Minden Ore Goo - Loki Smelt

Marcus was able to run a sample of the Minden 'Iron Goo' ore through his testing. This gives us the values bellow, along with his comments.

As a background here, the source material was gathered at a roadside ditch just south of Minden Ontario in the spring of 2006. David Robertson and I had discovered the deposit quite by accident on a trip up to the area. A rock cut along the road contained a layer that was an iron ore deposit. Some of the rock was gathered, but it proved to be only a small amount of iron oxide layered in with a course sand and compressed into a sandstone like material. When this material was roasted, it became only slightly magnetic - which I took to mean only a small amount of iron was actually present.
I was hopefull that the presence of even some iron in the rocks might lead to a bog ore deposit close by. The contour of the land is such that the drainage from the rock cut runs down about 100 meters to a low bog. On a second trip to the site, I did examine the bog itself, but although some of the surface signs for bog ore existed, I did not find a deposit of primary bog ore.
What I did find was a particular material throughout the drainage ditch along the base of the rock cut. This was a redish brown colour, and about the consistancy of chocolate pudding, that layed in a loose layer just at the bottom of the water in the ditch. It could be gathered by straining it out through your fingers. Over roughly two and half hours I pulled out enough of this material to fill about five standard 5 gallon plastic pails. As you might guess this incuded a lot of water.
Over the next several months, I allowed the pails to dry in the sun, eventually rendering down the material to a dry clay like consistancy yielding 22 pounds (10 KG) total.

Showing the ore source

This is 'just barely' enough ore material to undertake a smelt. Most definately the relative iron content becomes very important in determining this. The DARC smelt series points to a threshhold amount or ore required - which also relates to the smelter size. Given our own use of a relatively standard size at roughly 25 cm diameter (10 inches), we have consistantly found that we need at least 8 - 10 kg of ore to get the correct formation of a slag bowl and what I'm going to call a 'seed bloom'. This using the Virigina Rock Ore sourced by Lee and Skip, which is in the 60 % iron oxide range. Ore addtions OVER that amount just appear to increase the overall size and density of the bloom being created. (Note that this is at best a rough rule of thumb - I'd be happy to hear from those experimenters who have gotten different and better results!)

For those of you who attended Early Iron 3 this year, the demonstration smelt I carried out on Saturday used the Minden Iron Goo as the ore material. The 'Loki' smelter was somewhat reduced in diameter - to roughly 20 cm / 8 inches. Detailed notes on the conduct of the smelt can be found at:
www.warehamforge.ca/ironsmelting/Early Iron 03/LOKI-EI3.html
And also on the BLOG at the posts:
Friday, October 20, 2006
'Loki' Smelter - part 2
Thursday, October 19, 2006
'Loki' Smelter at Early Iron

SO - to the POINT

Skip had commented at the time when the smelter was pulled apart that he wondered about a possible high silica content to the starting ore material. He remarked how the slag was much more glassy than what is normally seen - almost like a poor quality soda glass. This observation is borne out by the content of the ore sample - with about 18% silicon dioxide present. The relative iron content of the ore is also certainly on the low end - at only 42 %.
If you extract the volatile elements (as Marcus comments on) the starting ore is closer to 60 % iron oxide. Note that the ore was NOT roasted before it was added, which of course we would normally do. In this case this initial step was not undertaken because of the powdery quality of the material. Although roasting would have increased the relative purity of the ore, it also means that the total effective amount of iron ore added to the smelt was closer to 6.3 KG / 14 lbs total. This is again under what we are finding as our minimum threshold.

The Loki smelt did produce some metallic iron. There was only a small amount, about .68 kg / 1.5 lbs. This was mainly in the form of some small fingers of high carbon cast iron, plus a number of small oval shaped balls of similar material spread through the glass slag. If the effective ore amount is considered to be that 6.3 kg / 14 lbs however, this means a return of ore to iron at about 9 %.

One obvious concern is the smaller particle size for this ore material. I think this is primarily responsible for the high carbon content of the metal produced. Higher additions of ore to charcoal might correct for this. Without a doubt, considerably more of this specific ore needs to be used if any useful result is expected.

Yet ANOTHER series of experiments to add to the list!

Darrell

****************************
Tuesday November 28

Hi Darrell,

On Friday, I got back the data for the sample of the Minden goo that you
gave me. I have reproduced it below. Looking at the data, the high loss
on ignition value (LOI) shows that there are a lot of volatile
components there. This is most likely structurally bound water, but may
include some carbon dioxide from decomposition of carbonates. I did not
request total carbon analysis, so have do not have the information with
which to comment on this. If all these volatiles can be removed by
roasting prior to smelting, then the ore could produce an initial
material that is ~61 wt% Fe2O3. If not, then a lot of the weight that
goes into the smelter will not be iron and will be driven off at an
early stage of smeltin (taking heat to do it). Although the volatile
content of the ore is similar to that which you gave me from LAM, it is
much more silica rich, so has an overall lower Fe content (42 vs. 66 wt%
Fe2O3). Full analyses of the LAM material are on the web site. If you
have any questions about these data, let me know.

Regards,

Marcus.

*Sample ID* 06-0356-0001
Client ID Det Limit MIN01 Volatile-free
units wt% wt% wt%
SiO2 0.01 17.88 25.67
*TiO2* 0.01 0.13 0.19
*Al2O3* 0.01 3.11 4.46
*Fe2O3T* 0.01 42.4 60.87
*MnO* 0.01 0.42 0.60
*MgO* 0.01 0.61 0.88
*CaO* 0.01 3.55 5.10
*Na2O* 0.01 0.78 1.12
*K2O* 0.01 0.71 1.02
*P2O5* 0.01 0.07 0.10
*LOI* 0.05 29.61
*TOTAL* 99.26

Fe2O3T = total Fe expressed as Fe2O3

Lectures in Peterborough This Week

If anyone is in the Peterborough area over the next couple of days...

I will be giving two evening lectures this week;

TUESDAY - November 21
Peterborough Public Library
7:30 PM - Lower Level
for the Peterborough Historical Society

'Vikings West to Vinland'

One thousand years ago the first Europeans sailed west from Iceland, to Greenland and eventually on to the territory they called Vinland. Who were these people, and how were they able make such a voyage? What did the Norse see there that made them pick this spot for their outpost? Today we can travel east to that same spot, the tip of Newfoundland's Northern Peninsula at L'Anse aux Meadows. What will we see there today that proves that this is the site of 'Leif's Houses'? Explore an archaeological puzzle through images and examine replica objects with Viking Age specialist Darrell Markewitz.

WEDNESDAY - November 22
Catherine Par Trail College - Trent University
about 7:00 PM - Room 102
for the Society for Creative Anachronism

"Iron in the Middle Ages'

How was iron manufactured from raw ore in the Middle Ages. How did the blacksmith then transform it to useful objects. Just what was the typical smith making? Our examination of artifacts and replicas will centre on just what kind of objects are most useful in re-creating daily life of the Medieval period. A special focus will be the most recent experimental iron smelts by the Dark Ages Re-creation Company.

I believe both lectures are open in interested members of the general public. Hope to see you there...

Gilling West Sword Replica # 2

This is a longer post than normal - in that it is a photo essay of the ongoing work on this project. In an earlier post (Tuesday, July 18, 2006 - 'Replica of the Gilling West Sword') I had talked about the process of taking this early Viking Age artifact sword and preparing to forge a modern day replica.

After the plates that make up the individual billets that are used to form the core rods are prepared, the next step is to weld the blocks and draw them out to rough length. As a reminder, each of the stacks are made up of 9 layers of wrought iron / mild steel / L6 alloy, and are roughly 6" long by 1" wide and about 1 1/4" tall. Each is bound together with three loops of 'soft iron' fencing wire.

This first image shows the starting stack, the billet after welding and the rough drawn out core rod. For knives, I normally start with a stack roughly 4 inches long. My main coal forge has a good sized rectangular fire box, but even still, the six inch length of these stacks was about the longest that can be easily brought to an even welding heat.

For successful forge welding, the key is managing the fire. You can see here I have laid two lines of fire brick alongside the fire pot to further increase the size of the heat zone. The total height of the fire is roughly 12 inches, with at least four inches of burning fuel below the work being heated here. Use of a classic 'cavern' style fire is also essential to both evenly heating the metal and achieving the correct oxygen free atmosphere around it.

As soon as the stack has come up to a dull red heat, I generously flux all edges of the metal with borax. I personally use 'Twenty Mule Team' washing soda. This material still contains water in its matrix, so tends to bubble up a lot when first applied. This certainly DOES lead to more of a mess around the forge and quicker accumulation of heavy slag / clinker in the bottom of the fire pot. However, the washing borax is quite cheap (about $2 per pound) and easily available at the local grocery store. (For a longer discussion of Welding and Fluxes, see Wednesday, August 23, 2006 - 'Norse Meat Spit - Period Fluxes?'.)

This is certainly a dramatic image, if not the best illustration. Once the stack is fluxed, it is carefully brought up to an even welding heat. The stack is constantly rotated, as the lower surface in the fire is hotter than the upper. It is critical to a successful weld that the heat evenly penetrates the entire stack. A balance must be made between producing high temperatures in the forge, but at the same time not interjecting excess oxygen into the atmosphere surrounding the metal. Once the ideal temperature is reached (judged by colour and experience), the stack is quickly moved to the anvil and a series of rapid hammer strokes are worked down the surface on both sides. The pattern of these strokes not only 'tack welds' the loose plates, they also serve to sweep out the flux. This in tern floats out any debris or oxide that may have formed in between the individual plates. After 10 to 15 minutes of careful heating - the actual weld itself takes about 30 seconds! I like to do my first weld using a hand hammer, usually a 1000 gm / 2.2 pound for a combination of control and penetration.
(Sorry that I do not have an image of the actual welding. I was taking these photos myself while I worked, so they represent places in the ongoing process where I could stop for a couple of seconds to grab the camera.)

Just after the weld, while the block is still yellow hot, those binding wires should be removed. Remember these have been holding that loose stack of plates together during the initial heat to welding temperature. There is a bit of a trick to this - getting the thick stack to temperature WITHOUT burning off the much thinner wires. An alternative to using wires would be to MIG weld the plates together at the end. I'm more of a traditionalist - and the wire method is how I learned (and teach for that matter). Reguardless, the wires are now loosely welded into the flat side of the block. These are removed by grabbing the loose sides with a pair of pliers and then with a rolling motion pulling each set free. You could weld the wires into the block of course, but the way they project from the sides would make this difficult and messy. Removing the wires should be done as quickly as possible to preserve the heat in the block and reduce exposure to room oxygen (limiting scale formation).

Once the wires are removed, the block has the edges quickly wire brushed to remove old flux and any fire scale. If the hammer stokes of the first weld have been controlled and even, the sides should have remained relatively straight. The sides all round are fluxed again and the block returned to the fire. The block is once again returned to an even welding heat throughout. Careful observation during this heating will point out any areas were the initial weld may be imperfect. This will show in colour breaks through the material. Ideally there will be none of this, but if its obvious an area of the block is not welded, a second hand hammered weld may be required.
Now, I used to do my second consolidation weld using a heavier (1.5 kg / 3.5 lb) hand hammer. And then go on, again by hand, to flatten and draw out the welded billet. This process of a single weld and draw, undertaken alone, would take me roughly 2 1/2 hours. I could manage this heavy work three times over the course of two days - and then would have to take a half day off to rest. A couple of years back I invested in the first prototype of David Robertson's small air hammers. This tool, with the required air compressor, was not cheap. It does have the great advantage of not only speeding the time of drawing out, but more importantly to me (especially these days!) using MACHINE rather than MUSCLE power.
The second consolidation weld is thus taken under the air hammer. The force of the hammer ensures that the entire height of the stack is correctly welded. Starting at a welding heat also means a considerable amount of the drawing out also can occur in the same step. I work over the entire bar quickly to ensure the welds, then concentrate on drawing out using the residual orange heat.

This shows the relative size of that first weld to draw sequence. The upper stack is ready for the fire, the lower billet has been tack welded, consolidation welded with first draw. the width of both of these remains at roughly 1". You can clearly see how the thickness has been converted to length. The dark bands that show on the welded billet are the iron layers. The central bar is a core rod drawn to rough length for comparison.
I have been welding the prepared stacks two at a time. The process is to weld and run the first draw, then weld the second stack. Once both billets look pretty much as you see above, I will then finish up drawing the two to rough length. I never make it practice to attempt more than TWO billets welded as described in a single fire - or as a single work session. Both the fire and myself are too tired to perform correctly on a third weld series!

Here you can see the process of drawing the roughly 1/2 thick by 10 inch long billet out to a rough core rod. At this point I am taking each of the potential cores out to roughly 3/8 square by 24". Once all the stacks are welded, I will determine the actual length and dimension required and prepare them for the twisting process that is the hallmark of a pattern welded blade.

More to come...

Westward Viking - Dr Birgitta Wallace

"The Historic Sites Association of Newfoundland and Labrador is very pleased to announce the recent publication of Westward Vikings The Saga of L'Anse aux Meadows, by Birgitta Linderoth Wallace. The book was edited by Shannon Lewis Simpson, and the design was by Vis a Vis Graphics. This publication is 128 pages long, with an extensive bibliography, and full colour throughout. It is designed to give the general public and visitors to L'Anse aux Meadows a background on the site and its position in the Norse/Viking settlement of the North Atlantic in an accessible manner. The book contains many photographs and pictures, and has a soft cover."

The official launch date for Dr Wallace's latest book is November 23 (at St John's NFLD). At present she is working on another book on the same topic, but this a more academic treatment. She is also working on the "Where Is Vinland?" segment of the GREAT UNSOLVED MYSTERIES IN CANADIAN HISTORY web site.

For more information on Westward Vikings, including ordering information, go to my unofficial web site:

see : www.warehamforge.ca/Westward Vikings


Birgitta is an old friend and mentor. She is a close advisor for the Norse Encampment living history program at L'Anse aux Meadows.

Darrell

'Redemption' Smelt - 11/07/06

Over the weekend, members of DARC gathered here in Wareham for a general workshop session. I had marked the date initially as an iron smelt. General forge work was done on Saturday, and Sunday was the day for that smelt. This turned out to be one of those times that things did not go well. We ended up with a block of slag and hardly any metal at all.

For a report on the Sunday smelt (the raw experimental data) you could go to :
www.warehamforge.ca/ironsmelting/1106data.html

I was pretty frustrated because the smelt on Sunday had not turned out. There were a couple of small lumps of iron - maybe a pound between the three. So Monday late morning I packed all the required gear out to the smelt area and ran another smelt.

This time I positioned the base using charcoal fines at the correct level - as we had learned and have been doing normally. (I feel THIS was the reason the Sunday smelt failed.) On Sunday we had used a 'natural' base of wood ash from the preheating plus settled charcoal - which proved way too porous. The slag as it forms obviously just runs through the charcoal and settles too low into the furnace - and too far away from the heat generated at the tuyere.

The height of the smelter was extended another 30 cm by the use of a sheet metal cylinder. The clay came to 60 cm above the tuyere. This extra height made a considerable improvement on the efficiency of the smelter. The charcoal used was from a local small producer. It is all oak, and comes pre sized to very even 1" pieces. This fuel is also extremely dry - so the weight per standard pail is a bit less (at 3 lb 12 oz). Neil has suggested that we start to measure volume as well as weight (basically density).

Showing the top of the smelter with a fresh charge of ore.

This is the THIRD firing of the clay cobb furnace, and the smelter itself seems to have stabilized.. There is a single crack on the front face that could use repairing, but other than the expected breakage around the tap arch, the smelter suffers hardly any damage at all. The ceramic tuyere also is almost totally intact. This was the second use of it, and it appears ready for yet another firing. As Skip had suggested, the clay sinters and then gets coated inside with a layer of slag at a stable shape. These two factors certainly appear to be protecting the smelter at a stable configuration - again as he suggested. For this firing I did nothing other than work three bricks in to form a larger tap arch.

For the Monday smelt, I gathered up all the slag from Sunday and re-cycled it through the smelter. Intentionally, I used a volume of this 'gangue' as the initial charge - to allow this material to establish the new slag bowl bottom. This seems to have worked well. I then charge the ore I had on hand. There was roughly 20 lbs of pre-roasted Virginia Rock Ore, which did have to be crushed. Once this had been added, I used the balance of the gangue material from Sunday, to a total of about 20 lbs.

Working on Mike's latest brain storm, I started charging in fairly large amounts - and kept it at that level. I was using considerably more air than we have used in the past. The 'theoretical' amount for this 25 cm diameter would be between 600 to 900 litres per minute, but the air rate was set to roughly 1050. I had a solid consumption of roughly 4 lbs charcoal every 8 minutes (see the notes). I charged ore at 3 lbs per pail and the gangue at 2.25 lbs. I kept the gangue a bit lower than the ore as the pieces were larger and figured (correctly) that they would take longer to heat.

Showing the first 'self tapping' of the smelter

What Skip calls 'Happy Slag' self tapped latter into the sequence - about when it should. The slag was dense, black and fluid - all the signs of a good iron rich slag. This was also re-cycled. I had absolutely no problem with blockage of the tuyere through the smelt.

For extraction, I burned down the charcoal to just above tuyere level and then clear remaining charcoal and thump from the top. The size of the bloom suggested it would be pretty hard to extract from the top. So I pulled the bricks and dug out the base of fines. By then thumping from the top - the bloom pretty much popped out the bottom. Even working alone, the extraction was very easy. I might suggest that at least for a slightly smaller bloom - clearing the base and then thumping the slag bowl down certainly appears to make extraction a LOT easier.

Showing the cleaned bloom with partial cutting

The biggest challenge was trying to compact the hot bloom working alone!
I got a classic bowl shape to the bloom, about 6 inches across and maybe 3 inches thick. It proved easy enough to knock off the attached slag and mother to clear the iron. I did work it over with a hand hammer to at least get rid of the really loose stuff. I started to cut - using my bloom axe in my left and a roughly 5 lb sledge with one hand (not very well!) I got maybe a third of the way down before the bloom was just to darn cold. Again thanks to Mike for the idea of using the green wood stump. I could never have held the bloom to an anvil working alone.

The finish weight is roughly 15 lbs. Note that this was off my fishing scale so only an approximation. I'll take it into town today and see if I can use the Post Office scale. This appears a very nice, classic bloom shape. Feels pretty dense. I will spark test it latter today and get back to you on the actual weight and guesstimated carbon content.
For a report on this Monday smelt (the raw experimental data) you could go to :
www.warehamforge.ca/ironsmelting/1106B-data.html

Darrell

Early Iron 3 - Smelt Two to Norse Anvil!

I may have mentioned that I undertook two smelts at Early Iron 3 in Peter's Valley. The second smelt was with the assistance of Dick Sargent, and was fired on the wrap up day on Monday Oct 9. In past years this day sees the departure of most all the participants early in the day, with only the four of us team leaders hanging over till the Tuesday. Also this has come to be 'weird smelt day' - usually some wild idea contributed by Mike McCarthy.

Mike's weird idea this time was 'stick it too it'. Instead of our standard slow ramping up of ore from a single scoop / pound per charcoal charge (4 lbs in this case), we STARTED ore charges at close equal amounts of ore to charcoal. This amount was increased from that level to about as large an amount as the smelter could stand. The maximum ore additions reached 6 lbs per bucket, with 4.5 lbs each 9 minutes being the averages.

Rather than try to insert another table on to the BLOG - I will just send you off to the Wareham Forge / Iron Smelting area. If you want to see the field data for this smlt - go HERE
(www.warehamforge.ca/ironsmelting/Early Iron 3/EarlyIron3-B.html)


The smelter was a re-use of the standard Flue Tyle teaching / experimental test bed developed by Lee Sauder & Skip Williams. They had set this up for a Saturday demonstration smelt, which was undertaken by Mike assisted by Lee. The furnace was in pretty good shape, just needing a bit of patching with clay around the tap arch and the tuyere. For the Monday smelt I used one of my normal ceramic tube tuyeres, but one of Lee's high volume blowers. (Sorry - I don't have air volume numbers for these - but it would be the range of 1000 litres per minute.)

The overall numbers were a bit surprising. Roughly 100 lbs of the Virginia Rock ore were charged (about 45 KG). Because of the high ore additions, considerably less charcoal than normal was consumed, roughly 130 lbs total (58 kg). The smelt was also faster considering its volumes - about 4 1/2 hours altogether (plus an hour for pre-heat).

The end result of this smelt was a very nice solid bloom. Extraction was basically from the bottom. Unfortunately there was no large sized scale on hand to get a finished weight. The bloom was slightly consolidated, then sectioned in half, and one half into quarters.

Lee and Mike had been working in the forge most of the day on a sculptural piece created from the bloom they had made on Saturday. Normally I'm pretty beat after a day long smelt, but they were keen to compress my quarter section to see what the quality was. Under Lee as forge master, with most of the striking labour supplied by Mike, and some contribution of myself as second striker, the section was forged to a very faithful replica of a Viking Age anvil.



The finished object is rough cube 3 inches (7.5 cm) on a side. Finished weight is almost exactly 2 kg (roughly 4 1/2 lbs). It tapers slightly to the base (to permit solid mounting in a wooden stub latter). One of the sides shows fracturing, but it was decided to leave this crack as is rather than weld it shut. This was done to accent the nature and origin of the source material. At this point the surface is just hammer flattened. I have not decided if I will actually further smooth or polish the face. As it is the anvil will certainly serve its function. Right now the remaining three faces have two differing rough radius curves and one section that is relatively sharp. Again these edges could be dressed to even them up, but they will certainly prove functional. Lee's estimate of the relative carbon content (based on his extensive experience forging out blooms) is that this iron is some place between a 'pure' wrought iron and a modern mild steel in carbon (say equivalent to a 1010 material).

We all were extremely happy with the result. Although there are no measurements of the starting weight of the bloom before forging, the comparison of the ore weight to finished object is of note. Although not an exact ratio, the finished production yield is roughly 18% - considerably better than has been suggested by some other researchers

Darrell