Monday, March 28, 2011

'Harper Government' falls...

...while I'm out of the country at Smeltfest.

Friday, March 25, 2011

Heat under AFRICA

This is the third of my short overviews of the activites at Smeltfest with other members of the North American Iron Undergound. Note to readers : I’m reporting on events several days in the past at this point.

Work on Tuesday started with preparing the large African prototype furnace for firing.

This is the interior of the furnace, showing the set of the individual tuyeres, with four set in each of the four arch quadrants. The slag pit below the furnace has been filled with short lengths of green branches, each about 15 inched long.
This is the same shot, with the bed of the furnace established. A thin mat of broken straw covers over the stick ends, topped with a thin layer (about 1 cm) of charcoal fines. Its fully expected that the ignited charcoal will establish its own working level. The layers seen function to keep smaller pieces of burning charcoal from falling straight down between the sticks into the pit.*At this point the first layer of clay tuyeres have been installed into the open arch. The initial spit wood fire has been started. Next the remaining gap will be filled with a loose high sand and rough clay mix to seal the base of the furnace completely.
At that point, the furnace was charged with small pieces of dry wood. About enoung to fill a standard garbage pail had been pre-split into roughly 1 x 1 x 10 - 15 cm long splits. On top of that material was added larger flat pieces mostly the same length.perhaps twice again as much material.

The heat created operated the furnace like a big charcoal retort at this phase, resulting in considerable smoke from the stack. This certainly indicated that the tuyeres were in fact drawing enough air to produce a significant natural draft. Jeff figured it was more than time enough to ignited the exhaust gasses, touching these off with burning paper at the lower charge door. The effect was quite dramatic...(The handle for this can be seen in the bottom of the pipe in the image above.)

Once that wood fuel was obviously fully ignited, rough charcoal was added to fill the lower chamber. Of course some of the wood had burned away by that point. It took about two 40 lb sacks of charcoal to fill to the ‘neck’ where the shaft starts. Jake Keen, the smelt master for this experiment, is seen adding charcoal via the charge door in the image above
The charging cycle of 5 lbs of charcoal and 5 lbs of roasted and crushed Lexington rock ore was started almost imediately after.
The furnace would settle down to a fairly uniform consumption rate of 5 ore plus 5 charcoal roughly every 10 - 15 minutes. Of course there would be variations on this! Twice the furnace almost stalled out, with internal temperatures obviously dropping and consumption greatly increasing. With a total of 200 lbs of prepared ore on hand, many long hours of furnace tending were expected. The initial fire had started about 2 pm on Tuesday, it was fully expected to take 24 - 36 hours to run the complete smelting cycle.
One effect that came to be relied on is seen above. As each individual charge was fully ignited inside the furnace, the stainless steel stack pipe would start to glow a dull orange to red along its whole length. (The image above is hand held at about a half second exposure.)

I personally ran out of juice by about midnight Tuesday. I set my alarm for 4 AM and grabbed some sleep. Various others retired at other points. When I got back to the site. Jesus Hernandez, Dick Sargent, Lee Sauder and of course Jake Keen where the only ones still functioning.
The last charge was made about 5:30 AM, so roughly 14 1/2 hours after starting. It was agreed that many hours would be still be required until the ore already involved would burn down to tuyere level. We all went back (or to!) bed....

(next entry : opening the furnace)

Tuesday, March 22, 2011

SMELTFEST 11 - African part 2

This is the second report on doings at the annual SMELTFEST intensive at Lee Sauder's shop in Lexington Virginia.

Work has been progressing on the African prototype passive draw smelting furnace:

This is the furnace, part way through Jake Keen 'tarting it up'. The core structure here is seen as the gray colour clay. This is straw cobb, about 5 - 4 inches thick laid over a withy framework (see the last post). Next a cushion of straw, roughly 2 inches thick was applied. On top of that is a second clay layer, this dug straight out of the back behind Lee's workshop. Jake plans to extend this covering over the entire structural surface. The extraction slot I laboriously dug into the (mainly rock!) soil has been back filled with loose soil and small gravel (where Jake is kneeling).

Jake is seen here checking one of the clay tuyeres he has been making for rough fit. The plan is to have 16 of these, four for each of the quadrant arches. At this point the exact fit for these has not been established. Likely these will have a pronounced down angle, the tips placed close to the centre of the furnace.

As of last night the construction of the furnace is finished, and an increasingly large wood fire had been built in the interior. Later in the evening, the furnace was packed with stove wood pieces, metal plates put over the arches, and left to burn out over night.

Plan for today is to prepare the furnace for the full smelt series, hopefully to start about noon. The big unknown (for me) is if the interior will be cool enough to permit this work. (The interior chamber is just over 24 inches in diameter.) The lower pit is to be filled with vertically standing green sticks, cut to roughly 15 inches long. These will support the initial combustion, then the developing slag bowl. As more and increasingly fluid slag is produced, it will run down into the gaps between the sticks. Eventually the building mass of slag will slowly burn out the tops of the sticks allowing the block to sag into the pit. If all goes as its supposed to (??) this keeps the developing bloom at the ideal placement inside the furnace.

Wish us luck!

Sunday, March 20, 2011

SMELTFEST 11 - initial doings

As some of my closer readers know, I'm away right now at Lee Sauder's shop in Lexington Virginia for the annual gathering of the North American Early Iron Underground. Here's a fast report...

One of several projects and investigations under way is the construction of an African styled passive draw furnace under the direction of Jake Keen*. (Jake seen in the image above.) It is a slag pit furnace, with a long trench off one quadrant, intended to drag out the eventual slag block. The core of the furnace is framed with saplings, we are using sections cut from an old water heater to frame the openings where the clay tuyeres will be inserted. Believe it or not, there are even MORE rocks in the 'soil' here at Geminal Ironworks than the ground in Wareham.

The construction of the furnace is clay cobb, mixed with chopped local plants (a wild variant of broom straw). Jake is inserting a layer of straw between the frame and the applied clay mix. This is to allow the clay to shrink without cracking (we hope) as it dries. My job at this point was applying a further 4 inch layer of clay like soil, another line of straw, then revetting with stone and back filling with earth. This is to support and keep the bottom 18 inches or slow from slumping.

This is the construction of the furnace as it was completed. You can see the dome of the furnace proper extending to the shaft. To speed construction, we have constructed a stainless steel pipe as chimney. A natural draft furnace needs a certain minimum height to create the air flow dynamic. (Our combined brains are a bit fuzzy on the details here, best guess is at least 6 feet of height is required.) Not seen in this image is a sliding hatch cut in that allows for feeding ore and charcoal at the bottom edge of the pipe. In Africa, likely some kind of scaffold would be used (??) to add new material.

This is a type of furnace that Jake, Lee and Mike McCarthy had seen as ruins in their recent trip to Africa. As partially buried furnaces, the lower construction is a matter of some guess work here. Of course the upper shafts were all erroded off, so the exact working height is unknown as well. Our stainless pipe extends at least 10 feet up, working on the theory that taller is better here.

Today Jake will start a gentle fire in the lower pit, attempting to slowly heat and dry the massive clay walls with out excessive cracking. Also for today will be making all the clay tuyeres. The plan is to start with four tubes for each of the four arches framed by the metal pipe.

* This is the famous ' Are you ... JAKE KEEN?! '

More to come...

Monday, March 14, 2011

Ancient Bronze working?

" I'm trying to process bronze (10%Sn) specimens for my master thesis. I have purchased the adequate metal and my trying to find information regarding forging and annealing (temperature and time) at the roman times."

If you don't mind some practical suggestions? Its hard to tell from your message, but it seems you might be working in a more experimental archaeology method, working modern pieces and comparing them to artifacts?

I have worked with hot hammered bronze bars a few time (not extensively, I admit). You want to bring the metal up to a bright red or maybe to a dull orange colour. Once the temperature drops below a dull red (so you can not see visible colour) you most certainly stop hammering. (Alloy not withstanding)
The key to this is working indoors, or maybe at night. The temperatures with bronze are much more restrictive than with copper or certainly iron. Indoors or night would give you constant light levels in the workshop, so you could learn the best set of visual cues. I mention this quite specifically, as the ancients would not have any other method of judging temperature ranges.
The individual alloy mixes will change your working ranges. Pure copper moves like butter in the red temperatures, but can still be hammered even cold. Bronzes get brittle very quickly (and dramatically) as the temperature drops below visual (again dependent on the exact mix).

For annealing, the copper alloys are heated to a 'dull red' (colour showing) then plunged in plain water. I don't really think you need better control than that. (not in my experience anyway)

The problem relating this to Roman technology may lie on the forges used. Charcoal fires of the time are generally fairly small, so only a smaller portion of a large object could be effectively heated at a time. If my experience with working copper sheet hot is any clue, you would be heating and working only part of a large object (imagine a sheet for a cauldron) at any one time.

Fun stuff to play with! Copper alloys move very fast under the hammer blows. Beware toxic elements (especially copper / zinc brass pretending to be bronze). Historic alloys also contain lead, also extremely un-healthy in the workshop!

I know this is a bit thin!
I'm off to Virginia for two weeks of Smeltfest tomorrow. Present will be Lee Sauder and Skip Williams (the hosts) / Mike McCarthy (I'm driving down with)/ Tim Young and Jake Keen from the UK / Jesus Hernandez and Jeff Pringle (two excellent bladesmiths) / Sheldon Browder and Steve Mankowski from Williamsburg. I am SO looking forward to this. I'll try to post from the madness...

Tuesday, March 08, 2011

I Am (Not Stephen Harper's) Canadian

I Am (Not Stephen Harper's) Canadian
15650 Signatures
Published by Melissa Turtureanu on Mar 03, 2011
Target: Government of Canada
Region: Canada
Tweet this petition:

Background (Preamble):
The current governing party of Canada has issued a directive that reference to "Government of Canada" should be replaced by "Harper Government" in federal communications.

In changing the long-standing terminology "Government of Canada", the current governing party is seeking to equate its leader, Stephen Harper, with the the act of governing this country.

As a democracy, Canada is not run by one individual. It is a country run by an elected body, which is accountable to the people and answerable to the opposition.

In the words of Abraham Lincoln, "Democracy is the government of the people, by the people, for the people."

The government of Canada is not Stephen Harper and Stephen Harper is not the government of Canada.

The government of Canada is the people and the people are the government of Canada.

One collective body, not one man, forms this government and make this country a beautiful place.
We, the undersigned, call on the Government of Canada to cease official reference to itself as the "Harper Government".

This is not just Stephen Harper's government. It is the government of the Canadian people.

Our country is not Stephen Harper's Canada. It is a democratic Canada.

I am not Stephen Harper's Canadian. I am Canadian.

We demand that all official references to the Canadian government continue to use "Government of Canada". Any official reference to "Harper Government" should be immediately ceased.
The I Am (Not Stephen Harper's) Canadian petition to Government of Canada was written by Melissa Turtureanu and is in the category Government at GoPetition. Contact author here.

(Text stolen completely without permission from

Sunday, March 06, 2011

Peterson Fence Project

... or what I did with most of February.

Fence and reason why. / Full scale layout drawing. / Prototype Bracket

The customers have a board and batten fence around the front and down the driveway on their property. With a new (young and energetic!) dog, they are concerned that he will be able to jump the existing fence. There are posts set roughly every 8 feet, the fence boards are cut on a sweeping curve in a sideways D shape. The difference between the peaks in the middle and the level at the posts is about 12 inches.
As a an alternative to replacing all the fence boards, they asked me if I could work up a decorative metal extension in increase the effective 'blocking' height of the fence. My solution was to use a horizontal line of 1 inch diameter pipe, held above the existing fence top by a set of decorative brackets. The intent is to raise the line of the fence by 4 - 6 " at its highest point (so 16 - 18" above the post area.
To fill the gap around the posts will require placing a total of four brackets (using a roughly 6" square grid as the spacing guide). The pipe will consist of a number of 8 foot pieces, with a small gap just above the individual posts. This allows for any sway to the fence line. It will also make installation a lot easier, even allowing to raise the height of the pipe line should that prove necessary.
The individual brackets will be forged to individual organic curves. The top end tapers to a leaf shape, which wraps around the pipe to secure it. The leaves hang down below the top line, helping to block the gap above the posts. I also wanted to enhance the organic feel of the brackets. For that reason I forged a separate smaller 'tail' which will be welded to the main structural part of each bracket.
To ensure there would be enough physical strength to the support, I chose 1 1/2 wide by 1/4 inch thick flat stock. The tails are forged from 3/4 or 1 inch wide by 1/4 (roughly half of each width).

Creating the initial prototype took roughly two hours. You can see the ground areas over the MIG welds. To calculate how much stock would be required, I actually forged the main support from two pieces of known length, then cut and welded to proportion. The finished brackets will be roughly 30 - 32 inches tall.

Each starts with a strip of 40 inch long material. These are the individual forging steps to create *just* the profile - before the forging of the pipe wrap or any of the organic curves. Each of the steps below represents 'one heat' cycle.

- Cut length from 20 foot starting stock
1) Hand forge the corners of rectangular end to round, flatten 'ripple'
2) Air hammer the last 3 inches into a rough point

3) Hand forge this shape smooth and to a sharp point

4) Hand forge the start of the shoulder profile with wide shoulder tool
5) Hand forge to finish the shoulder profile with a spring shoulder tool

6) Air hammer to start taper to bottom of shoulder

7) Air hammer middle portion of taper

8) Air hammer starting portion of taper, start to work back for an even line
9) Hand hammer over completed taper to smooth lines as required
Showing completed group of three *. The bar has increased from 40 inches to roughly 46 inches long.

10) Hand forge the corners of rectangular end to round, flatten 'ripple' (other end of bar)
11) Air hammer end to tapered point (about 6 inches)

12) Air hammer middle segment to extend taper (about 6 inches +)

13) Air hammer top segment to finish taper, start working lines towards tip to even

14) Air hammer middle towards tip, evening taper lines

15) Air hammer to tip, finish evening taper lines, additional hand forging to sharpen point

The starting bar has increased from 40 to roughly 56 inches by the end of initial profiling.
* Now, I found that the ideal arrangement was to have three bars in the forge at any given time. By the time I had worked over three pieces as one step, the first bar I had worked had gotten back up to correct forging temperature. I did use my two burner propane forge for this part of the project:
1) Its winter time, and that's what I use to also heat the forge room
2) These are long straight shapes, ideal for fitting in the limited fire box of the propane forge
3) For production work like this, the gas forge will not overheat the other bars in a series
Normally I would place the next group of three to one side of the forge as I was drawing heat for the last step on the earlier bunch. This pretty much kept me from having too much waiting time before metal was to working temperatures. (In the image above, the door has been opened to take the photo. The door on this forge pivots on the right hand side, making it ideal for this kind of work. There is also a small pass through door on the rear left.)

I found that I could produce a total of NINE pieces as described in roughly THREE hours working time. And that's about all the effective forge time I can manage in a session.

Repeat for a total of 62 pieces!

The work (over the 62 elements) described here represents about 1/3 the total effort required to complete the overall project.

(Thanks to Karen for the image of Thoka at the Fence)


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

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