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Saturday, December 12, 2009

Objects - Authenticity Levels?

(This piece duplicated from 'Hammered Out Bits')
One of the things that all of us in DARC are struggling with right now is gathering the collection of objects we will need for our presentation at L'Anse aux Meadows in August of 2010. This is a major undertaking for the group, and we all want all aspects of our presentation to be at the highest standard possible.

Picking 'what they carried' is key to the image of the Viking Age that we will create. Objects define the characters and shape the activities undertaken. By serving as jumping off points for conversation, objects help mold possible discussions.

To avoid some confusion, often there is a differentiation made between 'reproductions' and 'replicas'. Reproductions are generally held to be duplicates of the artifacts as they now exist (partial or corroded for example). Replicas are generally considered to be a duplicate of an object when it was 'new'. Our interest here is primarily on replicas, be it duplicates of a specific objects, or something within a known type of object.
There are a number of criteria under which any specific replica object might be evaluated. This can get a bit confusing, as there is considerable overlap in the qualities expected, especially at the higher levels of detailing.
One set of considerations involves the general historical authenticity of a purpose made object. This primarily as assessment of the specific artifact prototype chosen :

Level One : Historic / Not Modern

This is perhaps so obvious that sometimes as a separate level it is disregarded. Here, obviously modern era objects are avoided and replaced with a sample from past history. An axe is used instead of a chain saw, a flame for lighting over electricity, clothing has the feel of 'costume'. Generally the combined effect of a collection of such objects is to leave the viewer with the impression of the scene being 'not modern day' but the exact historic period being represented may not be immediately obvious.

Level Two : Time Period

The object now will fit into the general types known from artifact samples from over the spread of the historic period of interest. A elements from a number of specific sources may be combined into one replica. An axe has a specific shape to head and handle, an oil lamp may replace a candle, clothing now has the feel of 'ethnic costume'.

Level Three - Cultural Set

At this point objects begin to draw on quite specific cultural prototypes. (Danish rather than Saxon for example.) There may be a narrowing of selection to reflect individual geographical locations. There will start to be a narrowing of focus to match the artifacts chosen against their specific functions. A combat axe as distinguished from a felling axe for example.

Level Four - Specifics

The last level is a bit harder to define, as it relates to quite specific narrowing of the artifact prototypes under consideration. Ideally, the choice would be all of A/B/C. In actual fact, it is often not possible to find an existing artifact that can fit all three characteristics. At this point, the detail of the persona characterization may become an important factor in determining the specifics chosen:

Level Four A - Date
Which may be extended backwards by 'heirloom objects'. The turtle brooches in Iceland a perfect example.

Level Four B - Location
Which may be extended by trade networks. Birka having a wider assortment than the backwoods of Iceland for example. Care needs to taken to avoid the obviously 'one of a kind' samples (See the 'Golden Buddha Rule')

Level Four C - Social Status
Which is often something that restricts the range UP - not as much DOWN. Even a king might use a wooden spoon! Most often this restricts overall quality and choice of materials, a brooch of simple iron rather than one of engraved silver.

A second evaluation can be made by looking purely from the standpoint of experimental archaeology. This is an assessment of the production methods used to create the replica. Potential historic accuracy of any object inside a living history presentation can be made on the following four point scale:

Level one is 'Form':

Here the rough appearance of an artifact is duplicated. This produces an object which is essentially decorative only ( a stage prop), and where the both the physical materials and production techniques used may be modern. Such an item will be acceptable when viewed from a distance of several feet. For example, most clothing used in historical presentations falls into this category - the cut may be loosely based on period types, but usually the fabrics are modern and sewing machines are used in the construction. Generally only the simplest of information may be gathered through the use of objects of this level.

Level two is 'Function':

Here the utility of an artifact is duplicated. Some care has been used to match materials and processes to match an existing artifact type. This item would be acceptable when held in the hand and would match the general performance in use of an original. A good example would be a hand forged axe properly heat treated and balanced. Although made using modern materials, there would not be a large difference in handling between these items and an original artifacts. Basic information about the characteristics of an object can be gained at this level.

Level three is 'Materials':

Here the original materials and production methods are duplicated, with special care made to duplicate the exact measurements of an individual artifact. A reproduction shawl made of wool and hand woven; with careful choice of colour and thread textures would be an example. Although it would not be required that the fleece to have been naturally dyed or hand spun, there would be no observable difference to indicate modern steps in the chain. The process of creating the object is now a source of information as well as that supplied by its actual use.

Level four is 'Processing':

At this point the raw materials themselves are created using period techniques, followed by using period production methods to produce an exact replica of a specific object. The item will be acceptable even using detailed analysis. At this level, the chain of production often becomes quite involved. For example, the production of an iron boat rivet (such as found at L'Anse aux Meadows) could involve recreating a charcoal kiln, processing bog iron in a bowl furnace to produce the iron rods, then finally the manufacture of the rivet itself using period styled forge and tools. Because of the complexity and scope of such experiments, the amount of data gathered is large and can often result in unexpected findings.

Applications :

When considering the objects to be included in DARC''s presentation at L'Anse aux Meadows in 2010:

Considering Historical Authenticity (Prototypes):

Every attempt should be to include as many objects as possible that exist at the full range of Level 4 (Specifics). Ideally all of date / location / status should be matched to individual characterizations.
(The original set of objects for LAM were detailed between Level 2 and Level 3, this primarily in an attempt to portray the wider range of Norse material culture.)

Considering Historical Accuracy (Production):

Ideally the majority of our objects will confirm to Level Three (Materials). Those demonstrating individual crafts specialties should endeavor to include some objects at Level Four (Production).
(The original set of objects for LAM were detailed between Level 1 and Level 2, with a selected few at Level 3. This primarily due to a quite restrictive budget.)

A possible third set of qualifications can be to sort objects by their effective contact distances. That is the distance where any differences from historic prototypes become obvious.

Across the room - 10 feet
During conversation - 3 feet
In the hand - 1 foot
Detailed look - 6 inches
Scientific observation - a magnifying glass

Steve Strang made an important observation, based on his experience working a number of different historic periods :
'Any object should have a level of authenticity which matches its normal observation distance.'
What he is getting at here is that differing objects are intended for different 'contact distances'. At a minimum there should be no easily observable modern aspects at that distance. A piece of clothing should have hand sewn seams on the outside edges, but any seams underneath are not observed, and can thus be modern machine stitching. A knife blade could be made of roughly polished stainless steel, as normally it is never placed in the hands of visitor. A drop spindle, which might often be placed in the hands of a visitor, needs to have a high level of detailing.

Generally this means that all our objects must pass observation at a distance of at least three feet (conversation distance) as a bare minimum. A very good number need to pass observation at one foot (in the hand). There may be some rare few that need to withstand observation at six inches (close to the face).

One last general guideline is from Bruce Blackistone - 'Uncle Atli's Bronze Buddha Rule' :
'No more than one really weird/exotic/semi-improbable item in the camp at an event; and it must have a logical, historical explanation.*'
* Such as: "This odd statue came from my uncle who traded for it in
Miklagard" NOT "When I ventured through China and Japan after being
kidnapped by Gypsy pirates, I became a Buddhist."
(Note: This is an expansion of a segment I wrote for 'Interpreting the Viking Age' in 2000. It should be considered to be FULLY COPYRIGHT material. )

Darrell Markewitz

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Monday, November 16, 2009

Vinland 3 on YouTube

Re-Creating the iron smelt by the Norse in Vinland, circa 1000 AD. Members of the Dark Ages Re-Creation Company ( undertake their third smelt in this specific series on November 7, 2009. The result was a 2.9 kg bloom produced from 18 kg of bog iron ore analog. This smelt used all human powered air, supplied via a Norse style double bag bellows.

Footage shot by D. Markewitz & K. Thompson

Iron Masters : Darrell Markewitz & Ken Cook
Charcoal : Sam Fallezone
Ore : Neil Peterson
Records : Steve Strang
Bellows operators : Dave Cox, Marcus Burnham, Sam, Ken, Darrell
Consolidation: Ken, Darrell, Dave, Sam

(duplicates post on Hammered Out Bits)

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Wednesday, October 14, 2009

Vinland 2 Smelt - On YouTube

This short sequence shows the mechanical piston bellows in operation (dubbed the 'FrankenBellows'). A sequence about 3/4 the way through the smelt, showing the effect of cracking from the clay slab construction used. Last is the extraction and first consolidation sequence, featuring Ken, Neil and Sam.

Cross posted from 'Hammered Out Bits'

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Tuesday, September 29, 2009

Pit Fire Pottery 1

Icelandic Althing Event, September 2009

Kary's project, with contributed pots by the group.

Some images of the extraction and the results.
All shot by Jo - on my camera.

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Wednesday, July 22, 2009

IRON Mandrils - Iron Oxide bead release?

"Ancient beads were often made on cast iron tapered rods, without the use of a separating agent. Once a bead was finished, the rod was heated to red-hot and plunged into a container of salt. This created a chemical reaction, causing the cast iron to rust and the bead could be easily tapped off the rod."

Quote from

(Note: In all fairness to Jhan, her interest lies in duplication of historic beads using modern flame working tools and methods. She clearly references that someone else told her this, so I am not critical of her otherwise quite good web site!)

First, what is being referred to here are artifact wrought iron mandrils. Two have been found in the Viking Age layers at Ribe, Denmark. (This is the focus of interest of Neil Peterson's experiments with DARC.)

As an experienced metal worker, I do want to stress the actual material. There is a significant difference, both chemically and structurally, between the various different iron based metals that might have been used. This also extends significantly to the oxidation rates.
I know that 'cast' iron was not used historically. This high carbon alloy was not clearly understood or widely employed for any purposes until into late Renaissance times (varies depending on location, much earlier in the East).
Most likely is some form of bloomery or wrought iron, the low carbon material most commonly used for all forged objects up till the Industrial age.
For comparison, modern mandrills are typically a nickel alloy (stainless) which basically did not exist until fairly recently (the Modern Age - say 1900). This material is used because of its great *resistance* to oxidation.

I have made up one actual 'wrought iron' mandrill, using antique recycled metal (on a guess from the late 1800's). This specific material most closely matches the bloomery iron that would have been available during the Viking Age. The form is (loosely) based on one of the artifacts from Ribe. The shaft is about 30 cm lng and is mounted into a wooden handle. The fairly heavy cylindrical body shoulders in near the tip for about the last 3 - cm. The diameter here is roughly 3 mm, tapering slightly to the end. To date we have primarily been using a fairly standard method of coating the working area with a clay resist.

I have reservations that the theoretical salt water quench method as described would actually work in practice. There are two primary forms of iron oxide in play here. Chemically these are Fe3O4 or Fe2O3:

The first (Fe3O4) is the high temperature form - black oxide or fire scale. It is hard, brittle, and adheres both tightly and strongly to the parent metal. Its formation is fast - due to the temperatures (above about 450 C or so). I just can not see this being of any value to the bead making process, as the glass strongly attaches to this layer, then due to the bond between the oxide and the metal, it remains firmly in place.

The second (Fe2O3) is the low temperature form - red oxide or rust. This layer is soft and crumbly, and breaks away easily under any mechanical pressure. Generally this is a slower formation, taking place at room temperatures. This process is accelerated (ask the chemists why) by water, and a bit more so by salt water. Now, it might be possible to use this layer as resist, as it does easily break free from the parent metal. This layer is certainly extremely thin. This presents two problems. First - there is not much separation layer to begin with, so it would be extremely easy to scrape it completely off and expose the metal underneath. Second - the layer is so thin that it conforms closely to the shape of the parent bar. The interior of the glass wraps tightly around any irregularities in the metal mandril. Although every attempt is made to produce a mandril with a perfect cylinder, or a slight conical section, one of the functions of a thicker resist layer is to lift the glass away from any imperfections. Such a thin layer as the oxide would create would just not give enough gap between metal and glass.

I should mention that one observation I have from forging actual wrought iron is that when it is quenched from incandescent in water, often a thin film of red iron oxide will form on the surface. As suggested, the quality of the iron does effect this. However, given the problem of creating a suitable 'release gap' I still think that this natural oxide layer is just not thick enough. Even with the slight acceleration produced though the use of salt water, the layer of Fe2O3 created would far to thin to be significantly useful here.

I suspect that this whole idea was theoretically reverse engineered to explain observations of a special situation. I believe (?) some glass beads were found to have a very thin layer of iron oxide in the interiors of the holes. How to explain this? Pair this observation with the discovery of a couple of wrought iron mandrils. Presto! A working method, now enshrined in the literature (although never actually tested). Repeat that WAG, until it has become an accepted method (still not tested).

An alternative : given the wide availability of various iron oxides as ochre deposits, perhaps a well known resist material was simple red ochre mixed with water as a paste. This applied just as we do our fine clay. This is a method that would be easy to test experimentally.

Additional tests:
- As Neil Peterson has mentioned, examine only BROKEN artifact bead fragments from production sites to check for the presence of resist. We know that the thin clay layer is fragile, and relatively quickly will clean away from the interior of any bead actually worn on a string. This does tell us beads found removed from production sites may not yield useful information.
- We tend to take a very long time to make a single bead. Historic production work is sure to be much faster. The way the clay interfaces to the glass is sure to be time dependent. Is there any way to check on this?

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      Updated: 4 Dec, 2007
Text © Dark Ages Recreation Company, 2007
Photographs © Individual artists
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