Tuesday, February 18, 2020

Smelting with Haematite ??

Some comments from a recent e-mail message (edited and extended) :
I am David Watson of Moorforge Viking Settlement... (1)
I took a fast hunt for the Moorforge Viking Settlement web site.
This looks to be a private venture?
Nice work on the two buildings. I've got to admit that I had vague ideas years back of attempting something similar here at Wareham, but never proceeded with it. I've got a serious problem with lack of suitable building materials (and lack of labour / machinery). My place is only a single acre, so resource gathering is not possible / restricted / expensive.
(I do have the basics of a small plank walled 'town house' from a museum exhibit I built years ago in storage. (2) Maybe *this* year I will get the thing set up in the yard? My partner has dreams of a small Celtic Iron Age round house...)

I will be running an iron smelt over the weekend of 14th - 15th March and wondered if you could offer any advice to a newbie if I explain what I have.
First thing :
Do check the files section on Facebook 'Iron Smelters of the World'. I put up a simple guide (based on a journal article) that covers most of the basics of building and running a 'short shaft' furnace. This is close enough to some of the Norse types, clay construction most typical in Denmark. Remember that you need to stick pretty close to the model (changing more than a couple of the variables will seriously impact results).

I have organised an ample supply of hardwood charcoal from a local charcoal burner and have found a local source of clay from a friends woodland, I'm happy with the quality of the clay as it has been used by a potter for fired earthenware,
We have found here that although the clay does impact on slag generation particularly, with some care in building / simple modifications, most clays seem to work, especially if you consider the furnace more or less limited use. A lower fire point / melting point clay will suffer more erosion, typically in an offset oval pattern around the tuyere (10 cm below and side to side, 15 cm above). We worked with a local very low fire red earthenware for our first attempts here. As things like tuyere angle proved to be completely wrong - it is hard to say if the problems we had with burn through of the walls was due to the clay, or the design. We gave up using the stuff because of the labour involved (digging, hauling, breaking, screening, re-hydrating) against the low cost of a dry potters clay (was only $15 a bag!)
If you check Lee Sauder's descriptions, you can see he and I have taken two different approaches to clay mixes.
Lee uses a mix in the range of 50 / 50 course sand to clay. When combined with a lot of care in the build, (and Lee's methods) this results in a fairly durable furnace.
We have worked with a number of clay cobb mixes, settling on clay / sand / horse manure in equal volumes. Horse manure is last years dry pucks, shredded between your hands to the fibres. This gives a furnace that resists cracking, and allows for less attention during the build. The normal here is to build new furnaces (new experimental tests), the most we have used one build for was five smelts.

this leaves me with my ore.
I have about 30kg of haematite from a local mine - the Florence Mine in Egromont Cumbria UK if you would like to look - they supplied the local steel industry for many years but have now sadly closed, the mine is now a museum and arts centre.
The manager is an old guy who worked there when it was active and he tells me the ore is running at about 50% purity and is of very high quality.
Ok - I did attempt a real quick look for details of the Florence Mine on the internet
From what I could gather (??) this appears to be 'Specularite' (warning - I most certainly am NOT an ore geek!)

One thing that jumps out at me : Your local information states ' 50% pure'. Is that rock to haematite? At 50% Fe2O3, your actual iron content is actually closer to 34%. (3)  This may prove too low for effective bloomery smelting.
Is the source material partially purified from the rock matrix?
He might mean 50% iron ?? In which case you should be good. (I guess a test will tell). Expect a lot of slag to tap off!

The ore is non magnetic and the batch I have has been ground to a grit, the same as they supplied to the local furnaces.
At one point I was able to easily acquire haematite used commercially as a sand blasting grit. (4) This stuff was roughly 98% Fe2O3!
A good set of examples of the use of this material was at Smeltfest in 2006
Generally we found that the small particle size of the blasting grit (like a course sand) tended to easily convert to high carbon cast iron. You had to be real careful with your air volume to burn rates, if you got too quick / hot, the cast iron was the result.  The good news is that with some care, the blooms tended to higher carbon contents. Harder to forge into working bars, but certainly a metal more suited to blade making.

If you can offer any thoughts or tips that may help I would be most graitfull, one question I have, will I need to roast the ore before use ?
Ok - this is my personal take on ore roasting :
Why do you do this?
a) If you are working with a rock ore from source, the high temperature fracture the stone, and makes it much, much easier to break down into the required finer pieces.
b) Also with a rock ore, the heat converts the iron oxides into Fe304. This has a darker colour, which makes sorting out the stone matrix bits by eye a lot easier. This also makes the iron component magnetic, allowing for possible magnetic sorting as well (not always the most effective - but as you noted, the Fe2O3 is not magnetic at all.)
c) If you are using a primary bog ore (or any of the secondary bog ore forms), the roasting process will drive off possible sulphur contamination.
I've seen a lot of people yak on about the 'increased efficiency' of converting the ore to the higher iron form of oxide as a first step. There is actually so much waste heat in a normal bloomery furnace, making sure you have the correct stack height (even adding an extra 10 cm) is so much easier than undertaking a separate fire sequence. (I say this noting that I rarely have been able to work with a primary bog ore here - there is none in my region.) We certainly did roast the Virginia Limonite ore I was at one point hauling back from Lee's place from Smeltfest.

So as you mention the ore you have has already been mechanically processed into grit, I don't really think roasting is going to need to be undertaken.

One thing that occurs to me?
As you illustrated a Viking Age context for your work site, what are you going to use for air?
I've done a lot of experimental work related to Norse air equipment. Here I would suggest looking to this blog and doing some searches (there will be at least a dozen commentaries on this topic).
You might also check the work of Michael Nissen from Denmark (who was at the Ribe Viking Centre).

Note to Readers :
If David returns with any more details about his scheduled iron smelt on March 14 / 15, I will most certainly share any information here.

1) Normally my policy here is not to name individuals who contact me, when I convert my return message into a blog post (which often does happen here). As David is openly named and described on the Moorforge web site already, I have taken the liberty to consider him a 'semi public' figure (like I am).

2) World of the Norse : Prepared for the Cranbrooke Institute of Science in 2003, to accompany it's presentation of 'Full Circle - First Contact' (which I also had worked on). 
3) ... and I'm so not a math geek either. 
Atomic weight of Fe = 56, of oxygen = 16, of Fe2O3 = 154
% of iron in Fe203 = 68%
If ore is 50% of Fe2O3, that means only 34% iron
Our own experience here has been that much below 45% iron content to your ore, the limits of the direct bloomery process make any kind of reasonable result unlikely. Ideally you should be aiming for closer to 60% iron content for good results. 

4) At one point available in 40 kg sacks from Opa Minerals, relatively close by at Watertown, Ont. The material was haematite from Quebec, and quite economical at the time at roughly $20 per sack. Unfortunately, the company changed to selling only in metric ton cubes.

Monday, February 17, 2020

CAMELOT Medieval Conference : Call for Papers

Come to Camelot

The Conference on Archaeology, the Medieval and Experiential Learning of Tomorrow
Sunday, September 20, 2020
St Jerome’s University in the University of Waterloo

Call for Presentations, Papers, Workshops, Seminars, Events & Vendors!

This year, CAMELOT invites you to join us for a day devoted to the consideration of “Conflict and Cooperation, Space and Material Culture in the Middle Ages.”

The medieval world operated largely on the reciprocal relationship between conflict and cooperation, between individuals, groups and nations, all of which navigated an ever-changing landscape.  Military, social, environmental, political, and economic conflict were surprisingly often resolved through acts of cooperation.  Space, in architecture, urban planning, and agricultural, as well as imagined spaces (as in mythical places, literary settings and theological contexts), allowed individuals and groups to address these changes.  The result of conflicts often had immediate and important impacts on the material culture of the time.

We invite any interested parties to submit ideas for spoken presentations or demonstrations related to any aspect of medieval conflict, cooperation, space and / or material culture.  Topics for presentation may include, for example:

Ø  Military activities, conflict and cooperation
Ø  Environmental change and conflict
Ø  Political, social and economic issues
Ø  Vendor presentations on material culture including:
o   Blacksmithing
o   Ironwork
o   Heraldry
o   Food
o   Social Customs
o   Clothing
o   Games
o   Entertainment
o   Books and literature
o   Other
Ø  Architecture and building
Ø  Any medieval topic which excites and informs

We invite proposals from undergraduate and graduate students, members of the broader public, enthusiasts, re-enactors, artisans, craftspeople, experimental archaeologists and subject experts.  In short, everyone is welcome and encouraged to submit proposals. The aim of the conference is to educate, entertain and engage with a wide spectrum of interested presenters and topics.

To submit a proposal, please include the speaker’s or vendor’s name or names, title or topic, a brief 150 word abstract and full contact information (including mailing address, phone and email).

Email your proposals in DOC, RTF or PDF format to the conference organizer:

Jamie Zettle at Jamie.zettle@uwaterloo.ca

Deadline for submission:  August 30, 2020

My current plans are to attend the Woodford Furnace Festival (Ireland) and a return to the Scottish Sculpture Workshop for the completion of the Turf to Tools project. This will have me returning to Wareham likely September 18. 

Wednesday, February 12, 2020

Purchasing a Cook Pot

From a recent conversation to a potential customer :
On 2020-02-09 12:50 PM, D L wrote:
We are looking to acquire Viking cookware such as an Oseberg cauldron or say 7L or so.
from the original excavation report (cooking tools seen to right)
The Oseberg Burial cooking tools, with the pot set on the tripod
I think it goes without saying that because of the popularity of certain recent television programs, there has been a massive increase in items available that brand themselves as 'Viking'(1). Many (if not most) of which have only the vaguest reflection of actual Norse artifacts (not that I might have an opinion here!). For me, the mere use of 'Viking' as the descriptor in advertising (as opposed to either 'Viking Age', or more correctly 'Norse') from a supplier is a clear warning bell. There is also a considerable amount of lower quality gear being now produced in India - and as with all things, you get what you pay for.
I have seen a few options coming from the UK that vary greatly in price and often state that they are not food grade.
We definitely want to cook in them. What do you mean by « oatmeal sealed ». Is this a process that would effectively seam the seams to allow for cooking?
Ok - those pieces of information are important - and I am going to unpack the pieces:

On Viking Age Cookware: 
Interpretation based on Bengstarvet, Sweden, in mild steel.
There are two general materials used for cooking pot construction during the period : Wrought Iron / Copper Alloy

- Actual Wrought Iron is only available as an antique material in the modern world. I have only been able to secure the actual metal  in suitable sheet form * once * in my 40 years of making replicas and reproductions :
- So what everyone is * really * using is modern mild steel sheet. Functionally, it really does not make that much difference on the cooking (or dying) side. Note however, that historic objects are made of far thicker metal than is seen in modern replicas. Thickness on VA pots is closer to 4 - 6 mm. Modern interpretations vary considerably, but most typically will be 1 mm (or less!)
- Many suppliers, however, are pushing * cast * iron objects, which were completely unknown in Europe until about 1600.
- A third related material would be stainless steel
(completely modern / post 1900), Our modern nickle alloy stainless steels which will never take the same colour as forged steel / iron.

'Copper Alloy' in Norse artifact terms is bronze, an alloy of primarily copper, with various other elements added in the mix. (It is this wide variation of elements and proportions that resulted in the shift of description in archaeology, starting in the 1980's) Actual bronze (high copper with tin) is difficult to acquire as sheet (in small quantities, here in Ontario at least). So a common substitute is brass (lower copper with zinc).
I have also made a number of pots (based on the artifact from Mastermyr) out of sheet copper.

Reproduction of the Mastermyr Pot - rendered in sheet copper.

Food Safe ?

So - again we go back to the materials, with implications from the construction methods.
Iron pots in the Viking Age are almost all made of many smaller segments, riveted together. There are two general patterns, either a cylinder with a slightly dished bottom, or a number of curved segments creating a sphere (think of orange segments). These seams are hammered close - but are not water tight.  The method of sealing the seams tight is to cook something especially thick and goopy (oatmeal a common choice)  and let this leak into and burn on to the seams. Then you never clean the outside of the pot.
Technically, this method would not be considered 'food safe' to modern health standards.

Exterior of a wrought iron reproduction pot, showing baked in oatmeal as sealant.
Note that using a forged steel (iron) pot has a tendency to darken the colour of food, this is only cosmetic, not a food safety problem.

It is possible to 'fake' the look of the correct construction by taking a commercial 'spun' pot or form, then hammering in lines (to suggest seams) and lines of tight rivets. This leaves you with an object that would look fine from say about 2 m distance. Also easy to perfectly scour clean the inside. Typically the spinning process requires quite thin metal however.
I have done this in past using stainless steel mixing bowls as the forms - it would represent a low cost alternative.

With copper alloys, both the cylinder and segmented construction have artifact samples. One other construction method is to 'finger overlap' seam edges (used in the Mastermyr sample seen above). Copper alloys can be soldered water tight.
- The potential problem with high copper alloys is that the green oxide formed (if allowed to sit for a long time without cleaning!) is poisonous. One possible solution to this is to 'tin' the interior surface. This method is seen in much later time periods, but little evidence is found on actual VA artifacts. Easy solution here is just to * clean your gear * after use!
- This all raises the most common problem with modern 'replicas', most especially those cheap end versions from the Middle East or India. Use of lead based solders, the lead being quite toxic! 

I would strongly recommend NOT cooking in any soldered seam pot that does not  specifically  list the use of modern 'lead free' (tin) solders.

I can report that DARC has used actual wrought iron and mild steel pots with oatmeal sealing, copper / brass pots with lead free solder joints - all for decades now in regular presentations. On a number of occasions for as long as two week periods. Never with a problem with food safety.

As to the thickness, I would have to default to your expertise.
Generally, modern industry is able to create much thinner sheets than available during the Viking Age. Although heavier sheet is available, it requires considerably more work effort to form (and big cost increases as raw materials - especially with high copper alloys).
The balance here is controlling cooking process over an open fire. Generally the thicker walls mean more even cooking. This is especially a problem with the thin stainless spun bowls I mention above. These work great for 'wet' cooking (like soups), but make it hard to control burning the bottom with thick stuff like stews.
I have a good supply of 1/8 thick mild steel (so 3 mm) sheet, if looking at one of the segmented iron types.
Note that copper is considerably more expensive as a raw material.
I currently have a full sheet of actual sheet bronze of suitable thickness (about 1.5 mm) on hand (chance find!)

As for an exact replicas, we are not an actual museum but we aspire to learn, to share and to be become as close to historical as we can given our means.
There are some general outlines on costing on the 'Norse Replicas' part of the Wareham Forge web site. Any specific object needs to be quoted individually.  As you can see there are a lot of variables depending on details.

Oh - one other thing. I've replicated the Oseberg Tripod a number of times - and much as I would like to sell anyone reading a reproduction :
This is an extremely problematic object - and most likely was NEVER an actual cooking tool.
The most accurate would be a simple wood pole tripod!  

Oseberg Tripod - My Interpretation
Tripods in the Viking Age - again

Norse cookware created for the feature film Outlander, in 2006. Also included a cauldron hanger and cauldron, and a 'slave chain'. The chain and the cauldron set are both clearly seen in the final film.

All the replicas seen here : by the Wareham Forge
 1) On a three minute search on the internet found a typical example : 'Viking Shield
- You will see on the 'about us' that there is absolutely no information what so ever about sources of the objects offered. 'In Business since 2000' does not inform you in any way what so ever about research, accuracy, materials, ...
Check the offerings listed as 'Feasting'. NOT ONE of those objects is based on ANY known Viking Age artifacts. Description of materials is in fact INCORRECT
Fantasy designs, poor descriptions, lack of quality - and yes, cheap pricing = objects bulk purchased from India. 
Hot Links deliberately avoided. 

Monday, February 10, 2020

Experiencing the Viking Age!


Experiencing the Viking Age
August 1 and 2
( Saturday, overnight and Sunday)
Requires TWO confirmed bookings
be a viking

You have seen it on the television shows and movies - but what was it ACTUALLY like to live in the Viking Age?

This is an intensive two day and overnight immersion into the daily life during the Viking Age :
- a starting lecture segment on 'material culture' (objects and life)
- wear period clothes (provided)
- setting up your camp (replica tents and gear)
- preparing an evening meal ('cold food' as lunches - all provided)
- sleeping out in the tents (with suitable bedding)

Once camp is established, undertake a number of Norse handicrafts
- pewter casting in soapstone moulds
- glass bead making
Each resulting in objects you take home to keep!

Participation limited to FOUR individuals.
Children accompanied by parents welcome (8 years or older please)
Course fee of $450 (+HST) all materials.

For more details on this special program : Experience Viking Age

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

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