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Iron Production Experiment - June 2005

Date: 11 June, 2005

Location: Vinderheima

Premise: All proper equipment, done in costume. A test run for the presentation at CANIRON 2005.

Experiment Notes - Norse Short Shaft Smelter

The Team:

Leader Darrell Markewitz
Staff Kevin Jarbeau / Dave Cox
Recorder Neil &Karen Peterson
Charcoal Monkey Ken Cook
Animal Wrangler Vandy Simpson

Smelt_cd Reports of all of our iron smelting efforts along with more articles and information are available on the "Iron Smelting in the Viking Age" CD from the Wareham Forge.  Copies of the CD can be purchased here.

Setting up the smelter:
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Overview Locking the bellows For our friends at Royal Oak One more for Royal Oak
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150 lbs of charcoal Jiffy-pop Smelter Corn!

Time Event Measures
Relative Absolute Total
Relative Elapsed Charcoal Ore
0:00 00 addition rough charcoal, gentle air blast        
0:33 33 first measured charcoal 1 4 lbs* 4 lbs  
0:44 11 charcoal 2   8 lbs  
0:59 15 charcoal 3   12 lbs  
1:09   seed charge 1 .75 lbs*   .75 lbs
1:16 17 charcoal 4   16 lbs  
1:26 16 seed charge 2 .75 lbs   1.5 lbs
1:34 12 charcoal 5   20 lbs  
1:42 16 seed charge 3 .75 lbs   2.25 lbs
1:50 16 charcoal 6   24 lbs  
1:59 17 seed charge 4 .75 lbs   3 lbs
2:08 18 charcoal 7   28 lbs  
2:24 25 seed charge 5 .75 lbs   3.75 lbs
2:27 19 charcoal 8   32 lbs  
2:33   switch to electric blower - rate at D (815 L/M)        
2:37 10 charcoal 9   36 lbs  
2:47 10 charcoal 10   40 lbs  
23 full charge 6 1.5 lbs   5.25 lbs
2:56 9 charcoal 11   44 lbs  
full charge 7 1.5 lbs   6.75 lbs
  air rate at B+ (625 L/M )        
3:08 12 charcoal 12   48 lbs  
half charge 8 .75 lbs   7.5 lbs
3:19 9 charcoal 13   52 lbs  
full charge 9 1.5 lbs   9 lbs
3:24   slag tap        
3:31 12 charcoal 14   56 lbs  
full charge 10 2.25 lbs   11.25 lbs
3:41 10 charcoal 15   60 lbs  
full charge 11 2.25 lb   13.5
3:50 26 slag tap        
3:53 12 charcoal 16   64 lbs  
full charge 12 2.25 lbs   15.75 lbs
4:04 11 charcoal 17   68 lbs  
full charge 13 1.5 lbs   17.25 lbs
4:16 12 charcoal 18   72 lbs  
full charge 14 3 lbs   20.25 lbs
4:33 17 charcoal 19   76 lbs  
full charge 15 3 lbs   23.25 lbs
4:46 13 charcoal 20   80 lbs  
half charge 16 .75 lbs   24 lbs
4:59 13 charcoal 21   84 lbs  
  begin burn down phase        
5:17   air flow reduced to minimal - remaining charcoal removed        
5:28   bloom removed        

Charge times recorded at END of unit addtition

*  All charcoal charges are based on a 'standard pail' - weight of 4 lbs 
All ore charges are based on a 'standard scoop' - weight of 3/4 lbs
  Estimated from known marks

YIELD:  7 lbs (estimated)
About 30% return on ore weight

 Some photos of the norse boys working the bellows.  Notice the two different ways to use the pit.

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Ketill in pit Ketill standing tall Slag Running

As the temperature was in the "very high" range we aborted the use of the bellows part way in.

consolidating the bloom

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Shove out charcoal Thumping Removing the bloom First strike
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Flattened Bloom More consolodation Hand finishing A little more
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Bloom cooling Measurements

We also used this smelt as an opportunity to test presentation techniques

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Tent Forge Table Finished iron Info table
Talking to public

It was too damn hot!

As a seasonal activity, our feeling is that iron smelting would be undertaken (with good reason) in late fall if not early winter. Slaves are indicated for the labour.

The new bellows was finished up at about 5 pm Friday. Then work was started on the smelter - untill it got too dark to see. This was finished up the next morning. With adding all the set up for the presentation, we were about ready to start the pre-heat at just after 10 am - not too much after schedule. By that time it was already pushing 30 degrees!

The split wood preheat ran for about an hour. Started in with full charcoal and bellows work at about 11:30 (although the "clock" as usual was reset to 1200h). We were measuring shifts on the bellows using the water jar, on a 6 minute rotation. After about two hours, we started to realize that we were going to kill ourselves. Kevin was by far the best on the bellows action, Dave had the muscle to manage, and Darrell was just managing to hang in there. A command decision was made, and we switched to the electric blower at 2 1/2 hours into the smelt. As we were getting ready, we let a number of our DARC support team try a shift on the bellows - I don't think any of them wanted a second shift on it.

We did leave the belows out for the public to try. None of them would work it even a good part of a 6 minute shift by the water jar!

We did set the blower rate to roughly the same volume (by sound) as the bellows was producing. This gave us and end result that would have been approximately the same.

The initial consolidation, done just as the bloom was extracted, proceeded extremely well, Some fragmentation from the primary mass ocurred, but a good sized block was forming up. A second consolidation was done, using the smelter with extra charcoal added as a giant forge. Dave and Ken on the sledge hammers were quite effective. On the third heat, everyones attention slipped. The bloom ended up moving right up against the air blast - and we effectively overheated and burned the metal. In our estimation, we not only ruined the surface, but also lost about 1/3 of our mass. Very bad.

The end product is a block of metal about 6 long by 3 wide by 2 thick with ragged edges. Total wieght at this point is about 2 3/4 lbs.

What we learned

The biggest thing was we learned to judge the activity of the smelter by sound alone.

The smelter itself is effective in design - but requires a shallow pit below it to provide the required insulation at the base. The construction should allow for at least a second use with some internal patching. It cannot be moved after the first use however. (A new smelter will have to be built for CANIRON)

The bellows should provide enough air to complete the reaction effectively. The bellows action requires too much effort to operate (especially in plus 30 temps!). A number of modifications have been suggested, including rigid internal hoops and altering the top plate shape. There is some question about enlarging the tuyere diameter, this requires some more research.

As was estimated, there is a bottom end to the physical reaction, in terms of a minimum amount of ore required before any bloom can form. We likely were pretty close to this bottom limit at 20 lbs ore. The size of bloom we produced compares with archaeological samples.

It was generally agreed that if we had extracted the small bloom, then added a bucket of charcoal and used the smelter as a forge for two or three consolidation heats, the mass of the smelter would have remained hot enough to then proceed with a second smelt. Historically, this would allow for a couple of smaller and more easily managed blooms to have been produced in series, rather than one large bloom (more typical of modern experiments).

Discussion was made of holding a smelt in late October (schedule permitting). The experiment objective would be to test out this last idea, running a 'two bloom' smelt over a period of roughly 8 hours.
[In fact we ran a single bloom smelt in the same smelter in early Novermeber -- see here for details]
Smelt_cd Reports of all of our iron smelting efforts along with more articles and information are available on the "Iron Smelting in the Viking Age" CD from the Wareham Forge.  Copies of the CD can be purchased here.
      Updated: 4 Dec, 2007
Text © Neil Peterson, Darrell Markewitz, 2007
Photographs © Individual artists
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