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Iron Smelt Vinderheima May 2009

Date: 30 May, 2009

Location: Vinderheima

See also: Darrell Markewitz's ironsmelting site

Premise:

  1. 1000 years ago the norse visitors at L'anse aux meadows attempted a smelt. We plan to reproduce that smelt.
  2. This marked the first of four smelts in a sequence designed to test several variables currently outstanding in our knowledge of the smelt.
  3. The smelting area was laid out as suggested by the archaeology of L'Anse aux Meadows, more photos of the furnace hut, and a discussion of the vinland furnace.
  4. Blower to allow us to measure required airflow for this new structure.
  5. Use a medium walled clay (not cobb) furnace structure.

Experiment Notes - LAM Clay Smelter

Diameter:  20 cm Stack above Tuyure:  50 cm Tuyure Diameter:  2 cm I.D.
Tuyure Distance above floor:  15 cm Tuyure Angle:  23° Wall Thickness  5 cm

The Team:

Leader Darrell Markewitz
Staff Ken Cook / Darrell Markewitz
Recorder Darrell Markewitz
Ore & Charcoal prep Ken Cook / Richard S.
Ore prep Robert Gissing / Neil Peterson / Ken Cook
Archaeological records Neil Peterson
Strikers Neil Peterson / Richard S.
Construction Darrell Markewitz

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.
Smelt Totals
Total Charcoal ?? Kg Weight of Bloom 4.89 Kg Total Elapsed Time: 4:30
Total Ore 16.6 Kg dry weight [18 kg 'damp' wieght as added] (LAM analog) Yield: 33% Bloom Quality low carbon to tool steel - see Darrell's Youtube video for a discussion

Discussion:

This smelt went shockingly well. When you change the ore, smelter size, and smelter construction you don't expect good results. Not the first time. Yet we had a nearly picture perfect smelt with a few very understandable issues.

For an in depth discussion of the input and output figures please see Darrell's blog of June 5th. There is also a nine minute overview video of the smelt availavle on youtube

Conclusions:

Overall set up
The physical arrangement of the site was tight but workable.
Smelter size
Generally we run smelters with a 30cm inside diameter as suggested by the archaeology of scandinavia. In this case the archaeology at LAM suggests a 20cm inside diameter. This required us to reduce the airflow and adjust the burn times to ensure the ore stayed in the reducing stack for the required time.
Ore Analog
This was a second version of the analog developed by Robert. This one is designed to match the bog ore local to L'anse aux meadows with a iron weight of 64%.
Ore weight
The archaeology at L'anse aux meadows suggested 15 Kg of slag [10Kg actually recovered] and a 3kg bloom from 18Kg of ore. We used 18Kg of (damp) analog and generated a 4.89 Kg bloom with 8.6 Kg of slag recovered.

The test was undertaken on a clean bed of sand, which allowed recording of the debris field created by the smelt, related to the known positions of the workers. This will be able to be directly compared with the records of the L'Anse aux Meadows excavations.

Layout of the smelter area Finished Construction After the drying fire. Drilling the tuyure hole at the required angle
Liam helping Ore Analog Cracks developing Temperature readings
Self Tapping Burn down Locating the bloom Beginning consolodation
Consolodating Consolodation Reconstructed After removal
Final Bloom



CLOCK ELAPSED EVENT AIR     CHARCOAL     ORE    
            UNIT COUNT TOTAL UNIT COUNT TOTAL
      gage LpM P bucket   kg scoop   varies
12:00   start wood splints pre-heat                  
12:50   very gentle air (maintain burning)                  
14:10   gentle air 26                
14:40   Adjust Air 70   2.5            
    ash level about 5cm below tuyere                  
14:52 2:52 start main sequence                  
                       
12:00   fill with graded charcoal       2 2        
12:13 :13 charcoal       1 3        
12:30 :17 charcoal       1 4        
12:35   air increase (by sound) 80 675.6 3            
12:46 :16 Charcoal       1 5        
12:48   temperatures: 1=1170, 2=1375                  
13:04 :18 charcoal       1 6        
13:11   First ore as slug             1 1 1
13:21 :17 charcoal       1 7        
13:35 :14 ore added as 1/2 kg       1 8   1 2 2
13:47 :12 ore added as 1/3 Kg       1 9   1 3 3
13:53   Temperatures: 1=620, 2=985, 4=1245, 5=1250, 6=1140, 7=1105, 8=1040, top=625                  
14:05 :18 high slag level, ore as 1/2 Kg       1 10   1.5 4.5 4.5
14:18 :13         1 11   1.5 6 6
14:35 :17         1 12   2 8 8
14:51 :16         1 13   2 10 10
15:07 :16         1 14   2 12 12
15:31 :24 Temperatures: 1=720, 2=960, 4=1100, 5=1100, 6=1115, 7=1000, 8=870, top=800       1 15   3 15 15
15:42 :18         1 16   3 18 18
15:54 :12 start burn down       1 17        
    TOTALS                  
    Time 4:30 hrs              
    Ore 18 (16.6 dry weight) kg   Analog          
    Charcoal ?? kg              
    Bloom 4.89 kg              
    Yield 33 %              
    Slag ~8.6 kg              
    Total output recovered 13.5 kg              

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: 10 July, 2009
Text © Darrell Markewitz, 2008   Photographs © Darrell Markewitz   Copyright details
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