The Limits of Experiment

This outline was originally prepared in Spring 2004 - with only TWO experimental smelts to draw upon.
The following lists a number of considerations for the ongoing experiments into Viking Age iron smelting being undertaken by members of the Dark Ages Re-creation Company. In some cases answers to the questions posed are known, either through research into other experiments, or direct personal experience by DARC. In all cases the list details the range of possible variables.

RESEARCH

Smelter types: Note that these are 'invented' types, may not conform to current research definitions

- Ancient open bowl
Requires specifics on size, air system.
Research on rough spread / date sequences.
Special attention to Celtic Iron Age in Europe.
- Roman Tall Shaft
Suggested as passive draw system.
What is rough spread / date sequence - especially end of use information?
- Norse Boxed Short Shaft
Suggested by LAM, Norse double bag bellows.
Needs better definition on size and use sequence.
- Early Medieval Short Shaft
Suggested as starting in Spain via Arabs circa 700 and travels north.
What is spread / date sequence - especially into Northern Europe?
- Later Medieval Tall Shaft
Requires specifics on size, use of great bellows.
Comparison with later Evenstad documentation
Research on rough date sequences.

Bellows:

Survey of other experiments for data already determined.
Require documentation of rationalization of current reconstruction.
Use of two carved sources - are these the only information from artifact?
Evaluate problems with illustrations.
Rune stone is top view with no comparison object for scale.
Church is side view - but what is true relationship of bellows / human figures.
Relationship of inlet to outlet sizes.
Effect of valves - if any are used
Artifact basis for outlet tube sizes and construction.
Are variations on current design required?

Smelter Design :

Survey of artifact record for data that may be recoverable.
Survey of other experiments for data already determined.

What are effective ratios of : interior base diameter
interior height
interior throat diameter (taken together determines taper)
What is effective wall thickness related to : size ratios above
variation by material used
What is best composition of wall materials : clay type (Period use is local or specialized?)
mixtures - clay / cob / grog
What is most effective design of air inlet : diameters (Is there artifact evidence?)
projection distance to inside (or melts off?)
entry angle
positioning (related to base / slag tap)
What is most effective design of slag tap : size
positioning (related to base / air inlet)

Charcoal

What is the most effective particle size based on theoretical and other experiment results
What is the comparison between types and energy production
What is the relationship between types used historically and location / effectiveness

Process / Sequence :

Determine theoretical amounts via equations based on current materials and methods
Establishment of solid methodology for record keeping and assign team
- investment in other instrumentation? - sources / funding
- thermocouples?
- video recorder
- modification of smelter design to provide data - required?
(Note - optical pyrometer was purchased and is available for this year)

What is our OBJECTIVE for this years experiment :
- effect on overall equipment design

PRACTICAL

Blower Design :

Record of past experiments - air flow rates / air blast pressure

What equipment is available - strengths and weaknesses

What is best choice for this years experiment - VOLUME or PRESSURE (argument!)

Charcoal:

Possible modification of particle size based on equipment chosen
Consideration of manufacturing other type (note considerable effort required)
(NOTE - we have enough Royal Oak on hand for one more experiment)

Ore

Are we going to proceed with Virginia rock ore / effect on equipment
- are we going to reprocess gromp from previous experiments
- is it possible to source bog ore / effect on equipment
(NOTE - we have enough rock ore on hand for at least one, perhaps two new experiments)

Smelter

Ensure that structure is not destroyed at end of experiment :
- Suggested that weathering of structure may provide valuable information related back to archaeological remains.
What materials are available : how does this effect overall design

Sequence

Suggested that basic process worked out last year was generally successful:
We need to ensure that all aspects of process are recorded

Assignment of 'special teams', with team leader responsible:
- Logistic Support (2 minimum) day before and day after included
- awnings
- supplies
- support equipment
- Team Support (two required)
- watering and feeding individuals
- Record keeping : (two minimum) ensure that segments fit to master narrative
- timed notes (from zero hour)
- photography
- instrumentation
- Charcoal (two minimum)
- break up fuel to determined size
- measure charges to determined (recorded) sizes
- Ore Preparation (two minimum) must start early Sat AM
- prepare fire and roast ore
- gather roast and break up to determined size
- Smelt Process (two required)
- physical conduct of experiment
- Experiment Closer (one required)
- to ensure final aspects of shut down are orderly
- Evaluation (two minimum)
- general observations from all teams - RECORDED
- processing of experiment site (photos/ measurements)
- preparation of document

Equipment

Specific specifications of all equipment required for individual tasks needs to be determined.
Master list of requirements for all segments prepared
Ideally each team is fully equipped (no equipment sharing)