Tuesday, December 10, 2013

Knifemaker Interview - Part 2 A

I have to wonder how Dr. Wallace altered her perceptions and what
triggered that that change in her thinking. I've found the relationship
betwen smiths and archaeologists to be fruitful when both are open
minded. Seems that way with you and the folks at L'Anse au Meadows.

Thanks folks. This year has piled a lot of 'personal life' rocks on top of me, and hopefully into 2014 I will be starting to crawl back out from them.

Something Alan said about the interface between the archaeologist and the blacksmith.

Part A - what we got:

The original excavations at L'Anse aux Meadows, back in the 1960's, was a real mess in terms of who was involved and how things were carried out. Anne Stine Ingstad had been trained at university as an archaeologist, but actually at the time of the find was not *working* as an archaeologist. As word of the discovery got out, everyone internationally remotely interested at the time tried to get into the process. (I have seen film clips of 'ivory Tower' types, in suits, ties and dress shoes, being physically carried from small boats to shore on the backs of locals. At the time there was no road access to the site.)
At the very least, no one actually undertaking the first series of excavations had ever worked on a historic iron smelting site. At the time, no one had really undertaken a successful re-creation of a historic iron furnace either. (Near as I have been able to research, the first steps into experimental archaeology there look to be in the mid to late 1980's, and that pretty hit or miss as single attempts. Peter Crew from the UK mounted an extensive series in the early to late 1990's. Our own Sauder and Williams follow in the mid to late 1990's - but approaching from the 'working' direction.)
My friend (and mentor) Dr Birgitta Wallace was working on the original excavations as a graduate student. (So I have managed some inside information.)

One of the base problems with archaeology is that it is a destructive process. Typically you end up removing the very thing you are attempting to study in the process of recording it. So when you combine that with a group of people who don't know exactly what they are really looking at - things get lost or missed.

(I'm going to try to link over to a few images here - see it that works)

So this is what was recorded inside the Furnace Hut at LAM:

This is the remains of a high temperature fire base, indicated by burned charcoal. It is framed by several small stones and a partial ring of baked clay. The ground around it is dotted with primary bog iron ore (to the top right direction) and with small pieces of 'iron smelting slag' (mainly in a line towards the bottom).
The rough interior diameter of the fire base is 20 cm.
The clay crescent found is a mix of a local 'river' clay mixed with sand. (And no, Lee, there is no indication in any of the reports just what the mix might be.) There is a small clay bank exposed about 500 metres from the Furnace Hut. (I do have a small pail of this stuff from our 2012 trip out there, but have not done anything with it yet.)

You can clearly see that no actual structure of an iron smelting furnace itself actually remains. What was the height? Location or type of tuyere? Air system used?

The natural primary bog iron ore is under constant formation along the bog that sweeps upwards from the sea shore location of the occupation site, inland. Black Duck Brook cuts the bog, exposing beds of this ore here and there. The samples of ore from the excavations are quite rich in iron (range of 68 % Fe)

There was no differentiation made in the reports (or notes) for different *kinds* of slags. The total amount of slags (all kinds) recovered was "about 10 kg".
Now it is possible (theoretically) to estimate the yield from an individual iron smelt. You measure the various components of the starting ore. You measure the components in the slag formed. There will be a drop in iron content from the ore to the slag. You multiply the loss by the weight of slag = the 'missing' iron - so the bloom created.
First WAG : A loss factor of 5 kg was added to the amount of slag recovered (???) No actual slag bowl was recovered (The Furnace hut is about 10 feet from the edge of the brook - on the open side.)
Second WAG : Based on the photos (not the best, admittedly) I have seen, there was a quantity of both the green bubbly 'goo slag' as well as the later black liquid (iron rich) tap slag recovered. Only the iron rich slag is useful for the calculation. No separate record of the total amounts appears to have been made.
Running the math gave a WAG x WAG x % estimate of 3 kg for the bloom produced.

The most typical published estimate for the amount of ore used comes from adding the slag recovered, plus that error addition, plus the estimated bloom - to give an amount of 18 kg ore.

No specific consideration was made in any of the reports (confirmed by Birgitta Wallace) for the actual *bloom to bar* phase of the process.  (At this point all fellow blacksmiths will be shaking their heads!)
It has been my personal observation that the remains at LAM are most likely the torn down base of the actual iron furnace, converted into a kind of 'deep dish' forge for heating the bloom to compact it into a working bar.
The 'actual bar to object' phase might not have taken place in the Furnace Hut at all. One of the house buildings has a fire that has traces of iron 'forge scale' around it.

At least one iron object, a nail, was found to have the identical trace element fingerprint as found on the bog ore from this location. This indicates at least that one nail was made from iron produced at LAM.

Also recovered on the overall site:

One of the three building complexes had a side room attached to the main building (indicated by wall foundations). This was open on one end - the end facing the natural beach (as it existed in 1000 AD). Imagine a modern 'car port' on the side of your house. This room also had a side door - opening off into the yard. Found in a spray shape from the interior, fanning out from the door opening were about 100 fragments of iron rivets and their associated rectangular roves (washers). These rivets were used to hold together the planking of a small (to fit the 'garage') boat. This all most certainly represents a large single repair event. The total mass of the combined pieces was : 3 kg.

Three kilo bloom = three kilo rivets & roves

(mull that over a bit, I'll finish this part of the tale later)

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

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