Saturday, August 03, 2019

Viking Age iron smelting air systems?

Those following me may be aware that I am participating in the Hurstwic 'Firing Up Ancient Secrets' project, set for August 23 - Sept 5 at Eiríksstaðir in Iceland.
My contribution is both my research into Viking Age iron smelting methods, and my (considerable) experience with an experimental archaeology approach towards understanding those systems. 
I have been doing a lot of background research and pondering about everything related to bloomery iron making during the Viking Age of late * 
The following is modified from a recent communication with a fellow experimental researcher:



Air systems are especially an area of investigation for me.
What I see as the problem is this:
- We can make blooms that almost exactly resemble the ones found in the archaeology. (Understanding there are not that many samples that have been found.) But to do this requires the application of large volumes of air, and high burn rates. (This based on the pioneering work of Lee Sauder from Virginia  )
- There is almost no hard evidence on what bellows might have looked like from the Viking Age itself. Two images from the period, no object remains what so ever. (Be very happy to be proven wrong - if anyone reading knows something!) This specifically true for possible iron smelting bellows - for which there are virtually no indications on type or size at all. Possibly some signs of post holes that might be supporting frames?

I note here that you most certainly can get some iron produced with low volumes of air. This has definately been proven many times by those working at European open air museums, using what are 'Early Iron Age' methods.
But I consider the quality of the blooms created a very important indicator in results.

My own reconstructions of the blacksmithing bellows, based on those two illustrations, creates a twin chamber unit which in working tests produces roughly 120 - 160 litres per minute (based on one stroke per second)
If you compare this to the 'ideal' air flow requirements, this is at best 25% of the required volume - if you are expecting to create a dense bloom that resembles the ancient ones. (For the 25 - 30 cm interior diameter most of us are working with, air in the range of 500 - 800 LpM.)

So:
Most of us in the experimental community use all sorts of different measurements - or no measurements at all.
One standard is 'charcoal consumed over time'. Again, there is no consistent way this is reported, I see a lot of European workers using 'kilos per hour'. Here in North America (again thanks to Lee) the standard is 'charge amount per minute'. The ideal is usually quoted at '5 lbs over 6 - 8 minutes' (so make that roughly 2 kg).
Here we more typically are running at closer to an overall 1.8 kg every 10 - 12 minutes (so about 9 - 11 kg / hour) Our blooms are intentionally on the smaller size (normally 30 kg ore to about 5 kg iron).

The questions are :
What is the air volume produced by the various *theoretical* Norse type iron smelting bellows?

Ideally, to get any kind of understanding of this, individual teams need to undertake some sort of measurements.
- What are the physical dimensions of the bellows unit being used?
- What is the stroke count per minute?
- Is the actual production volume (when hooked into a working furnace) measured?

- What are the physical measurements of the furnace (especially the interior diameter at tuyere)?
- What is the average burn rate over the smelt?

- What is the yield?
- What is the quality of the iron produced?
(This last is so dependent on the quality of the ore being used - it may not prove a really valuable comparison!)




Right now I am working with a group attempting to experiment with a possible Icelandic based system. At present they are intending to build a large, single chamber bellows (more or less like one half of the known Norse type). This has been tested all of once - and I think is not the way to proceed into the Iceland side of the project.

There may be some element of just how the air flows into the furnace?
- A Norse twin chamber (larger smelting size) produces a flow that never stops, but with changes in volume as each chamber is pushed. The delivery pressure can also be modified each stroke by the force of the push. (Consistency a problem). Requires 3 - 4 workers.
Possible Norse Smelting Bellows - Vinland 3
- Multiple Norse twin chamber, small blacksmith size, linked to a central air bladder. The flow never stops, pressure modified by a weight on the bladder. We have tested this system out twice, but the main draw back is the larger number of workers required (6 - 8).
Blacksmith's bellows linked by bladder - SCA 50
- The single chamber being considered by Hurstwic has no historical examples (that I am aware of). It will produce air that starts and stops on each stroke. Pressure can be modified by the force of the push. (Consistency a problem) Requires 3 - 4 workers.

- A 'great bellows' (two stacked chambers, 'double action') is Medieval at best. This will provide a fairly constant blast, pressure consistent (modified by weight on the top delivery side chamber).  I see a lot of people using this post 1300 system  - and calling it Viking Age. Requires 3 - 4 workers
Settlement Era Great Bellows - Williamsburg
- Obviously use of a modern electric blower gives a constant blast (volume and pressure). Solves the labour problem!


Another extremely important element - which will effect the entire design of the furnaces, is the tuyere system itself. (To be discussed in a further posting)


* If regular readers have noticed a sharp decline in postings here over the last two months - this is the primary reason. 
- June was DARC's major demonstration at Upper Canada Village, plus my presentation at the ALHFAM conference.
- July marked a major construction project (upper deck structure and roofing) at Wareham
- August? 
* formal paper based on the ALHAM presentation to be written
* detailed research into iron smelting in Norway and Iceland
* writing a report relating that research to the Firing Secrets project
* preparing a lecture presentation (before the Canadian Ambassador to Iceland!)
* equipment load out and packing for the trip

Friday, August 02, 2019

BIG 'Can O Worms'


...I would like to open that can of worms again and mention that last week we had some visitors from Germany who appeared in full "costume" at our doors. They had very little interaction with our staff and were rather standoff-ish with everyone. As a matter of fact most thought they might have been "real Indians". They actually made some of our staff uncomfortable, especially our own Indigenous staff as the attire showed a lot of skin as it were. Period correct yes, well done yes. Cultural appropriation? What would you do? How would you approach this. I watched and observed knowing that this is quite common in Europe. After some searches on the internet I found that in Germany alone there are some 40,000 people who belong to these "clubs" and spend weekends at a time in encampments or even longer. There seems to be differing opinions from Indigenous folk north and south of the border. Some think its ok some hate the idea.
Any one out there who may add a few worms to this can?

Yours in History
Del 

That message recently started some conversation on the ALHFAM discussion list. *

The following is (slightly edited) from my open reply.
Presented in the spirit of honest discussion.


Boy - Can O Worms hardly scratches this.
... I am going to ask for any First Nation's members reading to be patient, and try to pull back from their own personal frame of reference.





Correctly identifying Staff in any situation is a problem. Who speaks with authority?
In a classic 'stuff' museum, staff get identified through standard dress (uniform), or at least specific name badges. In our living history sites, historic clothes are the identifier. The visitor accepts information provided by those perceived to be staff. (For those working 'pioneer' periods : What happens when Mennonite or Amish visitors show up at your site?)

But spin this out a bit folks.
One very extreme situation provided in the discussion was people showing up to an American 'conflict' related site - with their 'period' firearms in their hands! This obviously represents huge problems in controlling behavior, especially public safety! (Honestly, I could only see this happening in the USA - with firearms. I have seen, any number of times, costumed visitors to Medieval Festivals waving swords around.)
I would bet many of us here have had the situation where they have visited another site (in street clothes) - and intentional or not, end up 'interpreting'. When you are passionate about history, about sharing information, it is hard to hear a question asked when there are no staff around - and not answer it. I wonder sometimes if I have a big (invisible to me) letter I tattooed on my forehead. (I was at the Yorvic Viking Centre, visiting from Canada in street clothes, and had a teacher ask me to explain a set of artifacts to her school group one time ??)
In the discussion following, a number of suggestions were given about how to differentiate between staff and costumed visitors. Honestly, I think the suggestions that shift into some kind of shaming are counter productive. (Issuing bright coloured sashes one suggestion for example). Consider how 'visitors' are signified at government buildings or in industry. I would suggest a stick on label or a lanyard with badge are typical - and this would be inexpensive. Most importantly this would be seen as a 'standard' approach by the individuals (and other visitors as well).


A second element here is about 'bad history'.
Every institution is attempting to control the quality of information, through some level of staff training, a pre-determined standard story. I'm sure we are all well aware of the 'set piece' delivery : "Welcome to the Irish Cabin, representing 1850..." (heard by myself, on Monday at a local museum).
So I would suggest one of the problems with visitors in costume is that the site can loose control of the information flow. Again, I bet many reading have been in the situation where we have heard poor, or outright incorrect, staff delivery at some other museum. How to contribute / correct needs to be handled with great care - but I'd also bet many of us have attempted this. (Honestly - it goes with the profession!)

The big can o worms is : 'Who speaks for the Dead'

'White Indians' : Interpreters at Jamestown Settlement (about 1998)
I state this in that manor quite deliberately. I am not attempting to be offensive. First Nations have real, ongoing, special, reasons to be more than normally sensitive to this specific example. The original situation described outlines first the problems of staff identification, then further, potential 'bad history'. There is this major third problem laid on top to consider.
Being honest - in truth almost * all * of us working as living history interpreters are representing things we are not. I expect no one reading was born before the Great Depression, likely very few before WW 2. We attempt to represent *history*.

I wanted to point this out specifically, because I personally undertake illustrating the Viking Age. This is in effect a 'dead' cultural set. I am Canadian by birth and culture, not even any Scandinavian lines. Am I allowed? By definition my activities are 'cultural appropriation'. This is fine because there are no living community to complain? Who decides on the accuracy of my portrayal?

'Famous Viking' : at L'Anse aux Meadows NHSC - 1996
I most certainly have experienced the 'furry Barbarian' visitor show up at our historic encampments. Good news for us is that these folks, although perhaps enthusiastic, so clearly do not visually resemble our working interpreters that no other visitors were confused. We had a group of 'O∂inist' (White Supremacist) followers show up at one presentation. They left disgruntled, largely because we were 'too boring', ie did not support their distorted views on extreme religion, slavery, and White Dominance.

In the case given that sparked this commentary, Germans especially have a long recent history of 'Native Re-creation', going back at least into the later 1800's. This has represented a true interest, with all the honest distortions possible when anyone attempts to re-create something not of their own birth - and so far removed from their own life experience.

Does any one cultural group 'own' that material culture?


* " The Association for Living History, Farm and Agricultural Museums (ALHFAM) is the organization for those involved in living history including living historical farms, agricultural museums, outdoor museums of history and folklife and those museums - large and small - that use "living history" programming. "
 

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

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