sml logo Dark Ages Re-Creation Company sml logo
Overview
Oct 12, 2015
Jun 20, 2015
Apr 25, 2015
May 11, 2013
May 27, 2012
Nov 5, 2011
Oct 9, 2011
July 28, 2011
June 11, 2011
Nov 6, 2010
Aug 21, 2010
June 12, 2010
Nov 7, 2009
Oct 11, 2009
May 30, 2009
Nov 8, 2008
Oct 12, 2008
Jun 14, 2008
Apr 13, 2008
Oct 27, 2007
Oct 8, 2007
Jun 10, 2007 - Excav.
Jun 9, 2007 - Second
Jun 9, 2007 - First
Nov 5, 2006
Sep 1-2, 2006
Jun 10, 2006
Jun 10, 2006 - Tools
Nov 4, 2005
Sep 1, 2005 - CanIron V
Jun 11, 2005
May 14, 2005 - OABA
Jan 14, 2005 - Consolid.
Oct 24, 2004
Jun 3, 2004
Jun 3, 2004 - Design
Jun 3, 2004 - Questions
May, 2003 - Analysis
May 2003
May 2002

Iron Smelt Vinderheima Nov 2008

Date: 8 Nov, 2008

Location: Vinderheima

See also: http://www.warehamforge.ca/ironsmelting/

Premise:

  1. Experience with Icelandic setup & bellows plate/blow hole
  2. Overall set up is a totally earth surrounded smelter at the end of a slot - with the layout similar to those at Hals
  3. No bellows frame in position this time
  4. Use a medium walled clay cobb furnace structure.
  5. Use a bellows plate construction
  6. Use blow tube arrangement for the tuyere (which can quickly be modified to our normal insert tuyere if required.
  7. The aim is for a 3 - 5 kg bloom. (Hals size in range of 15 x 15 x 10 cm)

Experiment Notes - Norse Short Shaft Smelter in a frame

Diameter:  26 cm Stack above Tuyure:  42 cm Tuyure Diameter:  2 cm I.D. (blow hole 5cm)
Tuyure Distance above floor:  20 cm Tuyure Angle:  25° Tuyure distance from blow hole  2.5 cm

The Team:

Leader Ken Cook
Staff Neil Peterson / Darrell Markewitz
Recorder Darrell Markewitz
Ore & Charcoal prep Ron Ross / Anatoli / Yasmin
Archaeological records Ron Ross / Anatoli / Yasmin
Strikers Neil Peterson / Ken Cook
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 48 Kg Weight of Bloom 4.25 Kg Total Elapsed Time: 5:00
Total Ore 23 Kg (Virginia Rock ore / Hematite grit) Yield: 18% Bloom Quality mild steel

Discussion:

The bloom was less consolidated on extration than what is seen from a smelter with an insert tuyere - more of a 'lumpy' texture. It also was positioned a bit futher back from the air inlet than expected, and had a marked crescent shape. As with the Thanksgiving smelt (which also used the plate / hole) there was a choke point at roughly 2 1/2 hours into the ore charging / about 7 kg. The developing slag bowl threatened to drown the air intake. On this attempt we were better able to control this, and the smelter would settle down once the slag evolved from the early green silica type to the later black iron rich type.

Conclusions:

Overall set up
As with the thanksgiving smelt there were no particular problems with this working arrangement.
Use a bellows plate construction & Use blow tube arrangement for the tuyere
It was clear that the team needs more experience working with this type of furnace set up. In itself, the bellows plate was found to work extremely well. The thinner material did in fact withstand the higher temperatures surrounding the air blast quite effectively. Leakage around the plate was due to clay shrinkage, as the body of the smelter had been baked dry before the plate was installed. Fitting the plate while the body of the smelter is still damp is expected to greatly reduce (if not totally eliminate) this effect.

The blow hole arrangement proved to be more of a problem. It was clear that the system was working correctly for the first portion of the smelt sequence. Consumption rates were slightly reduced from those seen with the insert tuyere, but still within what was considered the effective range. (A rate of between 6 - 12 minutes per 2 kg charcoal is sought, for this experiment the rate averaged 13 minutes per charge.)

Problems were encountered as the slag bowl began to reach the level of the air hole, Attempts to clear the hole were compounded by the restricted access because of the bellows frame combined with the lack of experience on the part of the operators with this type of air system. Modification of the air tube and adapting the air hole to correctly fit should be made (in line with suggestions by Michael Nissen)

The production aim for this experiment was for a 3 - 5 kg bloom, similar to those suggested for Hals (size in range of 15 x 15 x 10 cm). Despite the early problems with the blocked air hole, the team produced a 4.25 kg bloom.

Taking measurements Rodding out Blockage building up Inside view
Overlapping tappings Slag tapping Removing charcoal Preparing the thumper
Thumper in action Main bloom mass Second bloom piece Front wall
     
Anatoli sketching      



CLOCK ELAPSED EVENT AIR     CHARCOAL     ORE    
            UNIT COUNT TOTAL UNIT COUNT TOTAL
      gage LpM P bucket   kg scoop   varies
                2      
12:00   start wood splints pre-heat                  
14:20 2:20 gentle air 4                
14:38 2:38 fill with rough charcoal       3 3 6      
                       
0:00   main sequence start 9   4            
0:16 16 start graded fuel 61 500              
0:20 4         1 4 8      
0:31 0:11         1 5 10      
0:44 0:13         1 6 12      
0:54 0:10         1 7 14      
0:56   first ore added - Virginia Rock                  
1:06 0:12         1 8 16 4 4 0.8
1:16 0:10         1 9 18 4 8 1.6
1:26 0:10         1 10 20 4 12 2.4
1:37 0:11         1 11 22 4 16 3.2
1:49 0:12         1 12 24 4 20 4
2:03 0:14         1 13 26 4 24 4.8
2:20 0:17 hematite / rock blend (.8 + .2)       1 14 28 4 28 5.8
2:38 0:18         1 15 30 4 32 6.8
2:44   air problems / pull tap block                  
2:49   air to full   1000              
2:50 0:12         1 16 32 4 36 7.8
3:02 0:12         1 17 34 8 44 9.8
3:15 0:13         1 18 36 8 52 11.8
3:29 0:14         1 19 38 8 60 13.8
3:38 0:09         1 20 40 8 68 15.8
3:50 0:12         1 21 42 8 76 17.8
4:00 0:10         1 22 44 8 84 19.8
4:11 0:11         1 23 46 8 92 21.8
4:19 0:08 start burn down       1 24 48 8 100 23.8
                       
4:51 0:32 burn down completed                  
5:00 0:09 extraction                  
                       
    TOTALS                  
                       
    Time 5 hrs              
    Ore 23.8 kg   Rock 8.4 kg Hematite 15.4 kg
    Charcoal 48 kg              
                       
    Bloom 3.25 kg              
    Yield 14 %              
                       
    Slag 16.6 kg              
    Gromps 0.1 kg              
    Total output recovered 20 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: 7 Dec, 2008
Text © Darrell Markewitz, 2008   Photographs © Darrell Markewitz   Copyright details
Contact us