Saturday, July 7, 2012

Continuing to Objects...

Although the Bloom 2 Bar Project is officially completed, I thought I might continue the occasional posting here that would relate directly to the work of the project. 

I really wanted at least *something* new for the Goderich Celtic Festival, and Summerfolk the weekend following (Only three clear days between them, and there is an offload and re-pack in there too.)

The ideal would be to have something as completed objects that represented the three months I spent on the Bloom To Bar project:

Starting billets - bloom iron with spring steel cores
Rough forged blade blanks
I had prepared two billets I intended to lead to a very specific bladesmithing design. The top one is iron from Slag Pit 2 ( # 49 , November 2011 ) an the bottom from Black Rock (# 14, February 2006 ) In both cases the iron was deliberately used before much welding and folding had been done, specifically to allow cracks and irregular edges. I actually had gone a bit *too* far on the Slag Pit 2 iron, ending up with most all the flaws removed. For the second attempt, I was able to restrain my natural desire to forge in all the imperfections.

In the lower image, the two blanks are at different stages in completion.
The top blade has had the blade profile roughed out, and the first pass on forging the edge completed. The hilt is only vaguely shaped at this point however.
The bottom blade is complete in its forging. I had ground the rough forging to the basic lines I wanted for the finished knife. I find it easier to check for warps and wobbles if I do this first. Then the blade was forged again, first to correct any irregularities, second to refine the edge. (Forge thin - grind thinner). It is now ready to be surface ground, then the finished surface to be created on the belt sanders. Then heat treated. Then finish polishing. (The actual forging out of the knife shape is by far the fastest part of the whole process!)

Stay tuned for images of the completed knives...

(Edited from a longer post on Hammered Out Bits.) 

Thursday, May 24, 2012

Forging 'the custard'

 Edited from my ongoing on  Don Fogg's Bladesmithing Forum

Darrel so when you say 'weld in all the edges'... do you mean basically turning it on it's side and hammering down all the little bits at welding heat?   I'm assuming this is easier with lower carbon steel and iron.  On my very high carbon stuff.. those little bits just fall off.  

I would most certainly *not* hold my working methods up as the ideal!

That being said, I'm just coming off a two month research / learning project called 'Bloom to Bar'. So for while there all I was doing in the shop was working up some of my big pile of blooms (!)
So, that being said, take a look at :
'A Typical Work Session' (earlier on Bloom 2 Bar)

Jesus Hernandez also has a good visual tutorial over on his web site.

I have also seen on this forum some good advice given by Lee Sauder on this same topic.

Blooms have a structure that Lee describes as 'like a custard' - think of a lemon meringue, turned upside down.
The centre is a hard 'nut' of iron, often quite dense, with a spongy layer, often with a lot of air spaces and more slag included around the outside. As you might guess, a larger bloom might be cut apart, so more like a wedge of pie than the whole thing like you see on a small bloom.

(There is a variation in carbon content within a single bloom as well. Lets just leave that one. If anything, this carbon variation exaggerates the effects.)

Of course, the two different densities of metal move at different rates. That's one reason a press, squeezing in one direction does work more effectively than hand tools. The raw size of the mass also works against anyone attempting this process working alone. With excellent skill and co-ordination between a master hand and striker, of course the compaction process can be carried out by hand. (Watch Lee and Mike McCarthy work some time!)

So your first step is just pressing downwards at welding heat, collapsing the air spaces of the outside 'meringue' and forcing them on to the hard nut in the centre.
This does help on the edges however, which remain ragged. I have had some luck placing the then flat disk on its edge and pressing in / down. Its a tall thin shape, with soft edges, so the press tends to slide it sideways and I certainly find that process hard to control. Also the press works in a flat plane, and most often the bloom disk is round or oval.

Taken together, I had found it just as effective to hand hammer the edges in. I would place the disk flat on the anvil, then lean way over so I can fire blows almost dead horizontal from the far side of the anvil back towards the disk and my tong hand. This also allows you to both heat and forge on section of the bloom disk at a time.

Clear as mud?

Technically, the Bloom 2 Bar Project ended (at its most generous) May 15.
I will however, continue to cross post items from my regular blog (Hammered Out Bits) here, for topics directly related to the theme of bloom into bar - and beyond.

Monday, May 14, 2012

Papers, Publishing & Research Sources

Day 72

If judged by the budget included with my OAC Project proposal, the last actual 'grant day' would have been 43 days ending April 26. I decided to extend the project work to cover two last major elements. One was the iron smelt covered in the last couple of posts here. The second was an academic paper to be delivered at the International Congress on Medieval Studies at Kalamazoo Michigan. The conference ran from May 9 - 13, with my specific paper to be presented Thursday May 10.

I've referenced the paper itself in an earlier posting here. I had given a first draft version at Forward Into the Past at Laurier University on March 31. Obviously I consider the various public presentations of both research and practical method, plus ongoing communications like this blog an esencial part of the entire Bloom to Bar project.

The revised text of my paper 'An Iron Smelt in Vinland' will be eventually be published. Session organizers Ken Mondschein and Michael Cramer are working with Freelance Academy Press to collect a number of papers from the past 'If Those Bones Could Talk' sessions into a volume. 

Not to get too (!) side tracked, what I wanted to detail here was some other excellent reference sources for those seriously interested in bloomery iron smelting.

Method :

A Practical Treatise on the Smelting and Smithing of Bloomery Iron
Lee Sauder & Skip Williams
Historical Metallurgy, vol. 36 (2). 2002
A version will be available by hunting around on Lee's Iron Smelting site
If You Don't Get any IRON...
Darrell Markewitz
EXARC. vol. 2012-1
Available on line (with subscription)

Remember there are some links to instructional methods to your top right!

References :

Iron in Archaeology - The European Bloomery Smelters
Radomir Pleiner
David Brown Books in the US is currently contacting the original publisher to see if they can acquire some copies of this volume. They are also attempting to get some of Pleiner's 'Iron in Archaeology, Early European Blacksmiths / 808612462-2'

Prehistoric & Medieval Direct Iron Smelting in Scandinavia and Europe 
Lars Christian Norbach
13 9788772887746
Available from ISD Distributing
The book costs $60 plus shipping

Iron and Steel in Ancient Times
Vagn F. Buchwald
Available from the Danish Royal Academy
The book costs 60, 56 Euros plus 21,4 Euros (to Canada).
Contact Katrine Hassenkam Zoref

Sunday, May 6, 2012

'Production Smelt' - RESULTS

 (Day 65)

I would refer you back to yesterday's post for the details of the set up for this smelt.

Furnace in use
The first thing is don't do this alone.
You *can* run a successful smelt as a lone individual. It is however a massive amount of work.
- I spent a half day clearing out an old furnace and preparing the area and laying the base.
- Then a fairly long day preparing, mixing clay and building the furnace.
(Roasting ore was done separately, but the two batches there could have been undertaken during the work sessions above).
- Another half day gathering up the roasted ore, setting the tuyere and running a slow drying fire. I broke up 3/4 of the ore at the same time.

Smelt day, I broke charcoal while the first stages of pre-heat (with wood) was taking place.
I started that day at 8 am gathering tools and getting them out and arranging the work site.
The pre-heat was extended to allow time to break that charcoal (64 kg worth / 8 bags).
The main smelt sequence itself ran over 7 1/2 hours, from first charcoal fill to start of the extraction. In the end I decided to use all of the 'Jamestown Brown' ore that I had roasted and crushed. The total ore added was just under 42 kg. The total charcoal consumed was 55 kg (7.5 full 8kg bags, before breaking). I had a real hard time getting this bloom free. I ended up having to break way 2/3 of the slag mass by chiselling it off in small pieces. I really have no clear concept of how long this took, but working down inside the hot furnace was absolutely exhausting. My guess is that I was at it at least a half hour.

The total smelting session took 13 hours!

Slag mass, the furnace just opened.
So by the time I pulled the bloom free, the bloom had cooled considerably. I did try to work over the surface with a 5 lb hand sledge. This did knock some of the clinging slag 'mother' free, but really was not effective in compacting the metal itself. I tried a fast weight measurement, but frankly I think the reading was not all that accurate. (What I recorded was 12.27 kg). Frankly, this is a much larger bloom than I normally make.

Hot bloom mass - after hand hammering
I rushed the bloom back from the rear yard into the workshop. I had started my two burner gas forge before I started the extraction, but there was no way the mass would fit. Although the bloom was closer to a red heat at this point, I quickly started the hydraulic press. I made a partial compaction, but it was obvious that the bloom was far too cold, and several larger pieces broke free. I swapped in the cutting head and made a cut from both sides, most the way through. At this point I might have been able to get the individual 'half' sections into the gas forge, but frankly, I was way past too beat to work.

Main bloom, cold and after sectioning
This morning, I was able to pull the scored bloom off the floor, and sweep with a magnet to recover any fragments.
The main bloom itself now weighs a quite respectable 8.83 kg.
I recovered another 1.46 kg of fragments. Two pieces are a good size (at 501 and 324 gms) and look solid enough that I should be able to work them down to smaller bars.
The overall yield (using the 10.3 kg total recovered) comes to roughly 24 %.

The furnace itself, despite all the pounding and prodding, was found to be in remarkably great shape the next morning. There is one very small crack right near the top edge, but otherwise the shaft is in perfect shape.
The copper tuyere might have melted just a tiny bit. I'll have to measure it to be sure. The wall around the tuyere did errode a slight amount, but it does not look more than a centimetre or two.
After a small amount of cleaning up, I'm certain it will be quickly ready for another use (Thanks Lee!)

(very) Tired but happy
(but let's get more of the gang here *next* time I decide to try this...)

This post a duplicate from Hammered Out Bits

Saturday, May 5, 2012

A Production (?) Smelt

(Day 64)

Although technically I am past the end date for the OAC Project Grant, one of the things I wanted to include was building a more production type furnace and running a test smelt.

As I had detailed in an earlier post, this furnace would include a number of features 'borrowed' from the furnaces that Lee Sauder has been using recently. (This a nice switch, as had focused primarily on clay construction earlier in my development.)
 The main features of this new furnace are:
use of a copper tuyere 
base area built of fire brick
metal sheathing over the shaft
use of sand / horse manure / clay mix

Layout with dimensionsBefore drying fire.
You can see the layout includes a very deep base area, a total of 28 cm from the centre of the tuyere tip to the hard base. When set up for a smelt, the lower 12 cm or so will be filled with charcoal fines. The furnace also has a much larger tap arch. Taken together, this should allow for possible bottom extraction of the final bloom.

The furnace is set on the upper level of the normal smelting area at Wareham. This does make it a bit tall for top extraction (top of the furnace is chest high on me). The advantage is that the bottom of the furnace is set about 18 inches off the ground, making it easier to work tapping or slag bowl modification.

Furnace interior, showing tuyere tip
This furnace will use the new forged copper tuyere (detailed here). The interior view above was taken before the drying fire was started. You can see the usual insert tuyere position, 5 cm proud of the interior wall and set to 23 degrees down angle. The flat brick seen the bottom is supporting the tap arch at this point (the clay was still damp).

Ore Roasting
Earlier in this week I had spent part of two afternoons roasting up ore. I still have a quantity of 'Jamestown Brown', a water deposited ore from that location in Virginia. A number of years back, a group of us were invited to pick some of this material that lay in a large sand bank at the rear of a rural blacksmith/gunsmith's property. Sheldon Browder & Steve Mankowski (from Colonial Williamsburg) have used this ore repeatedly since with good results.

Late yesterday afternoon and early evening I started preparing the smelting area. I started a gentle drying fire using small wood splits inside the furnace. That process continued for several hours. At the same time I sorted out the work area for today's smelt. As well I continued crushing the ore I had roasted over the last week. The ore does seem a bit 'sandy' to me, with a visible variation in iron concentration and form. At worst this may mean some extra slag tapping, but the new furnace layout should provide for this.

Its looking like I may be running this smelt today single handed. Although I have done this (once!) before, I'm expecting a hard day. Lets hope nothing goes seriously wrong with this new furnace.

Stay tuned...

This post duplicated from Hammered Out Bits

Sunday, April 29, 2012

Inspiration to Modification

Day 62

Remember these?

F- 'Split Fire Riser'
R- 'Solar Riser LH4'
Thomas Patti - 1943
(Sorry - its a horrible image)

When I saw these glass objects by Patti at the Corning Glass Museum, I immediately thought of how the hydraulic press could alter the shape of a block of steel in a similar way.

So this is what became of the concept (Very, very, first rendition)

The left corner is the result of the very first experimenting with the press day I did with David Robertson. (David had consulted heavily with me on the construction of the press before this OAC project begain.)
The tool was originally produced for potential use with my small air hammer. I never use secondary tools that much with the air hammer, primarily because of the small die surface (as repeatedly mentioned, only 1 1/2 " wide by 4 " long). Although it is true that lack of practice is part of that problem! It has a slightly tapered shaft forged from 1 1/4 ' round stock, so the working end is roughly 1 inch diameter. The shaft length is roughly 3 inches, made of mild steel. The handle is piece of flat stock, wrapped around and MIG welded on the top surface, then ground flush.

The starting block was a piece of 1/2 thick by  roughly 2 inch square.
The resulting shape was made by setting the tool on the orange hot block, then driving it downwards. I used the full power of the press (to 3000 psi), primarily to see how far through I could push the tool.
As you can see, what happened is that the tool 'bottomed out' at about 3/16 thickness. At that point the metal below the tool had most of its heat pulled off through contact with the tool and bed of the press. The increasing pressure then simply started to bend the shaft itself.

Obviously not the way to go. Interesting potential however.

The second test , at the upper right, (done April 17) started with modifying a tool. This small (cheap) ball peen hammer had been used for a different impression test initially. Result was that the pressure collapsed the walls of the eye around the original wooden handle. First I used a drift to re-open the eye and straighten the bent head. The hammer face side was forged down to approximately the same shape and size as a standard 3/4 inch taper base candle.  Last I forged down a piece of solid 5/8 " round to fit, then drove that into the eye hot to seat it.
The starting block this time was a piece of 1 inch square, about three inches long.
First the hot block was collapsed downwards into itself. With a second heat, the tool was pressed down into the block.
One unexpected result was that the ball top end actually left an impression into the mild steel top flat plate die set in the press. Not good. 

But the finished object? Closer, but still not quite.

Both tool and object prototyping continues...

Wednesday, April 25, 2012

What is a 'Working Day' ?

Day 60

The last couple of days have been a bit messed up, certainly in terms of how they might track back into the grant project.

Just how do you count a working day?
Especially if you are a self supporting artist?

People who have 9 to 5 'standard' jobs just don't get it. Yes, I do not have to go someplace at a fixed time, then do something I largely do not like, mainly for someone else's bennefit.
But I also spend more time each day (even if its broken up) occupied with my 'job'. I also typically 'work' seven days a week. I don't have any holidays.

Normally I'm up at about 7 AM (often much earlier). I dress, brush my teeth, go up to my office and turn on the computer. Grab a coffee. That puts me 'at work' by about 7:10 at the latest.
Then I'm involved in business related activity until normally 10 - 10:30.  This includes all the business communications, which I in fact do first. This may be answering questions, preparing quotes and design work. Keeping my business records (including all that tax stuff for the sole bennefit of the Government). There is time spent on 'outreach' - here being researching, writing, formatting and posting for the blogs. Attempting to keep the web sites up to date.

By about 10:30 or 11 AM, my brain is about toast. Some days the desk / computer work runs straight through to noon. By then I'm *really* fried.

During the grant project, I have been seriously trying to keep 'non grant' work to a bare minimum. I'm keeping a daily diary, when I note what I've done each day. Note that I do not consider that work required as part of keeping the Wareham Forge functional as 'non grant' time. Monday I spent a hour compiling my quarterly HST, for example.  A counter point was that this morning I spent roughly a hour and a half making up a design rough for a possible project for *after* the grant runs out. That time I will not include under the project grant.

Afternoons are generally spent in the workshop itself, normally starting some point between 1:30 - 2 pm. Once again, there is a lot more to undertake in the shop than just hammer at the forge. Supply trips (Monday morning I rushed in to purchase propane, elapsed time was 1 1/2 hours). Clean up and maintenance. Equipment construction and set up.
Now take one of the work sessions documented here, say the one shown as 'A Typical Work Session'.
First I need to figure out just what I'm going to do. This may include some organization and record keeping. Typically 15 minutes.
Then, having selected the bloom to work on, I start the gas forge and start getting the required tools, etc organized. All while waiting for the gas forge to get through its pre-heat. Typically 10 minutes.
Now I can place the bloom piece into the gas forge for its initial heat soak. Then I turn my attention to the preparing the coal forge. Clean, sieve, lay and start the fire. Wait for that fire to run through its coking phase. Normally sweep the shop floor while this is happening. Typically 30 - minutes.
By now the bloom piece is pre-heated and can be transferred to the coal forge to bring it up to welding heat. This requires some attention. I dance back and forth preparing the air hammer and hydraulic press for operation.
Elapsed time from when I entered the workshop till I pull the bloom piece out to the anvil? Typically 1 1/2 to 1 3/4 hours.
Insert forging the bloom here, normally about 1 1/2 to 2 hours.

Now at that point I'm, pretty much beat. Forging multiple kilogram masses at welding heats is exhausting and demanding work (even *with* my two machines).

Add some time shutting things down. Normally its now something between 5 - 6 pm.
I make that a 'normal' work day of 7 a to 5:30 p, with 1 1/2 hours average for lunch = 9 hours.

Then there are the *long* days.
Now do that basically 7 days a week.

I was extremely pleased - and quite surprised, to get this OAC grant! (Ok?)

Taking the amount awarded in the grant and converting it into normal working days, at 5 per week and weekends off, the total came to * 43 * working days. Use that standard, with the 14 days for the Smeltfest research trip considered additional time.  With the grant effective February 15,  the last grant day would be Thursday April 26.
See the 'day count' at the top of this post?
I have deducted all the time I have spent on things that I do not consider part of this project. I've been counting 'full days' (not working hours!)
Today's total?
* 60 * days

I'm actually going to try to squeeze out additional working time past that April 26 date for the grant project. I have an academic paper to deliver at the International Congress on Medieval Studies on May 10. My intent is to extend my own work on this project to that date.

I think the Ontario Taxpayer is certainly getting their money's worth...

PS - this piece just took me one hour to prepare

Saturday, April 21, 2012

Sometimes a great (?) notion...

(Day 58 continued)

For the last week in the forge I have been working to prepare materials with a specific object in mind.
Generally this is *not* how I have been proceeding with the project. As I do feel I still have a lot to learn about how best to approach compacting down each individual bloom. I still don't really feel confident that I can pick up a given bloom - then absolutely undertake the best possible method to produce a determined result at bar stage. There is no doubt that all this bloom to bar work is greatly increasing my skills, but...

I had three possible objects in the back of my head to create as part of this project. All three incorporate blown glass. Working with a 'raw' piece of bloom iron creates texture, an irregular outline and considerable strength.
Forged Bloom Bowl
I've always loved blown glass. It offers colour, transparency, and smooth fluid lines. The counterpoint to forged metals is obvious.

So this is the concept :
Rough for 'Fluid Core'
This most certainly is one of those times where my illustration ability falls so very short of being able to adequately picture the concept.
For 'Fluid Core', three pieces of forged bloom iron would be joined to create a tall tripod like shape. The surfaces would be roughly polished, as seen in the bloom bowl above. This creates surfaces that are both flat and shiny, but also darkly pock marked. The ragged edges from the original bloom are left in place as much a possible. Part of the technical challenge is compacting the parent bloom mass enough to be structurally solid, but not welding / folding so much as to blend in all the cracked edges.
The glass would be formed in place over the metal. On the lower surface, it would be allowed to slump down to form three lobes between the metal plates I'm envisioning the top of the glass as a long oval form.

These are the individual plates I have forged up to use for this object :
Bloom iron plates
All three pieces are forged down from the 'Slag Pit 2' bloom (# 49 - November 2011) The starting bloom mass was 4650 gm. It was the first piece that I worked under the new hydraulic press, first cutting it into four more manageable sections. (The fourth piece, smaller and more fragmented, was forged up into a working bar.)
You can see how I have drawn the individual segments into long thin plates. The next step will be shaping these into more of a triangular profile. I still have not decided if I will simply MIG weld the plates together, or make a separate cylindrical core to serve as the attachment piece.

I have already spoken to local glass artist Kathryn Thompson about co-producing this  piece (and possibly two others). I have been a huge fan of Kathryn's work since I first met her. (Kathryn was one of the contributing artists for 'Out of the Fiery Furnace' in 2005). Other than showing her my rough concept, I intend on letting her determine how best the glass work should be undertaken.

I will be using some of the OAC grand funding to directly commission this glass work from Kathryn. (Another positive effect of the grant!)

Friday, April 20, 2012

Building a PRODUCTION Iron Smelting Furnace

 Day 58

Making a bloom requires an iron smelting furnace. I have built dozens over the years, most on the 'Norse Short Shaft' model. The work on the actual smelting end (creation of the iron blooms) has been a combination of a learning process extended into experimental archaeology. Furnaces are often purpose built to test a specific variable, and commonly only used one or two times.

I have decided to take the opportunity offered by the OAC project grant to build a more durable 'production' version furnace.

The first day's work consisted of gathering the available supplies and possible pieces, plus cleaning up and preparing the site. The furnace built for last year's 'slag pit' experiments was examined to see if it could be simply repaired. 

Damage to top of Fall 2011 furnace
The nature of recording the slag pit experiments had meant picking up and moving the furnace itself after each smelt. The furnace had been returned to a prepared base and covered over with a plastic drum for the winter. The combination of all that shifting, and the winter weather, had resulted in a fair amount of damage. This certainly could have been repaired, but I decided to build a brand new furnace.

There would be a number major elements used for the production furnace which should combine to greatly increased durability :
use of a copper tuyere 
base area built of fire brick
metal sheathing over the shaft
use of sand / horse manure / clay mix
Part way through construction, with measurements
One of the things kicking around the shop was an old metal trash barrel, with the bottom pretty much rusted out. It was roughly 60 cm tall and about 35 cm diameter at the small end. Almost exactly the same size as the exterior of a short shaft furnace. I decided to use this as a combination form and protective shell for the upper shaft. The base area would be built from a circle of dense fire brick, both for durability and stability.
Firebrick base as laid out
 The furnace was constructed on the shelf that makes up one edge of the Wareham smelting area. This places the bottom base of the furnace up about 25 cm above the working floor. To create a hard bottom and stable surface, a (broken) concrete paving slab was placed first. The furnace is being constructed with a large tap arch - large enough to allow for possible bottom extraction of the bloom (although my normal method is a top extraction). The location of the tuyere will be to the left hand side as seen above. The placement of the fire bricks on edge creates a heavy and flat surface for the shaft of the furnace to rest on. The circle of standard construction bricks defines the boarder between the furnace and the natural earth surface.
Brick layer with clay fill 

The first layer of clay was a mix of 50 / 50 rough sand and standard ball clay (mixes by volume). This was used as a mortar to fill the wedge shaped gaps between individual bricks. Next the space between the firebrick circle and the outer retaining bricks was filled. Finally a sloped shoulder was created from clay to the top of the fire brick layer. A full bag of clay was required here.

Next, the bottom of the metal barrel was cut out. A slot was cut on one side, roughly 7.5 x 7.5 cm. This would be the hole allowing for the insertion of the tuyere later. The measurement from the top of this hole to the top of the barrel was 40 cm. (When positioned, the angle of the tuyere will place its tip even lower, so there should be a good 50 cm of stack height.)

Dry measures for the clay mixture
The furnace walls were composed of a mixture of course sand, shredded dry horse manure and clay. The clay used was 'New Foundry' - a higher firing temperature clay (which I had gotten from Lee Sauder). The ratio is roughly 25 / 25 / 50. This is mixed dry by hand before the water is added. (I took considerable care to make sure the mixture was fairly stiff, particularly with the first layer.) The material was kneaded up to an even consistancey, then hand wedged into balls and left to stand for about an hour before applying. (Note that Lee recommends letting the clay stand overnight to even out the moisture content. Yes - I did rush this a bit!)
First wall layer applied (tap arch at bottom right)
The individual balls were broken in half, with the individual pieces blended in carefully as the walls were built up. The metal form allowed to exert good pressure, but still keeps the overall shape consistent (and under control!) The thickness of the walls was kept to roughly 6 cm at the bottom, thinning slightly to closer to 5 cm at the top. You can see how the interior diameter is matched to the ring of fire bricks.
Because the metal barrel tapers, the interior diameter of the furnace will taper slightly as well. This is actually ideal, as it moves the tuyere tip slightly off the direct line of ore falling inside the furnace. (We have seen this arrangement reduces the amount of slag that collects on the tuyere tip.)

I finished up a long working day just as the sun was getting close to the horizon and the black flies were starting to come out. Expect some images of the final construction, once the clay has had a couple of days to stiffen up and I mount the tuyere.

Monday, April 16, 2012

Demonstrating the Aristotle Furnace

Day 54

This video clip was shot by one of the participants at my March 10 demonstration at the monthly meeting of the Ontario Artist Blacksmith's Association (OABA, through the work of editor Sean Stoughton, regularly posts video on to its own YouTube site. )
The sound quality is uneven, and as hand held footage is a bit jumpy. The beginning explaination is missing, but if you stick with the clip, you will mostly get the sense of how the small re-melting furnace works.

For more info, download a handout at:

An earlier description of this demonstration was made here on B2B : March 11 - the Aristotle Furnace

Saturday and Sunday this weekend were spent taking part in a presentation by the Dark Ages Re-Creation Company at the Royal Ontario Museum. The ongoing experimental iron smelting work was part of the presentation. Although strictly not part of the B2B project, reference to the OAC was made (via a sign).

Friday, April 13, 2012

Forging a Copper Tuyere

Day 54

This is a note of the work undertaken on Wednesday April 11 (Day 52).

Lee Sauder had this to say about his use of a copper tuyere:
1) The original inspiration to try the copper came from the Catalan furnace descriptions. I tried it the first time I tried the flue tile, after the first Early Iron at Cooperstown, so I guess that would have been late ‘04 or early ‘05. I have used them almost exclusively since, with the Coated Tyle furnaces, the Cadhinos, the big steel and refractory Aphrodite, and all the clay furnaces.
2) I have found that they will melt if they are much less than 14 inches long (this is with about 2.5 inches protruding into the furnace).
3) I looked back through my notes, I think I used the last tuyere for 45 smelts before I retired it, but I’m not sure. It didn’t fail, it was gradually thinning, and I didn’t trust it anymore.
I had made a first attempt to try out a copper tuyere for my own smelts # 7, #8, # 12 in 2005. My problem was at the time I did not have suitable copper material to work with. I had tried cutting and forming from 1/8 inch thick copper sheet. That thickness just was not enough to either withstand the furnace temperatures or transmit heat off fast enough to prevent erosion of the tip. Work with copper tuyeres was abandoned in favour of using a standardized ceramic tube (starting in 2006).

Last year at Quad State, I had picked up a large bar of copper, 2 x 1 1/2 x 12 inches. (Luckily, I paid less than current scrap prices = $20.) I had actually intended this material for an artistic forging project, but like many good intentions, the piece got tucked away and pretty much forgotten.

With the reminder caused by the slag rings recovered at Smeltfest this year, and wanting a break from the heavy forge work this week, I pulled that block out. The starting weight was 4358 gm.
The first step was to combine draw, widen and flatten the material to a rough flat bar. This was done under the air hammer - mainly 'pushing' the material under the dies. (Starting at the far end, and pushing the material back towards the tong end as the dies collapsed it.)
Copper is wonderful material forge! It is extremely soft at a dull red colour, and even when the temperature drops, it remains soft and workable. This softness also means less vibration shock back into your hands. The big problem is heating a large piece. Heating in the propane gas forge, I was never able to get it much more than a 'bright red'. The end of the material hanging out of the forge was radiating off heat almost as fast as the burners were applying it.

After the initial flattening
(sorry for poor image quality)

At the end of the first stage, I had a flat bar roughly 1/2 inch thick, 3 inches wide, and about 20 inches long. You can see most of the thickness had been transferred to length, working on the flat die on the air hammer. In the image you can see how I cut off the last 4 1/2 inches (955 gm) of material.

The remaining piece was forged to a taper, both in thickness and width, over its length. This was done in a number of steps. Initially the material was worked by placing it to 90 degrees to the long axis of the dies. Next the surface was worked under a Hoffi style crowning top die. This was followed by a fair amount of working the surface with the cross peen. Again the direction of the peening was done at 90 degrees to the long axis of the material. The net effect here (for the non blacksmiths) is to primarily force the material side to side - not end for end. Last, the surface was worked with the forging hammer to smooth out all the irregularities caused by using the peen on such soft material. At this point the edges were also hammered to create a more or less even and straight lines.

This all created a shape like a triangle with the tip cut off. To finish the work, the peen was again used, but now over a half cylinder shaped anvil tool. Also it proved just as easy to work into the hollow created by the step from horn to face on the right hand edge of the anvil. This series of more gentle strokes gradually formed the flat surface into a half curve. This was carefully rolled up to where the two edges met - creating a conical form.
This was then worked to ensure the shape was symmetrical, and straight.

Finished copper tuyere

The resulting tuyere is 45 cm long. Its finished weight is 3394 gm.

Furnace End
2.5 cm internal diameter
wall thickness 6 mm

Air Input End
5 cm total diameter (accepts standard 1 1/2 inch threaded pipe)
wall thickness 3 mm

Thursday, April 12, 2012

Credit where Credit is Due!

Day 53

Setting the Record Straight!

Part of the project grant was specifically to cover my participation in Smeltfest 2012, hosted by Lee Sauder at his Germinal Ironworks outside Lexington Virginia.
Lee, assisted by his close friend and smelting partner Skip Williams, started investing historic bloomery iron smelting methods in the 1990's. They were initially inspired by African models, then worked backwards to establish a functional and predictable technique.

Sauder & Williams, pulling a bloom from their 'African Queen' furnace.
Frontier Culture Museum, Stauton VA - 2002

I had the good fortune to meet Lee and Skip in Fall of 2002. I had only undertaken two smelts at that point, both unsuccessful. They were extremely generous with their knowledge and folding my small group (other members of DARC) into their demonstration. Although we did little more than help with some of the 'dirty jobs' I certainly learned an immense amount. They had already determined the critical high volume air flow required to correctly produce dense iron blooms. By the point I met them, they had published their research both formally and inside blacksmithing circles.

Thanks to the wonders of the internet, the Spring 2004 smelt at Wareham had a special guest, Michael McCarthy from Cooperstown NY. Mike had been smelting at the Farmer's Museum, basing his furnaces on Colonial American models. He was actually on his way back home from spending a week building and operating a Japanese tatara furnace. Although yet again tour smelt was a complete failure, a solid friendship was struck up.

Mike would organize the first Early Iron symposium at the Farmer's Museum in Fall of 2004. This gathered together Lee & Skip, Mike and myself as demonstrators, each building and operating a furnace from our various traditions. My (quite unplanned) contribution was a Norse style short shaft.

the "Gangue of Fer"
(L-R) Sauder, Williams, McCarthy, myself (back)
Early Iron 1 - Cooperstown NY, 2004

Late Winter of 2005 would mark the first of the invitational Smeltfest events hosted by Lee. Initially this was just the small group of us, concentrating on some specific aspect of furnace construction or smelting method.
Over the years a number of functional problems have been proposed and tested. These methods have then been incorporated in the continuing work of all three teams. A growing group of other enthusiasts have been included and have contributed. The core these days includes Jesus Hernandez, Shelton Browder and Steve Mankowski. Smeltfest has been fortunate to have include a number of wide flung guests on a more irregular basis, including some that have travelled a fair distance to participate. (Recent years have included Jake Keen, Tim Young and Therese Kearns from England, Jeff Pringle from California.)

In truth, the Early Iron group acts much like a think tank - with a solid practical workshop aspect. Evenings are spent in brainstorming ideas, with the raw energy of being gathered from isolation into a group of fellow enthusiasts. Days are spent testing out suggested concepts. The combination of experiences, interests and personal skills provides a unique and often intense, learning experience for us all.

My single largest contribution to the overall endeavor has been with documenting and publishing the discoveries. Almost always I am *not* the originator of these ideas. In practical work, I am typically just a 'worker bee' rather than a team leader.
I do make every attempt to make sure credit is given where credit is due.

(This clarification arose from some secondary mentions of yesterday's blog post. Tomorrow I will expand on those additional comments.)

Tuesday, April 10, 2012

Crossover - Slag Rings in Archaeology?

The impact of an OAC project grant may extend well past the intended application.

My interest in bloomery iron started with the historic process of making the iron. Although there are some scattered living traditions (notably in Africa and India), these are fragmentary at best. For Europe, the technology of making iron has changed significantly since 1000 AD, with several pronounced shifts in method, equipment and type of metal produced. In attempting to re-discover what is a 'lost' tradition, modern researchers and practitioners are guided by very limited archaeological remains alone.
The best experimental archaeology may offer insights into how to interpret what may be puzzling artifact remains.


These are some shots of slag rings recovered from two of our recent smelts (at Smeltfest 2012, Lexington VA, March 2012)

Lee Sauder has been using a heavy forged copper tuyere on all his smelts for the last several years. I'm not entirely sure just why he came up with this innovation. I believe it was in attempt to find a durable solution to the problem how the high temperatures inside the iron smelting furnaces were melting off the ceramic and steel pipe tuyeres then in use.
His tuyere was forged from a solid copper plate roughly 3/8 inch thick. First the piece was cross peened along the long axis to both spread and thin the rectangle into a triangle shape. Then the resulting form was wrapped into a cone. The finished cone is roughly 2 cm ID on the furnace end, about 4 cm ID on the bellows end. The piece is maybe about 40 cm long altogether. The closing seam is just butted together (not fused or entirely air tight).
Lee's clay 'medium shaft' production furnace.
The conical forged copper tuyere can be seen to the right

In use, what happens is that the heat the tuyere end is subjected to quickly travels back to the larger end exposed outside the furnace. The combination of radiation to the outside air, and rushing cold air down the inside surface, all combines to keep the tuyere end well before the slumping or melting point of the copper material. The result is virtually no effect to the the copper tuyere, even after many firing sequences. I think Lee has used this same tuyere for something like 30 smelts, with no damage at all!

As the rings would sit against the furnace wall

Inverted, showing the slag and ore fragments on the top surface

The slag will harden to a shell around the tip of the tuyere. These rings do not solidly attach fuse to the copper, normally hand pressure will break them clear.
You can see that both the internal and external diameters are indicated in the slag rings.
You can determine the upper and lower surfaces, with the heavier accumulation on the 'up' side of the tuyere in the furnace.
You can get some estimate of the tuyere angle. The slag has formed proud of the furnace wall, so if you assume the inner wall to be vertical, the inside surface does record the tuyere angle.

Inner surface (inverted here)
The inner diameter and thickness of tuyere can be determined.

Both the rings show cracking in roughly the same place. I think this is an effect of the cooling rate of the slag and the shape of the rings. One of the collected rings had in fact separated into two pieces ( the ring on the left in the images above).

One ring was broken into two pieces

We have worked with ceramic tube tuyeres as standard here for the last while. These are uniform, cheap and fairly durable. They also are quite obvious as a physical remain. Same goes for the iron (steel pipe) tubes we have also made use of. As the iron tuyeres are consumed with every smelt, I don't think that this material likely for VA process - just from a practical standpoint. (wasting iron to make iron?)

Copper tuyeres might be another mater. They would be 'relatively expensive' as objects, but because of their proven durability would be worth the investment for repeated smelt operations. The copper would be too valuable to discard, likely just being cut up as raw material for bronze production at the end of their smelting use. Any finds of copper cut to rings as a bronze related find? It would be the easy way to re-cycle the material.

Anyway, the slag rings are quite distinctive. Lee said he gets these every time. Worth a check against remains?? (Kevin Smith had mentioned that he had recovered some semi circular slag fragments from his excavation of an 'industrial' VA iron smelting site at Hals in Iceland. It will be interesting to see if these modern pieces in any way resemble his artifacts.)

We messed with using a copper tuyere a long while back, but at the time I did not have any heavy copper bar or sheet. The copper tuyere I made up was only 1/8 thick material, and did not transmit heat fast enough to keep the end from melting back to the furnace wall. This would have certainly produced some droplets of copper into the slag someplace. Perhaps another signature to look for in the archaeology?

(Modified from the initial posting on Hammered Out Bits)

Monday, April 9, 2012

A Week in the Forge

Day 50

The shop work this week has primarily been directly converting blooms to bars / plates.
As a fast overview of what was accomplished:

Tuesday April 3
# 15 - Smeltfest 2006 Smelt A, hematite in medium shaft furnace
Small fragment @ 559 gm
Part way through the welding process

Finished bar @360 gm
Spark test shows mid carbon content

Tuesday April 3
#49 - Slag Pit 2 - taconite in short shaft with slag pit
Continue work from March 7

Bloom pieces @ 432 and spring steel core (total 590 gm)

Welded billet ready to forge to blade

Wednesday April 4
# 30 - Smeltfest 2008, DD1 in medium shaft with blow plate
Lacy section @ 625 gm

After compression under press

Finished bar @ 393 gm

Thursday April 5
#16 - Smeltfest 2006 Smelt B, hematite in medium shaft
Main bloom @ 1770
Bloom at preheat stage

Larger plate cut to remove fractured half (@463 gm)

At the third weld stage
Finished bar @ 357 gm

Friday April 6
Completion of object started March 29 (polishing & finishing)
This object is a gift, so details to come later.

Saturday April 7
#8 - Smeltfest 2005, Lexington in Econo-Norse
Section of full bloom (included cutting) @1426 gm

After compression steps on press

forged to 1/4 inch thick plate

Other project work:

Monday April 2
Finished repairing / installing engine exhaust system for hydraulic press

Monday, Wednesday, Friday, Saturday
Blog posts.

(Of course there is the normal daily 'shop office' work of accounts, clean up, communications.)

Just in case you were wondering what I've been doing.
Half of Sunday was taken up with a customer consult on a project for later spring.

Saturday, April 7, 2012

Listening to the expert

If there is one name you will see over and over here, its Lee Sauder.

Lee, working with his smelt partner Skip Williams is most certainly the single most experienced bloomery iron worker in North America. I'd lay money he's the best counting the Europeans too. He is one of the other core driving members of the recent 'Early Iron' movement. There is no doubt that had I never met him, I would have given up on my own efforts to understand Norse iron smelting years ago.

Bearing in mind yesterdays long description of a working series with a bloom (and what went wrong) here is a link to what Lee has written as advise on the process :

Sauder's Bloom Forging Hints

If any readers wish to ease into working with bloomery iron, but are uncertain about plunging right into furnace construction (and the uncertainties of iron smelting), Lee also sells partial bloom sections and worked up bars :

Bloom Iron Sales

Home Grown, Organic, Free Range Iron Fresh from the Furnace!

Friday, April 6, 2012

A typical work session...

Day 49

Two things define a typical 'project day'.
First, there is the mornings, normally spent at my desk on the computer. This covers normal communications, business record keeping, research, - and preparing, writing and laying out blog postings (like this one).
Second, there is an afternoon session in the shop. This includes equipment set up - and actually working at the forge.

What that might look like? (1)

I have been trying to document all the ongoing work on the project. There was time spent cataloguing all the blooms, fragments and partial bars from a decade of iron smelts. There is normally also photographs and records kept on the finished bar produced on a specific work session. I've also been trying to keep the camera handy to take images of specific aspects of the ongoing work. Now and again I try to take enough images of the whole session to document the entire process of bloom to bar, set by step (2).
Now this is not exactly easy to accomplish, being both worker and photographer at the same time. Working the metal is very time dependant, specific heats being required for various processes. The camera also 'sees' deeper into the infra-red than the human eye, so records things much differently than what you might see if you were standing in the shop. Another problem is capturing a crisp image in the dim light necessary in the workshop. Flash images are crisp, but at the cost of washing out the visible colour of the hot metal.

So, this is what I did on the workshop session on Thursday April 5 ...
(click on any image for the full sized version)

Bloom - Smeltfest 2006, Smelt B
Ore - Granular Hematite
Furnace - Medium shaft, standard set up
Starting Weight - 2165 gm
Bloom Condition - somewhat granular, likely mid carbon content
Objectives - 1) Working with a larger sized bloom
2) Creation of large plate with intentionally ragged edges (for use creating a bowl form)

Error Number One I have been looking up the details of the bloom composition AFTER my working sessions.
I should have taken more care on selection of the base bloom for the specific objective (!) The higher carbon blooms are naturally more likely to fragment when working, and are not the best suited to the specific purpose in mind here.

On examining the starting bloom, it was seen there was a fragment on one end only loosely attached. This piece was worked loose and set aside for later processing. The larger piece remains was weighed to 1770 gm.

This piece would still fit into the double burner propane forge for pre-heat. The shot above is taken just after the forge itself was lit, so you can see the internal chamber itself has not come up to operation temperature.
The more important function of using the gas forge is to allow for a generous heat soak period - to ensure that the heat has penetrated through the whole mass. This continues while I am setting up the coal forge for the work session. This normally takes about 30 minutes to clean, screen, light and get through the coking cycle into a correct condition for forge work.

This is the condition of the bloom after 20 plus minutes heat soak. This propane forge will at best produce a 'bright orange to almost yellow' heat level. Although this is fine for general forge work, it is not quite hot enough to weld.
So now that the coal forge is ready, I transfer the bloom over to the (much hotter!) coal fire.

In this available light image, you get some idea of one of the first problems, which is simply fitting a bloom mass of this size into my existing coal forge - and effectively heating it. My fire box is a fairly large one, roughly 9 x 7 x 6 deep. I can easily get the *depth* of fuel for a hot fire. The problem is getting even heat around both edges of the large bloom mass. The forge is set up with a standard bottom blast, which means the primary heat direction is from the bottom as well (watch for this and its effect later).
Care is taken to increase the heat of the mass relatively slowly. The piece is constantly turned and flipped so there is the best chance of getting the whole mass to an even temperature. The intent is to get the mass up to welding temperature for the compression phase.

The first forging steps are carried out on the hydraulic forging press:

The first compression uses the larger flat plate die, also with the larger full sized bottom plate. The bloom is compressed along its natural top to bottom axis, with the flatter (top) side placed down. With quick work, it is then flipped and compressed again. At this point the 'cake' is roughly 3/4 inch thick, and still very ragged, especially on the edges.
The huge advantage of the press is that it is *squeezing* the often fragmented bloom mass together, rather than *pounding* it, as would be the case using my air hammer. This is especially important when working up the more granular higher carbon blooms. (The hematite blooms are almost like solid pieces of brown sugar in texture.)

The cake is placed back into the coal forge and brought up to welding heat again. Now the more compacted shape makes for more even heat penetration into the centre. At this point the piece is not so large that there is not fairly even heat distribution from the top and bottom of the fire.

Taking into account the action of the press, a second bottom plate is added. The cake is compressed down closer to 1/2 inch thick.

Back to the forge for another series of welding heats. This work is done with the hand hammer at the anvil. The ragged edges seen in the photo above are gently welded in towards the centre. This is done about 1/4 of the circumference at each welding heat. (A total of 5 heats were taken here)

This shot is heating prior to the last compression step. You may spot a developing problem. The size of the plate is now large enough that it effectively blocks the air blast from the bottom of the forge, not letting enough oxygen into the top layer of fuel. There is now a very marked difference in the heat being applied to the bottom surface, compared to that on the top.

The narrow 'slot' die has been placed on the press. The surface of the plate is worked over (total three compressions on the first side, four on the second). At the end of this step, the plate has been reduced to about 3/8 thick.

(there is a gap in the images here)

Next the work shifts over to the air hammer. The plate after compression is a rough oval. As the intended application is for a bowl, a more symetrical shape is desired. For that reason, the placement of the piece on the air hammer is with the long axis of the dies running the same direction as the long axis of the metal. Due to the combination of metal size and small die size, only one half of the metal can be worked at a time. So there are a number of heat / work cycles required. An attempt is made to start each cycle back up to welding heat.

Error Number Two Remember that higher carbon metals are *much* more prone to overheating.
My attention got pulled away (by something) and I ending up letting the thin plate get drastically overheated at one point. The fire itself also was starting to perform less consistently (3).

The end result here was that I ended up burning out a small chunk of the plate. As well there were some serious flaws / cracks running through one side of the surface.

Sometimes you just have to know when its time to switch gears.
With almost all the damage on one half of the plate, I used a hot cut to divide the plate into roughly two half sections. The slightly larger piece, now at roughly 6 x 3 1/2 x 1/4 inch thick (684 gm), looked solid enough to continue working down towards a possible (smaller) bowl later.

The major cracks on the other section were used like score lines to break up the piece. This piece was roughly the same dimensions, but with the bite out of one edge, the weight was 463 gm.

These were combined roughly in the relationship seen here. The two larger fragments making the two outer surfaces, the smaller plus one little piece (broken off earlier) placed into the centre.

At this point I'm into a sequence that I have used a number of other times working up smaller bloom fragments.
The pieces are stacked, and tack MIG welded on one end to a mild steel bar and to each other. There is a total of 499 gm of bloom material. (This time I remember to weigh the handle separately!)

I've had a bit of a break, considering how to continue and cooling pieces to weigh and record. I also pull the bottom of the fire apart to clean it, and set up a new coke 'cavern' for proper forge welding. This is also much more familiar territory for me - a process much like I employ for layered steel. First there is a light fast hand weld to secure the pieces. This is followed with a heavier series of hand welding to make sure the pieces are well solidified. Although it is true bloom materials can contain a lot of glassy slag, I figure adding a bit more flux (borax in my use) can't actually *hurt* anything. I take care to get the ragged edges in the stack folded and welded in. Final compaction and drawing out is done on the air hammer.

The result is a small billet, roughly 1 1/2 x 8 x 3/16 inches. You can see that there is a prominent crack along one surface.

Deciding to work with the flaw, rather than against it, I use the hot cut to divide the billet along the crack. I had hoped to just score and fold (not normally what I do btw). The pieces actually separated. Perhaps not the absolutely wisest move, I decide to use a more 'japanese' technique - just balancing the two pieces in the fire and heating from the bottom. (Hey, it works for my friend Jesus Herandez...) Maybe a bit surprisingly, I manage to get a a good heat and successful weld. Under the air hammer, I work more aggressively *against* the last weld direction (so on the edges).

The end result of *three hours* is this finished small bar. Rough size is 5/8 x 1 x 4 1/2 inches at 357 gm.

Calculating the bloom to working bar loss is a bit rough here.
From bloom to cracked plate, the numbers are 1770 to 1223 = 69% return (so 31 % loss)
From plate pieces to bar the numbers are 499 to 357 = 72 % return (so 28 % loss)
Overall bloom to bar works out to 50% yield
(but bear in mind the material lost to that overheat)
(Thanks Neil!)


1) Important Note!
Remember that the purpose of the whole project is for me to accumulate some (necessary!) experience converting blooms into working bars, and hopefully then into objects. Obviously what I've documented here is very much a *learning process* and should not be considered the 'best' way to accomplish a given task!

2) One other aspect of these images : The original higher resolution images have been transformed via Photoshop into web format detail. Generally the image size has been modified to roughly 8 x 10 inches. This, combined with the various camera positions, makes the scale of the individual images vary considerably. Some images are shot with scales, so remember to use those to determine relative sizes. For the images shot on the anvil surface, the width of the anvil is 4 1/2 inches.

3) Lee Sauder uses a side blast set up when he works blooms. The clear advantage here is the the air flow comes in from one side edge (so spreads more evenly top and bottom over a cake or plate shape. More significantly, there is a lot of slag generated in the bloom to bar process. With a bottom blast, this material oozes to the bottom of the forge, effectively blocking part of the air blast. As this debris increases, the effect is to create hot jets of super heated oxygen. Effectively these act like small cutting torches inside the forge, which with poor attention (!) can have the effect of over heating (burning!) just part of the metal contained within the forge.

PS - Crunching the images, writing and formatting this essay has taken roughly three hours. I did need a bit of a break from a 'good week' at the forge. After lunch I'll get back out there and may have something to report on later!

If anyone is counting, today would be the 29th 'standard work day' on the project. Thats counting like it was normal days with weekends off.
In actual fact, according to my project diary, today counts as the 48th full day I've worked on the project.

You're getting your money's worth...

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

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