Iron Production Experiment - Sep 2005

Date: 1 Sep, 2005

Location: Annapolis Royal, NS

Premise: All proper equipment, done in costume. The presentation at CANIRON 2005.

Experiment Notes - Norse Short Shaft Smelter

The Team:

Leader	Darrell Markewitz
Staff	Kevin Jarbeau Dave Cox Mark Pilgrim
Recorder	Neil & Karen Peterson

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:
The majority of the stage dressing was done the day before the smelt (Aug 31). The presentation included a norse tent as a background, a "sand table" forge, displays of tools, a table with displays of previous results and handouts, and the actual smelter and tools required for the planned smelt.

Mixing cob	Patching flaws	Rocks around outside	Reverse view
Location of tap arch	Tuyere location	Smelter from above	Discussion of plans

The day of the smelt dawns anything but bright and sunny... Rumour was that this was pushed in by Hurricane Katrina. The good news was that it cleared out by lunch and the day turned out lovely, although some sunburns did occur.

Sand table forge	Removing inner form	Hole for tuyere	Mark on the bellows
Darrell receiving advice	Kevin on bellows	Adding charcoal	Darrell lectures
Spreading ore	Exhausting work	Checking tap arch	Jake on bellows
Connecting air	Checking airflow	Flame from tap arch	Slag running
Scooping charcoal	Chipping bloom free	Dave removes bloom	Reducing bloom
Compacting	Crowd watching	Pulling again	Consoldation
Consolodation	Final result

There is also a movie of the extraction

The morning after
As usual we deconstructed the site the morning after the smelt taking a variety of measurements to assist in our experiments.

Tuyere	Tuyere	Tuyere	Slag adhesions
Wall colour	Wall changes	Grades of product	Bit of bloom

Time		Event	Measures
			Relative	Absolute	Total
Relative	Elapsed				Charcoal	Ore	Sand
0:00	00	addition rough charcoal, occasional gentle air blast (begins at 1120h)
0:32	32	first graded charcoal added
0:45	13	charcoal	1	4 lbs*	4 lbs
1:02	17	charcoal	2	4 lbs	8 lbs
1:22	20	charcoal	3	4 lbs	12 lbs
1:40	18	charcoal	4	4 lbs	16 lbs
1:42		seed charge	1	.75 lbs*		.75 lbs
1:58	18	charcoal	5	4 lbs	20 lbs
2:00	18	seed charge	2	.75 lbs		1.5 lbs
2:19	21	charcoal	6	4 lbs	24 lbs
2:21	21	seed charge	3	.75 lbs		2.25 lbs
2:46	27	charcoal	7	4 lbs	28 lbs
2:47	26	seed charge	4	.75 lbs		3 lbs
3:06	20	charcoal	8	4 lbs	32 lbs
3:09	22	seed charge	5	.75 lbs		3.75 lbs
3:32	26	charcoal	8	4 lbs	36 lbs
3:32	23	seed charge	6	.75 lbs		4.5 lbs
3:49		sand	1	1 scoop			1 scoop
3:58	9	sand	2	1 scoop			2 scoops
3:58	26	charcoal	9	4 lbs	40 lbs
3:59	27	seed charge	7	.75 lbs		5.25 lbs
4:16	18	charcoal	10	4 lbs	44 lbs
4:17	19	sand	3	1 scoop			3 scoops
4:17	18	seed charge	8	.75 lbs		6 lbs
4:40	24	charcoal	11	4 lbs	48 lbs
4:43	26	sand	4	1 scoop			4 scoops
4:43	26	seed charge	9	.75 lbs		6.75 lbs
5:07	27	charcoal	12	4 lbs	52 lbs
5:07	24	sand	5	1 scoop			5 scoops
5:08	25	seed charge	10	.75 lbs		7.5 lbs
5:51	44	charcoal	13	4 lbs	56 lbs
5:55	48	sand	6	1 scoop			6 scoops
5:56	48	seed charge	11	.75 lbs		8.25 lbs
6:42		Changed to Electric Blower
6:46	55	charcoal	14	4 lbs	60 lbs
6:46	51	sand	7	1 scoop			7 scoops
6:47	51	seed charge	12	.75 lbs		9 lbs
6:54	8	charcoal	15	4 lbs	64 lbs
6:55	8	seed charge	13	.75 lbs		9.75 lbs
6:56	10	sand	8	1 scoop			8 scoops
7:03	9	charcoal	16	4 lbs	68 lbs
7:11	8	charcoal	17	4 lbs	72 lbs
	16	ore charge	14	1.5 lbs		11.25 lbs
7:20	9	charcoal	18	4 lbs	76 lbs
		ore charge	15	2.25 lbs		13.5 lbs
	19	sand	9	1 scoop			9 scoops
7:30	10	charcoal	19	4 lbs	80 lbs
		ore charge	16	3 lbs		16.5 lbs
		sand	10	1 scoop			10 scoops
7:42	12	charcoal	20	4 lbs	84 lbs
		ore charge	17	3 lbs		19.5 lbs
7:52	10	charcoal	21	4 lbs	88 lbs
		ore charge	18	3 lbs		22.5 lbs
8:01	9	charcoal	22	4 lbs	92 lbs
		ore charge	19	.75 lb		23.25 lbs
8:03		reduce air flow
8:10	9	charcoal	23	4 lbs	96 lbs
8:22	27	reduction charge	20	.75 lbs		24 lbs
8:22	12	charcoal	24		100 lbs
8:35	13	charcoal	25		104 lbs
8:42		reduce air flow
8:45		reduce air flow further
8:47		air flow reduced to minimal - remaining charcoal removed
8:52		consolidate bloom with wooden thumper
9:02		remove bloom and consolidate
9:06		return bloom to smelter
9:11		remove bloom and consolidate
		return bloom to smelter
		remove bloom and consolidate
		return bloom to smelter
		remove bloom and consolidate
		return bloom to smelter
		remove bloom and consolidate

NOTES:
Charge times recorded at END of unit addition

*  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
All sand charges are based on a 'standard scoop' - weight of ??? lbs
  Estimated from known marks

YIELD:  5 lbs (estimated)

Our presentation at CANIRON was a partial success.

As a smelting history demonstration, it was excellent - and very well received. The fact that equipment problems and substitutions put us into early evening for the bloom extraction made the showering sparks extremely impressive.

Dr Brigitta Wallace was an observer for most of the day long smelt - plus for the forging contest the next day. As with other archaeologists who have seen us at work, she felt she had a much better understanding now of how the physical remains relate to actual process.

What happened:

Slag
We used the pure taconite ore, which has almost no silica in it
We researched and used a commercial high temperature clay for the smelter walls, no melting means no silica.
No silica and no silica means NO SLAG. No slag means no carbon control.
We thus (predictably) produced a block of CAST iron.
Although an attempt to create more slag via addition of beach sand - this was done on the spur of the moment and without real science. With some thought we should have been able to run the numbers on this.

By the way - the finished bloom mass was stolen late the night of the smelt. We have one tennis ball sized fragment. With image evidence we should be able to guess the total weight from the fragment - but really do not have any yield measurements.

Air
The large bellows continues to create problems. Modifications to the bag and plate construction, new handle shape, new frame - all made these physically easier to use.
There remains a problem with air delivery. Right now there is no downstream valve set up.  We think what happened is that as soon as slag / sintered ore started to obstruct the tuyere, we actually were pushing air from one chamber into the other as much as pushing air to the smelter. Simple flap valves should help with this. With use of a mechanical air system - the reaction kick started almost immediately.

Lesson Learned: we should make sure we have a mechanical system on hand regardless. A hand cranked blower at least.

Kevin points out (via his reading of Pliener):
Historic iron production sites often show three or four types of smelter construction - one each. Then there will be dozens (or hundreds) of one of these styles. Likely explanation is that they tried a couple of different set ups to utilize local materials. Once something worked - they duplicated that over and over. Ore / clay / smelter shape /  charcoal /air system all fit together to produce a 'best possible' combination. Our major problem is that we keep changing multiple variables almost every time. If you look at the smelts with good results - you see they are times when only one (or two) variables are changed.

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.