Wednesday, November 19, 2014

Turf to Tools - ONLINE PRESENTATION

On Thursday the 20th of November, as part of the Being Human festival, the dot.rural SIRA STREAMS project will be holding a public event with Scottish Sculpture Workshop about their 'From Turf to Tools' project.
'From Turf to Tools' is an ongoing enquiry into resources, material and landscape. During August 2014, this led to the recreation of an Iron Age smelting process in Lumsden, Aberdeenshire. Join us for the event online to find out more about the project, see video footage of the smelt, see the materials used and produced, and participate in a live Q&A with artist Eden Jolly and Master Blacksmith Darrell Markewitz (joining us remotely from Ontario, Canada). Hear about work being carried out at the dot.rural Digital Economy Hub to share these activities online with remote audiences worldwide.

The event commences at 6.45pm (UK time) - if you wish to participate online please register here for your invitation:​

http://www.eventbrite.co.uk/e/out-of-the-earth-streaming-turf-to-tools-tickets-14072111063​

Hope to see you there!
Dr. Leanne Townsend
Research Fellow

dot.rural Digital Economy Hub
University of Aberdeen
Kings College

Wednesday, November 12, 2014

Last Chance to See (?) Course

(Sorry for this 'shot gun' approach - let me know if you want OFF the general mailing list! Especially if you have *already* taken this program over 2014.)

Did you miss the scheduled 'Introduction to Blacksmithing' courses this year?
Still interested?

Introduction to Blacksmithing
November 22 & 23

'No Kidding - Absolutely LAST Chance This Year' (maybe?)
Saturday & Sunday, working with gas forge only

This is an 16 hour program that stresses a hands on approach, with two full working days in the forge. Only 4 students per session, each with their own work station, means close personal attention. Projects include poker, 'S' hook, wall hook, and at least one small decorative item (more as time permits!). Course fee of $325 (+HST) includes coffee and materials.

For the full list and descriptions see the web site :
http://www.warehamforge.ca/TRAINING/course.html


Clay & Organics - Furnace Building

 Question from Dan - on Don Fogg's Bladesmith Forum - 'Bloomers & Buttons'

Any advice on smelting furnace materials? Firebrick? Kitty Litter?

As I have mentioned, there is a dance between ore (as the lead) and furnace details. Playing the tune is construction materials on melody and charcoal type sometimes improvising.

Powered potters clay is cheap and very easy to work with - and can be purchased as known types.
Local clay is considerably more work (unless you are one of the lucky ones) and usually will have quite specific (likely unknown) properties.
You can make your own decision if digging, hauling, drying, breaking, cleaning then re-mixing a local clay is worth the roughly $10 - 15 a bag of powdered clay costs.

Working with clay obviously gives you the most flexibility in terms of design. (Making a cylinder using rectangular bricks is sometimes not the easiest.
Remember that the air blast, so the burn pattern, in the furnace will be some variation on a *spherical' volume. You make a square or rectangular furnace and there are going to be corners that are not going to burn / contribute to the reactions. (Japanese Tatara aside, but there the system uses multiple air points to get around the physics.)
Parks Canada / LAM - 2001 (first smelt attempt). You can clearly see that the two corners opposite the tuyere point are not ignited at all.
Like everything else, there is a knack to working with hand mixed clay.
Lee Sauder's  / Owen Bush's  advice of mixing up your clay balls and leaving them to relax is excellent (time / space / manpower allowing)

At this point I don't think any of the successful, multiple smelt workers are using a straight clay (??)

Sand in the mix reduces the way  wall material expands when it heats to operation temperature.
A high sand mix does require considerably more effort on the build. It also requires much more careful drying / baking before the furnace is used.
The result however, with the care needed, is most certainly a more durable furnace.
This is the mix that Lee is using, and he certainly has had an individual furnace re-used dozens of times.
One of Lee's Furnaces (a slightly older version)
Organics added will do three things :
- Pieces remaining in the outer layer of wall act to bind the whole structure together. This action tends to limit potential cracking, and hold the walls together even if cracks form.
- Organics with hollow cross section (ie - straw) allow some place for the expanding steam to go, steam produced when the water in the clay heats. The massive increase in volume as water flashes to steam is the primary source of cracking of the clay walls. (Obviously very careful / long duration drying limits this available water remaining in the walls)
- Pieces remaining in the inner layer of wall will eventually burn away with the high temperatures of an operating furnace. This in effect leaves air spaces, which are insulators. The gross effect is to help limit the loss / spread of heat into the exterior surface of the furnace. (This at least in theory, honestly I doubt anyone has actually tested for this ??)

Obviously differing organic additives will perform differently:
- We tested 'peat moss' - purchased locally as spaugam moss for gardening. The long pieces soaked up excessive water and held it, making mixing a bit of a pain (hard to get consistent mix). Then the drying became a real problem. In the end we got excessive wall cracking - there was just too much water being held by the mix.
I highly expect that what anyone would get locally as 'peat moss' might vary an extreme amount - region to region.
- We have had extremely good results with shredded, dry horse manure. Get last year's pucks, rub them between your palms. What you end up with are very dry lengths of grass, usually about 5 - 10 mm long. Added to clay, these pieces act just like fiberglass bits in car repair 'bondo'. (I learned this technique from Micheal Nissen in Denmark.)
- Our old stand by here is chopped dry straw. Cut the pieces to 5 - 10 cm long with a hatchet or machette. Straw (rather than hay) has the hollow core mentioned above. The net effect is just like adding rebar to concrete. It does make hand mixing a bit of an effort.

Learning from Lee, the normal mix used here at 'Viking Age Central' (Wareham Ontario) is a rough mix by volume :
1/3 powdered clay / 1/3 course sand / 1/3 organic material
Often we will use a higher fire temperature clay (like the EPK suggested) for the part of the furnace around the tuyere level (which suffers the highest temperatures). I have noticed any particular problem mixing different clay types in one furnace.

We are undertaking more experimental archaeology here than production smelting here. For that reason, we are constantly changing details on furnace construction (so building a *lot* of individual furnaces!). To date we have only used one furnace for a total of five smelt events, the average is closer to two smelts per furnace before we build a different model.

After seeing a whole lot of furnaces built, I would suggest the most important factor is :
Take your time and use care in the build - this pays back with less cracking and more durability
The single biggest error people make is not making sure the individual balls / blocks of mixed clay are well fused to each other as you build up the walls. Cracks are almost always along the joint lines of the individual blocks as added.

Darrell
see
www.warehamforge.ca/ironsmelting
for images of a whole lot of differing 'Short Shaft' furnaces

Tuesday, November 04, 2014

'Spears of Summer' - at Elora

... or maybe not so much, as I took the piece down on Sunday after its summer exhibited as part of the Elora Sculpture Project - 2014

See the original proposal as drafted :


The completed sculpture as installed proved extremely difficult to get any good images of! The location was just to the east of the main intersection in Elora, but on the side of the street. This made for complete chaos in the background!

In the end the base was encircled with rough stones - mainly as an extra security measure to prevent the un-wary from walking into the pointed terminals.



'From the Fury of the North'

'Deliver us' (plus maker's mark)

It proved too difficult to use the crimping technique to apply the bottom 'barbs' as originally designed. Instead I welded on the sharp triangles remaining from the starting cuts of the end points.

If anyone viewing might be interested, Spears of Summer is available for purchase. The original asking price is $2500. The piece stands about 7 1/2 feet tall. The metal has intentionally been left with its 'out of the forge' fire scale, which is slowly starting to red oxidize naturally as it weathers.


 

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