.

Æelfwyn said she was having trouble with temperature control, hence the bubbles .  The primary experiment was using Theophilus' technique of gluing the wires down with wheat paste, firing it, then adding the enamel.  He used it for soldering gold wire, but it worked fine for enamel.

Stew

 One of our favourite things to do as a group is eat. This was a stew with onions, beets, parsnips, carrots, lamb and herbs, made in the replica Mastermyr pot that Kettil made.

Here’s what the original looked like:

 It was was 26 cm wide x 13.8 cm tall (handle not shown), found in Mastermyr, Gotland Sweden, and dated to circa 1150*. Source: The Mastermyr Find / Arwidsson & Berg, page 11, 29 - plate 11 / number 19d,

Weaving with an Oseberg-Style Loom

The Oseberg Ship was a rich burial from somewhere between 800 and 834, discovered in the early 1900s in Norway. It is now on display at the Viking Ship Museum in Oslo. Two women were buried in the ship, along with many textile-related items. Among the finds were parts of a loom, tablets, and a tablet-woven band. 

The loom, tablets and band as found in the ship grave.

It 

How the loom would have looked, from the archaeological report (Oseberg Fundet, Vol. II). 

The original was approximately one metre high and two metres long.

Hrobjartr, who normally does our tablet weaving, is unable to work due to a broken arm. We wish him a full recovery before he gets replaced by young Fion, shown here making the band found at Oseberg on a reproduction loom.

Our Camp at “Ribe” is Closed for the Season

DARC had a new place to set up camp for this year’s Labour Day long weekend so we imagined coming to the Viking-Age commercial centre of Ribe (in what is now Denmark) as traders and artisans. Trading was a seasonal activity, but people would come for several months each year. This allowed us to have a “camp” but also produce things rather than just “sell”.  

Ragnar and Kettil ran the bead furnace with the assistance of Fion on the bellows, and visitors were invited to try their hand at making a bead. The furnace broke part-way through thanks to a gust of wind that knocked a pole into it, but they were able to mend it and continue. There were also issues with the charcoal, but once they switched to a different charcoal they did manage to produce a few beads.

Thorgeir turned bowls on his pole lathe.

Jhone worked on her warp-weighted loom when she wasn’t cooking, and several visitors had fun weaving under her supervision. Herr she is chatting with Kadin, who is also a skilled textile worker.

Ælfwyn spent the day making enamelled items.

Auðr mostly puttered around the hearth, making butter, fixing some kitchen tools to be more useful, and making a new wooden spatula.

We have some ideas on how to make our “street” more accessible to visitors while retaining the model of workshops in front of sleeping areas, but overall we were pleased with how it worked.

Nålbinding

It was chilly last night so Kaðlin was wise to spend much of the last two days making herself a new nålbound cap using wool she had dyed and spun herself. She is using a simple loop stitch. The pink comes from madder while the blue is indigo over dyed with weld. While indigo was not found in the Viking Norse areas, chemically it is the same as weld, which was.

Iron

Today I happened to sit through a class on iron by Kettil (Darrell Markewitz).

He talked about sources of iron, the basic processes to extract ore and turn it into iron, softer (easier to work), vs hard (holds an edge but brittle) and how both would be incorporated into things like knives or axes.

He also talked about the quality of iron produced and showed objects to demonstrate how it was used.

The most striking figure for me (Auðr) was the average amount of iron per person in a household: 2 kg. What that meant was you would have a personal knife but not much more. A ship needed around 2000 nails. Your household would likely have an axe, maybe some metal-edged farming implements, a cooking pot, and possibly  a bit more stuff like a cauldron hangar, pan or fork, depending on the size of the household. Things like fry pans and forks may have had wooden handles. A shovel would be wood with just a metal edge on the digging part.

Darrell has literally tons of experience making iron. 

2,500 kg of ore used

Just under 5,000 kg of charcoal

81 blooms totalling over 475 kg of iron

72 furnaces (some of which were reused for more than one smelt)

95 smelts

36 different kinds of ore

20 different kinds of furnaces to explore different styles and techniques based archeological remains

16 different kinds of air sources

He has a book coming out later this year to document his 25 years of historical iron smelting and what we expect to be over 100 smelts by the time of publication. Until then, you might be interested in one of his other books:

 

• Turf to Tools
  
• How Dense Are You?