Friday, May 31, 2013

4th RE-ARC Conference

My smelting partner Neil Peterson and I travelled the (long!) distance down to Re-Arc 3 last fall. It was absolutely worth the time and trouble. We greatly enjoyed ourselves (see the earlier review).

This is the session I have offered for this year's conference:

'Forging the Viking Age'

   Scandinavian culture was known for the quality of its metalwork,
   especially in iron. Just how did the tools available effect the
   creation of the object? Is there an effect from the qualities of the
   metals available themselves? Join artist blacksmith and Viking Age
   specialist Darrell Markewitz for this combination demonstration and
   hands on workshop session. A reconstructed 'sand table' charcoal
   forge, along with replicas of Norse blacksmithing tools, will be
   used. Those wishing to participate need to be dressed in natural
   fibre, long pants and work boots (jeans and T shirt ideal).

Monday, May 27, 2013

Course Iron Smelt - RESULTS

I ran a course here at Wareham over the weekend 'Introduction to Iron Smelting'
(see :  http://www.warehamfo...urse/index.html )

The two students were Jeff Evarts and Greg Eamon

The fellows built a very good clay cobb furnace and prepared most the materials on Saturday. The design was a pretty standard 'Short Shaft', about 70 cm tall and 28 cm internal diameter. The material was an even mix (by volume) of chopped straw, beach sand and dry potter's clay. The tuyere was a ceramic tube (kiln support), set at 22 down and inserted by 4 cm, 12 cm above a charcoal fines base.
Air provided by one of the industrial blowers the Early Iron group all uses, gated to roughly 800 lpm.

Charcoal was broken and graded maple and oak ( added separately), total of about 50 kg.
Ore was a mix of 'Barton's Run' limonite, DARC Dirt Analog and some rock ore from Quebec I had been given by Antoine Marcal. Total used was 30.4 kg.
The main smelt sequence ran over about 4 hours (plus burn down and extraction, maybe 7 hours total with the preheat). Our burn times were extremely consistent, averaging 9 - 10 minutes per standard charcoal charge. Ore additions started at 1 kg, peaked at 2 kg per charge.

The final bloom was extracted from the bottom of the furnace (rather than my more typical top extraction). With only two of us available for the smelt (Jeff took ill), labour was a bit short, so it was off to the hydraulic press!
This might have resulted in a bit more slag being forced into the surface of the bloom iron than would be normal. Later forging will tell on that.

The result of weighing after some rough compaction and cutting : total 10.4 kg. This represents a roughly 35 % yield - certainly great results.
The bloom does appear a bit crumbly, but the slightly lower temperature of the initial compaction (after running back from the furnace to workshop) may be part of the reason. There was no spark test made at this point.

Excellent work by our two latest members of the iron bloomery community!

    Resulting bloom, partially compacted and sectioned
  • crushing.jpg
    Furnace in foreground, Greg smashing ore in the back

Friday, May 24, 2013

Pushing (Hot!) Air...

 " My main question is what is the optimal air pressure and/or Volume. I realize too much air and you could have cast iron and erode the inside of the smelter, and not enough air, no Iron. "

Sauder & Williams have described their experience in a number of articles : 'A Practical Treatise on Bloomery Iron Smelting'
There are a couple of versions Lee wrote, ranging from a shortened verson for the Anvil's Ring, to a formal academic paper. Check Lee's web site (

They found - and my own work and that of the stronger voices here certainly supports - the use of higher volumes of air. The short value is to use 1.2 - 1.5 litre of air per minute for every square centimetre of furnace interior cross section at tuyere level.
Most of us are using furnaces in the 25 - 30 cm diameter range. That 'magic number' works out to something around 800 lpm. I have a table up on my web site : http://www.warehamfo.../flowrates.html

I have done some in line pressure readings. Forgive the ruggedness of the instruments (pretty much cobbled together!)
The measurements I have taken show air pressures in the range of 3 - 5 psi with my own successful smelts. This may be more a curiosity than a useful indicator.
Does anyone else even measure that? How?
Think of the difference in hand feel between a blacksmith's blower and something like a vacumm cleaner - or a hand powered bellows...

Remember that its always better to have TOO MUCH air - rather than not enough!
You can (and we all do) reduce the operating temperature of the working furnace by adding increasing ore quantities in with your charcoal additions.

In terms of easy practical measures, again most of us are using a standard 'bucket' for our additions of charcoal. Most of us in North America are using a standard 'galvanized pail', which holds roughly 2 kg of charcoal.  Timing how long it takes to add this consistent measure gives a very useful measure of 'burn rate'.
Again for furnaces in the size range indicated, we have found the ideal burn rate is roughly 8 - 10 minutes per bucket / 2 kg.
Europeans usually will record 'kg per hour'. Using the Sauder & Williams method, that would mean roughly 15 - 12 kg per hour.
(You will see that typical European methods use only half to a third that amount. The results are predictably smaller yields and much lacier blooms!)

Of course, the specifics of your furnace design, type of ore, even charcoal type, can all alter this advice. There is a quite complex interplay between a very large numbers of individual elements for a truly successful smelt. Those with experience will certainly agree there is 'More Art than Science' at work here!

(Preparing to teach this weekend's 'Introduction to Iron Smelting' course at Wareham...)
    Industrial blower with in line pressure and wind speed (volume) gages

Thursday, May 23, 2013

About the Air...

Seth wrote to Don Fogg's Bladesmith Forum:

I have seen tuyeres adding to or helping to reduce wall erosion. What causes this and what am I looking for in a tuyere to help prevent it?

Right to start, we all need to remember that the exact working of any individual iron smelting furnace is a complex interplay between a very large number of variables! Your individual application of possible raw materials (ore, furnace, even charcoal) may certainly modify this basic level description. (!!)

Mike McCarthy proposed a working model for what is happening inside an iron smelting furnace during a late night discussion at Early Iron 1, back in 2004. I think his concept still stands up in the light of continued observations and experience:
McCarthy's original diagram - 2005
'The air blast inside the furnace makes a torus centered on the tuyere.'
My original notes on the discussion - 2005
This torus (bagel shape) is off centre, with the lower lobe smaller than the upper. (This due initially due to the effects of heat.) As the slag bowl develops, the shape is further distorted, with more of the air being deflected to the upper side of the tuyere.
Air Flow in a Working Furnace
The available air blast will effect the absolute size of the reactive area (reduction zone) inside the furnace.
Effect of VOLUME
VOLUME is important, because the reduction process of iron oxide both requires a certain volume of CO gas, but also a certain amount of effective time to take place. Things like the density of your ore, and its particle size, are contributing factors.
With low volume air, the core of the furnace may well be hot enough. But the individual ore particles may not have enough time at temperature and reaction chemistry to reduce. They may well fall to the bottom of the furnace without ever hitting an effective reduction zone.
Effect of PRESSURE
The PRESSURE at which the air is introduced into the furnace from the tuyere will determine the penetration of the air into the mass of charcoal within the furnace. At low pressure, the air remains close to the tuyere tip, which is also likely to put your highest temperatures closest to the furnace wall around the tuyere.
This is why using a rotary blacksmith's blower is often not found to be very effective for an iron smelting furnace. You may have large volumes - but with almost no pressure, the air simply does not penetrate the furnace.
Most hand powered bellows systems will certainly produce adequate pressures. Many European experimenters will use stones placed on the top plates of their bellows to control with fair consistency their air delivery pressures.

We have found that the ANGLE of the tuyere is critical to an effective iron smelting furnace.
Effect of ANGLE
If you place your tuyere too 'flat" (horizontal), what happens is that the air will not penetrate into the bottom of the furnace, leaving the effective heat 'ball' sitting too high. This in turn lets the developing slag bowl also form too high up in the furnace. The result is that you end up with a shallow slag bowl, with little room for a bloom to accumulate. As well, the liquid slag will also be sitting too high up around the tuyere, and quickly will 'drown' the air blast.

If you place your tuyere too steep, you move the air blast so it will be pointed directly at the developing bloom. Since you have oxygen at high temperature, it effectively acts like a cutting torch, and slicing your bloom apart as fast as it accumulates.
Effect of Angle on Bloom Formation
At Lee Sauder's Smeltfest research session in 2005 (if my notes are correct!) we specifically investigated the effect of tuyere angle. Through this series, we found the "best" angle for the tuyere to be 22% down from horizontal (plus or minus 5).

The next variable on the tuyere is how far the tip is inserted proud of the interior furnace wall by 5 cm / 2 inches. This helps to move the effect of the upper lobe of the torus of air away from the furnace wall.

Just to mess that element up, the material that your tuyere is made of will most certainly effect its durability over the life of the smelt:
Although using a piece of simple mild steel pipe will work - you are certain to find it will burn away quickly, moving the hot air to flow back against the furnace wall and start to erode it. 
Ceramic tubes are considerably more durable to furnace temperatures. Although these will burn back as well, our experience is that these endure long enough to prevent excessive wall erosion.
Experience has proved the most durable tuyere material is heavy forged copper. Lee Sauder has used the same copper tuyere for dozens of smelts will virtually no damage.

Putting the whole package together, you get something that looks like this:
Overall Diagram of Working Furnace
Of course you can elect to control the heat effects and wall erosion by modifying the design of the furnace itself.

Making the furnace body a flask shape, instead of a simple cylinder is one possibility. The ideal appears to be increasing the diameter at tuyere level to by the same amount that the tip of the stands clear of the furnace wall. (In effect a total of plus 10 cm beyond the diameter at the top.)

A second possibility (developed by Michael Nissen) is to insert a relatively thin plate into the heavier furnace wall - around the tuyere point. In practice, the highest temperature on the wall, thus the most erosion effect, occurs over a rough oval, 10 cm below and to the sides of the tuyere, and extending about 15 cm above it. The 'bellows plate' system relies on the atmospheric cooling off a thin cross section, in the range of 1 cm / 1/2 inch from a plate installed in that area.

Of course I do have to warn everyone that the working systems described above are most certainly not the only way to produce iron in a bloomery furnace!
A lot of combined experience has shown these elements do combine to make a very effective small scale bloomery however.

Sunday, May 19, 2013

'Layers' at Elora

As I had mentioned in a previous post, I had been selected as one of ten artists to contribute to the 2013 Elora Scupture Project.

'Layers' 2010
I had created a smaller 'sample' version of the concept for the 2010 Styl 2 (Style Squared) exhibit. All the pieces in this series need to be wall hung and no more than 12 x 12 inches square. I had envisioned the piece actually being a major public art sculpture. In the range of 3 feet tall and 10 feet long. (The original smaller piece is now available as part of my submissions to the 2013 Styl 2 exhibit.)

I was of course (!) extremely pleased when a full sized version of 'Layers' was chosen for the summer long public exhibit of the Elora Sculpture Project.

'Layers' 2013
Artist's Description :

' Under our feet, often hidden, lay the layers of individual days, compressed by time into stone. Trapped within the layers lie elusive impression of past lives. Rushing waters sometimes expose these layers, allowing us to glimpse and attempt to interpret these often fragmented records - before weather and water erases them forever... '

'Layers' was originally inspired by images of weathered granite from eastern Georgian Bay, the ground down and exposed stubs of ancient mountains. The sculpture takes the form of a large panel, set tilted back on one edge. The panel is composed of a series of individual metal bars. Each is composed of differing metals, from antique wrought iron to modern stainless steel. All are hot forged in various ways, with additional surface textures and treatments added as well. These bars are left untreated, and intended to weather naturally as exposed to the elements, the differing metals and surfaces aging with differing rates and effects.
 In its full sized rendition, 'Layers' is roughly 4 x 4 feet. It has a mounting frame that holds it up off the ground about 18 inches, tilting the surface back slightly.

The work is 'on loan' for the duration of the Elora exhibit, all sculptures on public view until the Fall this year. It is for sale (with the understanding it would be delivered after the Elora showing).  Considering my original intention for a long narrow form, 'Layers' is composed of two individual panels. The edges are set, and the back mounting designed, so that the two could easily be mounted in either the current square, or the long narrow formats.

Detail - Upper section
Detail - lower section
The individual sections that make up each panel range in width, from 1 to as wide as four inches, with most at 2 inches wide. A wider range of physical forming techniques have been used in the full sculpture than is seen on the smaller original sample. A good number are textured flat bars, using various shaped forming tools under the air hammer. Several are braids of smaller diameter metal stock, which was then flattened. Polished stainless steel, solid stainless bars, applied bronze, galvanized sheet have all been used to create variations in surface colours as the sculpture naturally ages on exposure to the elements. The colour effects seen here on the 'fresh from the forge' surfaces are intended to shift with time.

Detail - text element (click to read)
 I wanted to include some indication of human history in the concept of ancient layers. After some consideration, I decided to use a version of my favourite stanza from the Viking Age Havamal (Sayings of the High One) :
Kinsmen die
Cattle die
You will die
One thing never dies
The reputation of the dead
I had considered using Nordic runes (even Old Norse!), but in the end decided to use simple rune like letters in standard English. This so the viewer could read the inscription. *

I was further pleased by the placement I had been given. There is a small green space right at the core intersection in the older section of Elora. (NW corner of Mill and Metcalfe). Five of the ten submitted sculptures are circled around this open and landscaped space. 'Layers' is placed close by the side walk that runs along the east side, in the upper corner of the space.

Placement - as seen from the pathway inside the park space.

* There is a bit of personal ego at work here. Given the durability of the materials and the nature of the work,  'Layers' most certainly will endure longer than I will. (!) The 'dead man's reputation' here might easily be my own...

Saturday, May 18, 2013

Iron Smelt at ICMS - first overview

On Saturday May 12, I mounted an iron smelting demonstration at the 48th International Congress for Medieval Studies, at Western Michigan University, Kalamazoo MI.

The two day presentation was sponsored by AVISTA - The Association Villard de Honnecourt for the Interdisciplinary Study of Medieval Technology, Science and Art

The images bellow are scooped from the MiLive / Kalamazoo Gazette web site :

All images by Matt Gade

You can view an article by reporter Theresa Ghiloni, along with the sideshow of full sized images by following this link.

There was also some video shot of the extraction by fellow researcher Dr. Mike Cramer

My assistant and smelting partner Neil Peterson does figure dominate in the video and images above! Excellent work was done by conference members Keeney Swearer and Lisa Anne Conner for both the build and smelt days. 'David' helped on the build, 'George' was the second striker seen.

I would like to thank Steve Walton of AVISTA for organizing the demonstration.

For those curious:
Ore type : DD Analog, enriched with hammer scale
Ore total : 25 kg
Bloom weight : 5.4 kg

More images and detailed report in the works

Tuesday, May 07, 2013

Elora Sculpture Project

I am pleased to have my larger sculptural piece 'Layers' as part of this year's Elora Sculpture Project:

 There is a public opening / reception on:

Saturday May 12
2 pm

I will not be able to attend. I will be mounting a demonstration iron smelt at the 48th International Congress for Medieval Studies in Kalamazoo MI. (yesterdays posting).

On the downtown Elora map, you will also see Styll Gallery marked in red.
I currently have two earlier pieces on display at the gallery:

First is two of the panels of the larger arbour 'Paris Metro' installed against the south wall containing the lower sculpture garden.

Second is the extended version of 'Celts at the Gates - Shield and Spears' which is mounted at the top of the stairs leading from the store's rear deck to the stairway.  (This piece was included in 'Ironwork Today'.

This would also be an excellent chance to take a look at the Styll 2 exhibit!

Sunday, May 05, 2013

Iron Smelt DEMO - at ICMS

I will be undertaking a full bloomery iron smelt demonstration at:

the 48th International Congress on Medieval Studies 
Western Michigan University 
Kalamazoo MI 
May 10 & 11, 2013 

Session 523 
Swan Pond 
Friday - roughly 9 am - 4 pm : Furnace build and materials prep 
Saturday - roughly 9 am - 5 pm : Full iron smelt 
Extraction planned for 4:30 pm 

Sponsored by : 
The Association Villard de Honnecourt for the Interdisciplinary Study of Medieval Technology, Science and Art 
Michigan Technological University 

Although this is one of the official sessions of the Conference, it will also be taking place in an area open to the general public as well (outdoors!) Along with my assistant Neil Peterson, I will be expecting to answer questions over the course of both days. 

Preparing to Extract a Bloom

 The planned for furnace will be our standard Norse Short Shaft, built of clay mixture and set on a block plinth. The ore to be used is a variation on our 'DARC Dirt' bog ore analog (here enriched with roughly 25 % hammer scale). With roughly 39 kg ore analog available, the expected yield is for an 8 - 10 kg bloom. Air will be supplied by an electric blower.

General Furnace Build
Anyone interested in bloomery iron smelting is invited to come out and watch!

Map to the Demo Site - see Campus Map
I will also be making a formal presentation at one of the regular sessions:

Session 64
Thursday May 9, 1:30 pm
Fetzer 1045

   I'll Huff and I'll Puff - Observations on Air Delivery in Bloomery Iron Furnaces

Given a good quality ore and a suitable furnace, the most critical factor in determining the size and quality of the iron bloom produced in a direct process iron smelting furnace is the air delivery. A decade of experiments with Early Medieval type furnaces has shown that to create blooms most like the archaeological samples, high volumes of air are required. How does this reflect back to the design of the bellows equipment itself? If specialized equipment is required, are their further cultural implications?

Full Conference registration required for that session.

I would like to thank Steve Walton of AVISTA for organizing this demonstration.

Thursday, May 02, 2013

Styl 2 (Style Squared) 2013

Styll Squared Exhibit
Styll Squared 2013
Beginning mid April, Styll is once again exhibiting a collection of 12' x 12" wall art pieces. The collection is made up of craft in all mediums and represents artisans that are not normally shown at Styll. These are one of a kind works so stop by frequently to see the new works being added to the mix.

Directions / Hours
Once again I will be offering pieces for the excellent 'Style Squared' exhibit. (In the image above, one of my pieces 'Toxic' can be seen second row from bottom, third in from left).

I submitted two pieces I had created in past years specifically for this year's exhibit :

'Toxic' - 2011
'Layers' - 2010
 Right now I am rushing to complete a full sized (48 x 48 inches) sculptural panel for which 'Layers' was a small test. The larger sculpture was selected as one of the submissions for the Elora Sculpture Project - 2013. The installation will be on Saturday! (more to come on that).

I am allowed to enter a total of four individual pieces into the exhibit.
My plan is for two more pieces, hopefully to undertake later into May:
- 'The Webs We Weave' that will use a patterned back plate with a web formed of bronze wires standing up above the surface as a shallow 3 - D layout.
- 'Bloom of Bloom' (? Not so sure on that title) that will have a shallow bowl shape attached to a mirror polished stainless steel background via a rare earth magnet. This will allow the bowl of bloom iron to be removed if desired.
(more to come on those as well)

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

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