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Overview
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

Experiments in the creation of iron using Viking-Era Norse techniques

This section of the site will showcase the experimental smelts we have made. These expeiments are based on archaeological evidence, and are targetted to recreate the techniques the Viking Era Norse used to smelt iron. Our lead experimenter has also done a number of smelts outside of his work with DARC. To view his records of the various smelts including some more complete roll-up information please visit his page here. To jump directly to our smelts please use the menu on the left.

We get a number of emails asking why we make some of the choices that we do in our experiments. This can best be explained by providing a background on what we are doing and why. This section of our website records a sequence of experiments designed to bring us eventually to an understanding of at least one method the Viking-era Norse could have used to produce iron. There is, of course, no way for us to prove that the method we eventually produce was used. Our goal is to get a method that first reliably produces iron, and second uses equipment that would have been available and, third that matches the archaeological record that we have with regards to blooms produced, smelter and surrounding area layout, and materials.

Our research shows that there are at least three main types of smelters that would have been used. Rock slabs, some with clay/ceramic on them, have been found in a smelting context. This may indicate that the smelter was made of rock, or that it was surrounded by these slabs of rock. Similarly there are cobb (clay / sand / straw mixes) remains of what are likely smelters. Finally there are the remains of sod smelters from Iceland. Within these physical types, there can further be a range of sizes - diameter normally being all that can be ascertained from the remains.

At these sites we find charcoal remains, and slag (the left over bits that come from making iron), some iron ore, and - extremely rarely - an actual iron bloom.

We are coming to understand the physical relationship between ore, furnace, and charcoal. For any given ore body, there will be a best possible ore particle size, charcoal fuel size, and furnace design. The layout of the furnace is further effected by the nature of the material used to construct it. Air volume drives the complex chemistry and the physical environment inside the smelter. Unfortunately, no actual air delivery system survives from the dark ages, but the layout of the furnaces indicates some kind of forced air bellows system must have been used.

Extrapolating from blacksmith's work this implies that they used a bellows powered forced-air & charcoal system to turn the ore into iron.

Our first sequence of experiments were designed to test various bits of equipment while getting us to a point that we could reliably make iron. Once we obtained iron on a regular basis it was easier to adjust a variable in a smelt and understand how each might effect the overall progress and end result.

We often get teased about our use of mechanical blowers rather than bellows (although we have used various bellows systems many times). Air delivery remains the biggest question surrounding the actual Viking Age methods. Using a mechanical blower allows us to fix the amount of air moving into the smelter without having to worry about operator fatigue, different operators producing different levels of air, the changeover between operators causing a cooling, and so on. We have experienced all of these problems from time to time when we used bellows. Currently we are looking at trying to rigidly control the air flow to allow us to sort out some other variables. We will eventually return to the bellows before we complete the series. It is worth mentioning that this sort of experiment is often more difficult than people realize, often in very subtle ways. The bellows is a good example of that. To begin with there are no surviving examples of norse bellows. This means that before we can use them we need to figure out what they looked like. There are, thankfully, a couple of carvings of bellows, although these re blacksmith's, not iron smelting, equipment. Both are very simplistic but it is possible to see that they were using a two lobed bellows like you will see in our pages. They do not, however, come with good measurements. Since the size of the bellows directly affects the amount of air produced this is an important question. Many tiny things about a bellows (hinge method, height off ground, total lift on the lobe, size of air input, size of air output) can all impact the pressure and amount of air delivered to the smelt. If you don't know how much air is needed how can you make the bellows to produce that air?

We originally began with this list of variables (list will be added soon). Now thanks in part to our own work, and in part to that of many other experimentors we are confident that we can step out and make iron whenever we want. The next step is to modify that process to bring it in line with the known archaeological evidence. It is important to note that in many cases other experimenters have worked on these same problems. It is important for our understanding of the iron smelting process to often duplicate other's results to build our own direct experience.


In 2008 that will likely involve the following experiments. Two main variables will be examined: ore types and air delivery.

Test 1 - Multi-bellows air flow
Our consistant rate of air for the certain production of iron has been around 600 - 800 L/min. Yet a single Viking Age blacksmith's bellows made to our best guess of the correct size seems to produce a flow rate closer to 150 L/min. Needless to say this is troublesome. We have a theory for ganging multiple bellows together to allow a consistant airflow of the required rate. This (non-smelt) test will let us know if it would work.
Test 2 - Prototype 'Über' bellows
Another method for producing higher air volumes is scaling up the norse blacksmith's bellows. Our first attempts June 05 / September 05 / September 06 exposed many design problems. These large bellows would be re-constructed in light of what was learned in attempt to produce an effective design. A medium duration (not smelt) test measuring air flows will let us test this possible system.
Test 3 - prototype foot powered bellows
Based on arne espelund's evaluation of the 1750's evenstad document, another possible high volume air system is possible. This pair of single action bags is long and narrow and features a spring pole action, with the operator standing on the plates to power it. A medium duration (not smelt) test measuring air flows will let us test this possible system.
Smelt 1 - Ore Analog test
We have run a number of smelts with available ores. This has includes bog ore, virginia rock ore (of varying qualities), commercial taconite pellets, and hematite blasting grit. The varying ore qualities and sizes have had a range of impacts on the smelts. We are going to try shifting to an ore analog made by mixing the hematite blasting grit with a commercial clay. This should give us a fixed ore quality, with a standard nodule size. If this first smelt with these materials works we will run future smelts on this analog while eliminating different variables. For a table of materials we have used see here.
Test 2 - Multi-bellows air flow
Our consistant rate of air for the certain production of iron has been around 600 - 800 L/min. Yet a single blacksmith's bellows made to our best guess of the correct size seems to produce a flow rate closer to 150 L/min. Needless to say this is troublesome. We have a theory for ganging multiple bellows together to allow a consistant airflow of the required rate. This (non-smelt) test will let us know if it would work.
Smelt 3 - Reduced airflow smelt
Another possibility based on the norse blacksmith's bellows is that it is in fact possible to conduct a successful smelt with lower air volumes. This smelt will be to see if we can produce a bloom (and what it looks like) with an air-flow in the range of 400 L/min. This may require a couple of attempts to understand the working sequence (adjusting charcoal size, and ore size).
Smelt 4 - Further reduced airflow smelt
Assuming we can get a 400 L/min smelt to succeed we will retry at 200 L/min. (This closest to the volumes produced by a single norse double chamber bellows). This may require a couple of attempts to understand the working sequence (adjusting charcoal size, and ore size).
Smelt 5 - Multi-bellows smelt
Dependant on the results of test 1, a full scale smelt would be mounted incorporating all Viking Age elements. We would most likely run this smelt at an SCA event using many people to run the ganged bellows. As well as 'proof of concept' this experiment would also serve as a test of presentation and participation methods in a public demonstration.

Series two - icelandic sod smelter
Working with kevin smith, a new experimental series is being started, leading to a full scale historic re-recreation of the Viking Age iron smelters from the site at Hals in Iceland. This will include determining how to build an Icelandic sod smelter and then fire it with a high volume electric blower to see what we get. This is expected to require more than one smelt to effectively deal with a range of new variables.

If you have any questions about our smelting experiments please email us.


Royal OakWe would like to express our thanks to Royal Oak who has assisted us in these experiments with their generous donations of charcoal.


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, 2006   Copyright details
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