Monday, April 07, 2008

Iron Smelting Seminar in Thy 2008 - Schedule

The following was written by Jens Jørgen Olesen of the Heltborg Museum. He has given me kind permission to publish it here.
As you would have seen in earlier postings on the Seminar, this is an invitational event limited to just 30 participants.
Location: The Heltborg Museum / near Skjern, Denmark
Dates: Tuesday 29 April - Sunday 4 May

Jens also provided this information:
Saturday afternoon is a public day, where visitors and sponsors are invited to come and hear about what we are doing. We hope everyone will take part in this! ...
The Museum is open every day during the seminar. The visitors are allowed to watch the experiments...

The Heltborg Museum starts its regular seasonal opening on May 1.

The museum web site (hit the side bar for Heltborg Museum for a slide show) :



The experiments

The purpose of the Iron Smelting Seminar in Thy is to create a link between recent and older archaeological finds of iron smelting sites and the knowledge of people who work with the practical side of iron smelting. The seminar will provide opportunities for them to test their ideas in cooperation with archaeologists and metallurgists, and maybe in this way help to solve a few of the riddles that still exist within the field of prehistoric iron smelting.

The four main types of furnace known from Scandinavia are the earliest slagrum furnaces of the Espevej/Skovmarken type, followed by the slag-pit furnaces of Drengsted or Trøndelag type, to the slagtapping furnace of the Viking Age, best known from Norway and Sweden. Last comes the Evenstad type which appears in different versions, but which is known from written sources to have been run with wood as fuel.

The Tranamo group from Sweden will base their experiments on the Viking Age furnace where they have great experience. They bring their own ore which they have been working with and which was presumably used in the original furnaces.

Peter Hjort Jensen from our own iron smelting group will experiment with a medieval furnace, the Kjellerup furnace, a danish variant of the Evenstad furnace. We do have some experience with this furnace, but the results are not impressive so far.

Arne Jouttijärvi will construct an Espevej furnace on the basis of new finds from the Herning region. These form the subject for Martin W. Olesens coming Ph. d. dissertation.
Michael Nissen will work with a similar furnace. Within the latest year he has conducted several experiments with this type at the Ribe Viking Center.

Arne Espelund will conduct experiments with a Viking Age / Medieval furnace which in his opinion has been used in the first stage of a two-stage process. Here the ore was first converted into slag with a high content of iron, but no metallic iron. In the next stage this slag is processed in another or in the same furnace where the actual conversion into metallic iron takes place. Arne needs help for his experiments.

Jan Jennisen, Netherland will build a typical shaft furnace with slag tapping of the type found in the Netherlands (Veluwe). This is the same type that Thijs van de Manakker uses.

Apart from theses experiments there may be enough participants to make experiments with other types for furnaces. No one has made an experiment with the Eastland furnace from Norway. Is anyone willing to try?

People from our own iron smelting group will experiment with the Drengsted furnace using wood as fuel. We have been working with this type of furnace since 1994 and are getting good results, but we still have not quite reached the stage where we can say that we have found the perfectly convincing way of running the furnace. We hope to get there during the seminar.

We hope to create a possibility for analysing the results of the experiments. Therefore we will try to have the ore analysed, and we would like the slag from each experiment to be weighed and sample for analysis. Also the iron should be weighed and analysed in order to give the best opportunity for a comparison with the archaeological finds.
Thisted Museum alone cannot carry the burden of having all these analyses carried out, so we hope for help from those who have good contacts to metallurgists and others. By joint effort we hope to succeed.

From Tuesday 29.04 - Sunday 4.05.


Tuesday29. 04 : Arrival and accommodation during the day
Construction of furnaces begins
18.00 : Dinner
19.30 : Welcome and introduction of participants
21.00 : Coffee

Wednesday30.04 : 8.00-9.00: Breakfast
Allocation of space, formation of groups, building of furnaces
12.00 : Lunch
18.00 : Dinner
19.30 – 22.00 : Presentations

Thursday01.05 : 8.00-9.00: Breakfast
Building of furnaces, iron smelting
12.00 : Lunch
18.00 : Dinner
19.30 – 22.00 : Presentations

Friday02.05 : 8.00-9.00: Breakfast
Iron smelting, primary forging
12.00 : Lunch
18.00 : Dinner
19.00 : Excursion to the North Sea at Agger. “The Black Man”
21.00 : Presentations

Saturday03.05 : 8.00-9.00: Breakfast
Iron smelting, primary forging
11.30 : Lunch
12.00-16.00: Open to the public, iron smelting and primary forging
18.00 : Dinner

Sunday: 8.00-9.00: Breakfast
Iron smelting, primary forging
12.00 : Lunch
16.00 : Cleaning up the area.
18.00 : Evaluation
19.00 : Dinner and farewell party

Monday: 8.00-9.00: Breakfast
Departure after breakfast

During the whole seminar there will be free coffee and tea.
Around 15.00 there will be cake or the like for the coffee break.



19.00: Martin Winter Olesen, from Herning Museum: Presentation of finds of Early Iron Age furnaces from the Herning area.
The furnaces have slagrums underneath the furnace, and some of them are built into a house, together with anvil and forge.

19.30: Arne Jouttijärvi:
The metallurgy in Martin W. Olesen`s project.

20.00: Jake Keen, Great Britain;
Agaria smelting in India. From Jake’s journey to East Asia, visiting early iron smelting places.

20.30: Darrel Markewitz, Ontario, Canada:
The Viking Age site at L'Anse aux Meadows (Vinland) and what is known about it in terms of the iron smelting there.

22.00: Arne Espelund: Bloomery smelting as a two step process?
Based upon theory, finds of slag at bloomery sites and the quality of well preserved and representative blooms a discussion of bloomery smelting as a two-step process will be initiated.


19.00. Arne Espelund: Calculations of output.
For an archaeologist, confronted with a slag heap, it is natural to ask: how much iron was produced here? The experimenter will rather ask: how much iron can be won from, say 10 kg of ore?

Iron in the ore will serve two purposes: provide a source for the metal and besides flux the gangue materials, above all Si02. Manganese, present as Mn0, will likewise flux the silica, while the remaining oxides simply will dilute the slag.

As the slag is composed of mainly Fe2Si04, only an excess of Fe0 can be reduced to metal.
Therefore only an ore with a ratio Fe0:Si02 > 2 (in molar proportions) can result in any iron. (As 1 mole of Fe0 weighs 72 g and 1 mole of Si02 60 g , divide the two values in weight % with 72 and 60, respectively).

Provided we have the analyses of the ore and the slag, we can follow the four elements Fe, Si, Mn and Al from the ore to metal and slag. A prerequisite is representative analyses. I prefer to use 10 kg of slag as a basis. By means of two equations you can determine the two unknowns ore consumed X and metal produced Y.

2. The quality of ancient blooms
In Norway some 20 blooms of medieval character can be found in our museums,
beside there are a handful of blooms from the Early Roman Age. The dating has been arrived at by means of careful studies of the remains of furnaces, lately confirmed also by 14C-dating.

The identity of a primary bloom has been determined by 1) density measurements – giving values from about 5.5 to 6.5, in contrast to the true density of iron 7.8.
2) shape: A medieval bloom are like a French cheese, from which a sector has been cut, with an external diameter representing the interior of the furnace, perhaps also a depression as a result of a primary smithing with a wooden pole inside the furnace.
3) metallography, including chemical analysis: the blooms are practically slag free.
Most of the iron produced was a mild steel, some times with less than 0.02% C.

From my point of view, it is not justified to name a mixture of slag and iron a bloom.

20.00: Leif Stark, Tranamo, Sweden:
Järnprocessen. The iron process.
Kolning.: Making the charcoal
Rödjord. The ore
Smide: Forging.
Historik: Historical background

20.30: Jan Jennisen, 412BC iron maker, Netherland:
who I am,
the place where I do my experiments (Archeon)
which types of furnaces I have experience with.

21.00: Peter Hambro Mikkelsen, Moesgaard: Fuel for thought: Straw and wood in slag pit furnaces

21.30 Jens Jørgen Olesen: The use of wood in the Drengsted furnace, our experiences.

22.00 Arne Espelund:
Jens Jørgen Olesen arranged on Oct. 28th last year a full day of smelting, which I could attend. We used an ore, which was analyzed and measured the consumed amounts of ore and charcoal. Slag was tapped and analyzed, and a piece of the metal produced studied by metallography. The experiment will be discussed in detail, with emphasis on the results, expected and obtained.

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