Tuesday, June 10, 2008

Heltborg Experimental Notes Available

Slowly but surely I'm trying to get my notes in order from the Denmark trip. I have just posted up my experiment data and field drawings on to the Wareham iron smelting section. Likely the easiest way for those interested to get access is just go on to the 'Overview' of the Iron Smelting Seminar at Thy I had mentioned to you earlier. If you wander down through the short descriptions, you will find the links to the drawings and data now included.

In case you missed it - what I undertook at the symposium were two experiments.

The first was working with Arne Espelund, on the two part ore - slag / slag - bloom theoretical process he has proposed (that we were discussing last week). You can take a look at the sequences and try to figure out what went wrong (!). I have some ideas about this, but have not written those up yet.

The second was an experiment to apply the 'North American' sequence to a blend of Scandinavian ores. I would not consider this entirely successful, even though there was some spongy iron produced. The yield at roughly 12% would seem to be in line with what the Danish teams often get, but certainly less than what is normally seen at home. The conclusion once again is that ore quality must modify smelting sequence, and to a certain extent furnace design.

Friday, June 06, 2008

Museums in Denmark

I had quite differing experiences with the various museums I saw in Denmark:

There were three museums I visited that were basically 'old school' styled presentations: Objects in cases, extremely limited labels, objects generally grouped by type. The lighting varied, but generally was reduced general illumination, with use of some spot lighting in the cases. Some idea of light levels can be gathered by the quality of the images. (I have some experience with longer 'hand held' exposures, so the clarity and shift in colour will give some indication of the relative amount of light available.) None of the museums I visited had any staff visible inside the collections themselves (admittedly I was there 'off season', but I also spent several hours at each museum.)

The National Museum in Copenhagen had its 'Pre-history' gallery closed. For them anything before 1000 AD is lumped together. This new presentation includes virtually ALL the Viking Age materials. It was originally scheduled for opening on May 1, but later delayed to May 17.
The Medieval galleries are very clearly old style. The concentration there was on church related pieces, many larger. The stress appeared to be more to 'treasures' rather than everyday objects. Labels were basic: Object / Location / Date - in English and Danish. Sometimes a line or two of context or more detailed description. No registration numbers (very rarely these were visible on the object itself) . If there were a group of like objects (commonly grouped by type) they would share the same three lines and have no further method of identifying them. ('Early Medieval Axes' for a group of a half dozen, obviously mixed construction and combat types) This would make any attempt to get more detailed information from the collection viewing almost impossible. You were not normally allowed to take photographs, and there were no detailed 'guide to the collection' type books available. (Separate topic discussing those.) The gift shop was large with an excellent selection of books ranging from popular overviews to quite detailed archaeological reports.
(Group of Early Medieval Axes)


The Roskilde Museum is actually a complex of related buildings and presentations, each with a different theme. I spent my time at the 'History of Roskilde' collection. The building housing the historic collections was originally a warehouse and factory from the mid 1700's, so there are a large number of small rooms with theme groupings. The objects generally were grouped by find location. Again labels very short (and here only in Danish) with Object / Find / Date. The individual pieces were more usually identified by case number, but again registration numbers were not visible. I'm not as sure here what the policy on photography may have been, as I was introduced to the collection by curator Jens Ulriksen. The gift shop was a small display in the lobby, with limited books available, few in English.
(Group of Blacksmith's tools)


The Ribe Viking Museum focuses quite clearly on two aspects of the history of Ribe, with the main thrust of the collection centred on the Viking Age. About the same floor space is dedicated to Medieval, Renassiance, Early Modern objects (with most stress on the earlier materials). Both the building and the presentation itself are more modern, and it shows in the display layout and methods. This unfortuneatly includes the use of dramatic spot lighting in rooms with a generally quite reduced light level (to the determent of possible photography. One excellent feature of the presentation was a full scale diorama of a section of the Viking Age market. This put a large number of the artifacts in a working context (and included a huge number of other pieces not represented in the collection.) I think officially there was not supposed to be photography, but I did see any number of general visitors taking photos. The gift shop was again large and had a fairly good selection of books, but here there was more space given to gift items. Popular works were generally available in English, unfortunately most of the research volumes in Danish only.
(Glass Working Display)
(Metalworking in the Viking Market scene)


My visit to the Viking Ship Museum in Roskilde suffered from a major renovation and my own focus on research of ship building tools. The room normally containing the supporting artifacts was closed, with a new exhibit documenting the recent production of the replica 'Sea Stallion' being installed. Labels were available in Danish and English, with usually a short paragraph of detail. One detail I did like was the working tools in the boat yard area (all replicas of course) were hung in public view. Each had Find / Museum / Registration number. The main ship hall has the preserved remains of a number of the ships on display, backed by detailed scale models for comparison. This hall has a large wall of north facing glass, so photography was simplified (and permitted). There was also a room with walk on reconstructions of two of the ships (primarily intended as a children's activity room. Much of the complex is given over to the docks, the boat construction yard - with the large number of replica ships and boats floating and in use. As outdoor areas, the photography is excellent, outside of the restricted viewing angles. (see an earlier post for ship images). The gift shop here had a very good selection of both popular and research titles, many available in several languages. Most of the detailed research volumes were related to ships (unsurprisingly), but many of those only in Danish.
(Working Tools - some of the axes)
(Children's area with full scale dressed replicas)


Generally I found all the museum collections I visited had greatly reduced information available to the viewer. In many cases only the barest description was provided 'bunch of axes' being typical. Sometimes the objects were not even given enough description to provide real understanding, for example 'spindle whirls' does not inform you about just what those pieces are. With no registration numbers, it would prove very difficult for the research minded to gather detailed information. Rarely were objects placed in any kind of working context. The collections were almost all presented in a formal and static style (Victorian Cabinet of Curiosities). The Viking Ship Museum was the primary exception, but it blurs the line between artifact collection and an experimental archaeology presentation (which in fact are in two distinctive areas of the complex).

I also spent two afternoons at the Ribe Viking Centre, a living history styled presentation. As this museum was not officially open at the time, and also represents an entirely different type of display style, I will leave a discussion of it for another entry.

Thursday, June 05, 2008

Photography in Museums

This piece was spawned by a discussion between Neil (who just got back from Iceland) and another correspondent (who asked that the entry to be edited from the version originally posted at about 9 AM this morning). My comments took on an (overblown) life of their own...

(Neil's original observation)

1. Allow photos - bluntly get with the modern world and
allow it.
The concept of "we copyright our artefacts you can't take
pictures but we'll sell you..." is dead. The "it interferes
with other people" in most cases isn't true. I would have
said "never" but after Maeshowe I'll moderate that to
"mostly". Even in the case of places like Maeshowe there
should be regular "photo tours" where photos are allowed
(say 1 of the 8 daily tours).
Feel free to disallow flashes, feel free to use anti-flash
glass. Feel free to keep fabrics in drawers with the lights
off until people pull them out and push the button.
This goes further though - people want the photos so HELP
them. Check the lighting for glare on the glass. Provide
scaling in the exhibit cases so the photos are more useful. Perhaps the simplest way is just to use a standard font to
provide the numbers in the cases. A couple of museums did
that, now I just have to email them and ask what font it was
and presto I've got a scale.


This is a massive problem, going back to the late 70's into the early 80's. By my observation, about the same time as the switch from museums regarded as collections held as a public trust headed by historians and archaeologists, to museums as entertainment enterprises headed by business managers.

When museums were supported by public funding, a clear argument can be made that the owners of the objects are in fact the visiting public. I therefore have a right to take images of my own stuff. Tempered by the dynamics of maintaining public access and not harming the objects.
I find the general idea that many major museums consider that allowing images to be taken of objects inside the collections is to be considered a form of revenue generation troubling on a couple of levels.
Right off the top, I must temper my opinion by noting that particularly in the United States, there are many PRIVATELY owned collections, rather than the mainly PUBLIC ones normally the case in Canada. There is a further gray area around 'Not for Profit Corporations', which are also far more common in the USA than here in Canada (and I suspect not common in Europe either).
I note that when an institution says it is 'licensing images from the collection' this implies (to me anyway) that it is the likeness of the object that is being controlled, not the physical photograph itself. If the object is held in a public institution, the museum is at best 'holding the object in trust for the public' and a legal argument can be made that 'they' do not actually 'own' the object itself (see above).

Commercial 'for personal profit' use of the images being perhaps a different situation. I say perhaps. There may be a fee charged which is related to the mechanics of making the image itself. Note that this is not related to the 'rights' to the actual object.
If I request the object taken out of its case, so that I can apply special lighting or image set up, then I should fully expect to pay something for that level of access. In this case I am paying for the supervision and action of the curatorial staff. However, as I personally make the actual photograph, what I chose to do with it after the fact is my concern alone.
If I want to use a 'standard image' that the museum has produced of the object (where they have done that set up), then of course I should have to pay for the service provided. Then I am in fact paying to license the photograph itself. This costs whatever the institution deems suitable. Again its not the likeness of the object, but the physical photograph I'm then paying for.

There are clear technical restrictions related to objects and photography.
- The most obvious one is related to the use of lighting. Without direct staff supervision, no use of specialized lighting. This extends into the public displays - no use of flash photography by anyone, at any time, of any thing. It is true that only certain classes of objects react in a negative way to intense light, some are not effected in any way what so ever. Painted versus metals as a clear example. For purposes of control, its just simpler to rule 'no flash photography'.
- No use of tripods (or monopods). Two reasons, the most obvious being the blocking of floor space that tripods represent. The second reason was originally related to image quality. In the days of slow films, it was simply impossible to make 'publication quality' photographs without the use of a tripod during the exposure. The way to solve this physical limitation imposed by the technology of film cameras was through the use of flashes. See above.
So in the 'old days' a simple way to segregate personal 'snap shots' and potential commercial photography was simply to forbid the use of either tripods or flashes. However, starting in the late 1970's technology started to breach these imposed limitations to quality.
- First was the introduction of more sensitive colour films. I can actually remember when the first of these, Kodak Ektachrome 200 ASA, was released against the then standard Kodachrome 64 ASA. At first this increased ability to take effective colour images in lower light was balanced by less clarity to the grain. Eventually most of the major manufacturers had colour print and slide films that gave accurate colour and high image quality at 400 ASA. This the difference between needing bright sunlight to being able to shoot good images with normal indoor light levels. (Refer to the comments on museum lighting below)
- The Second 'problem' for museums was the introduction of physically ever smaller and more automatic cameras, especially as built in flashes became the standard. Again in the 'old days', a quality 35 mm camera was a relatively large and complex piece of equipment. The flash itself was a secondary piece of equipment. These were bulky enough to be clearly obvious. So museum staff could sort out potential commercial photographers at the gate. These were also significantly expensive equipments - a good 35 mm camera cost the equivalent of at least three weeks wages. The standard 'instamatic' type tourist camera took small and extremely poor quality images, certainly not good enough for any kind of publication use. As camera technologies and miniaturization increased, better image quality and more automatic features got packed into smaller packages - and at seriously reduced prices. A major problem now occurs. The camera is far smarter than the person using it. The machine decides if a flash is required, and uses its own built in flash to provide the intense light required. Most owners have no idea how to turn off this function. It becomes easier for museum staff to just forbid ALL cameras than attempt to judge just who is knowledgeable enough to be allowed to use one correctly in the museum environment.
- The switch from film to digital imaging has huge implications. The 'processing gap' between taking the photograph and converting it for publication has shrunk (if not completely disappeared). My current digital camera is an Olympus 35 mm frame with a 8 MG 'sensitivity'. The cost was roughly equivalent to one and half days pay. The images it takes are roughly equivalent in terms of quality to those I got from my 30 year old Yashica using Ektachrome 400. Now I took over 600 images on my recent Denmark trip. At two museums, I took images of virtually EVERY object in the collection from the Viking Age period. If I had done so on slide film, the cost of film and processing would have been at least $600. Most of these images are at least good enough quality for web based publishing. I was not using the best quality that the camera was capable of recording, but even still most of the images would compact to the standard 300 dpi at 8 x 10 size (again about what would be expected from the film).

Curiously (or not so much so) the increasing use of 'theatrical lighting' in museum presentations also have its date traced directly back to the increasing technology of casual photography. Many of us who love detailed looks at objects remember the old days of the 'Victorian Stuff' museums and display methods. Flat groupings of many related objects with simple and ample overhead lighting. One easy way to reduce the quality of potential images is merely to reduce the amount of light available for making the photograph. Some of this shift is also due to an increased consideration for the durability of some objects and the effect of light on them. When the case is full of iron or glass, this argument is laughable however. The current use of small pools of highly directed lighting clearly negates the argument that this is done for preservation alone. Any serious student of the artifact has been endlessly frustrated by the net result of such theatrical effects. A highly illuminated surface that leaves the rest of an object shrouded in darkness leaves the human eye unable to make clear observation. It certainly makes clear photography virtually impossible, and its hard not to assume this is the primary reason for the staging.

On my own recent trip to Denmark, I had contacted each of the major museums I planned to visit well before my departure. The most important net gain to me was that each institution allowed me to take photographs inside the collection. For at least two of the museums (National Museum in Copenhagen and Ribe Viking Centre) there is normally no photography permitted. At the Ribe Viking Centre, I did in fact take images of virtually their entire Viking Age artifact collection. I also purchased both the popular overview and the primary archaeological report containing 'official' images of the same objects (spending some $200 just on these).
I balance that very positive experience against what happened at the National Museum in Dublin on my only other overseas trip (back in 1989). Here I was not even allowed to take my camera INTO the museum. This because they were attempting to generate revenue via the selling of books that described 'the Treasures' - objects like the Ardaugh Chalice and Tara Brooch. My reason for visiting the collection was NOT to see these objects (for which I did in fact purchase both books and 'official' images on slide). My interest was in the many everyday (thus not 'impressive') objects from the recent Viking Age Wood's Quay excavations. Objects which (even still) have largely not even had the original primary archaeological reports published. The net result was that instead of any clear record of what was on public display, I have merely a few scribbled notes and small drawings in tiny note pad. On any number of levels, the entire experience was negative.


How fast the once imposed technical limits on photography are shrinking creates new problems for any institution that operates under a pure business model, where they think access to quality images of their collection is nothing more than a revenue stream. Truth is, many institutions are allowing the imaging technology of the 1970's and the business practices of the 1990's to shape their current policies.
At best, a policy of 'no photography without signed release' is one that would satisfy both researcher and manager.

Monday, June 02, 2008

Tranemo Team Bellows

If you are a regular reader, you have seen an ongoing discussion of my own re-creations of Viking Age blacksmith's bellows. The air that is delivered to the smelter is one of the most critical elements of the process. The total volume against time, the pressure of the flow, the position of the air pipe - all can have dramatic effects.

One of the things I had really wanted to do at Heltborg was get some numbers on air volumes. This is one of the most poorly recorded of all the variables that various experimenters have to work with. Partially this is due to the extremely wide range of types of air delivery systems individual teams make use of.
I had made a serious attempt to record actual outputs using my small hand held aneomometer. This gives a reading in kilometers per hour, through a standard 2.5 cm diameter hole. A little math converts that number to litres per minute. Unfortunately, it soon became apparent that the meter was not functioning correctly. The measurements were proving too inconsistent (the same power reading would produce quite different air flows on repeating the test).

The Danes especially all use pretty much the same commercial vacuum cleaner blowers. (Now the comments about 'vacuum blower smelters' makes more sense!)This image is of the equipment Michael Nissen lent me for my own three smelt experiments. The 'Nilfisk' blower is hooked up through a variable transformer to control motor speed. Remember that all the power in Denmark is 220 volt. Measurements are made using an output power meter on the downstream side.

The other air system I was quite interested in measuring was the 'traditional' great bellows (double bag system) used by the team from Tranemo. I only have this image of the bellows, taken on Tuesday as the team was still setting up. (I had shot a long video sequence of the bellows in use during a later smelt. My camcorder died on me half way through the week - and the tape is jammed inside unable to be removed. Don't buy a CANON!)
I did make measurements of the system in use:
Earlier, Neil had set up one of those 'Google Spreadsheets' which allows users to plug in a series of basic measurements and get a * theoretical estimate * of air volume produced. (Go HERE to see the table)
I had good numbers on both the dimensions and the pump rates. I did have to make some WAGs on the two efficiency numbers. The loss at the valves was considered to be minimal. This bellows used rigid flap valves set on the underside of the bottom plate.
Still, the potential air volume from this bellows is in the high end - a potential at 1380 litres per minute (at the roughly 12 strokes per minute rate I observed.) Given a fairly standard 25 % working efficiency from the theoretical number, that brings the working volume produced to about 1035 LpM.
The smelter itself was 30 cm diameter, so using the Sauder & Williams method numbers (1.2 - 1.5 L/cm2) the required air volume is projected to 850 - 1050 LpM.

Now of course, in use the variable that iron masters pay more attention to is actual charcoal consumption rates. How fast you burn a standard measure of fuel. Hopefully at some point, the individual smelt data reports for the various Heltborg experiments will become available so there can be a comparison made between the air rates and the burn rates.

Saturday, May 31, 2008

Viking Ships at Roskilde

(Repeated from the DARC blog)
Today is smelter prep / workshop day for DARC, against our upcoming spring smelt on June 14. So I wanted to get my presentation version of my Denmark images sorted out and transfered over to DVD. At this point I have taken the various panoramic images I shot and patched them together. As a bit of a break from my concentration on iron smelting here, I have posted a couple of images from the Viking Ship Museum in Roskilde.
View of the interior - Note that the ship is tied to the dock on the STARBOARD side.View of the hull at the waterline on the port side
The first are two views of the 'Ottar', a reconstruction of Skuldelv 1. This is a knorr (knarr over here), an ocean going freight vessel. The original was built in Sognefjorden Norway. This is the hull that Paul Compton's 'Viking Saga' is based on.
The specifics from my notes:
length - 16.5 m
width - 4.5 m
capacity - 20 tons / 35 cubic meters
draft (laden) - 1.3 m
sail speed - 12.5 knotts (empty?)
construction - Denmark, circa 1030
View of the interior, this ship tied 'to port'.
The last I am pretty sure is the reconstruction of Skuldelv 6. This is a medium sized coastal working ship for fishing or trade. There were a number of boats at the museum dock on this basic pattern These are obviously the work horses of the sailing programs there.
The specifics (from the text):
length - 11.2 m
width - 2.5 m
capacity - 3 tons
construction - Norway, circa 1030

I got more detailed in my notes with the other museums I visited. I had wandered over the dock area before the museum opened in the morning to take these images. My main focus at the Viking Ship Museum was actually on construction and especially working tools. (This related to an ongoing project for Parks Canada to produce a complete set of Viking Age ship building tools.)

Wednesday, May 28, 2008

Norse Welding Flux?

As you may have seen, I started Hammered Out Bits mainly as a means to record and share the longer e-mail responses I was sending out almost one per day. Although the information contained below may be well known to many of the metalsmith readers, I figured I had the piece already written...

"... I am a 14 yr old student who is studying vikings. I am trying to find out what the vikings used in order to weld. I cannot find it in any of our libraries books. I know that the modern blacksmith can use borax. Did the vikings use this or something similar? "

Thats a pretty good question:

Borax is commonly used by * modern * and * north american * blacksmiths. Its what I use in my shop here. There are a couple of different versions available. You can purchase a product called 'Easy Weld', which is borax mixed with iron filings. The wee bits of iron dust make the two pieces you want to join tend to stick together quickly, but also leave the welded surfaces covered in lumps. So this stuff is ok for big structural work (or for a horse shoe) but not any good for finished work (say like pattern welding on a sword).
You can purchase chemically refined (water removed) forge borax. This stuff works great, but its pretty darn expensive (although you don't need very much). At something like $50 a kilo its more than I want to spend.
I use plain old washing borax from the grocery store - like '20 mule team'. This has the water still in the chemical, so it bubbles up a lot when applied to the red hot metal. But its also cheap, at something like $5 for a 2 kg box.

Now - borax is a chemical that only occurs around some specific dry lakes usually found in deserts, where the water evaporates and leaves the powered chemical behind. None of that in Northern Europe (that I know of?).

The tradition in England, and in Denmark (at least) is to use a fine while silica sand. I know smiths still working in both countries that still use sand as a flux when welding. I must tell you that I personally have not ever done this! What I have been told (and it fits the chemistry) is that the metal needs to be hotter before the sand flux is applied (higher melting point for silica) than would be used with borax. This suggests more skill for the smith.

The reason here is that the purpose of the flux in the first place is to seal the surface of the bare metal from the effects of oxygen. The iron oxide, a dark scale, that forms on the metal surface when heated and exposed to oxygen, will not weld. So you would want to carefully watch how much air you blew into the fire, then very quickly pull out and apply the sand flux to seal the surface.A classic forge welding image. The bright sparks are actually droplets of hot liquid slag being forced outwards under the hammer stroke.

Then when the metal pieces are heated further to the correct temperature (a bright yellow to white) they are quickly moved to the anvil and stuck with the hammer. The series of blows have to overlap, moving from the centre of the pieces towards the edges. This compresses the joint to squirt out the flux between the pieces. Hopefully the now liquid flux also lifts away and washes out any oxides or dirt that may be between the pieces (or you get a failed weld). The trick is to hit hard enough to squirt out the flux and compress the pieces to fuse them, but not so hard as to completely distort the very hot (thus very soft) metal. Oh - and do this all working darn fast - as the metal will cool from 'welding heat' in mere seconds.

Did I mention that your Norse anvil is maybe 10 x 10 cm and maybe 5 kg - or maybe even a rock? Different metals have different welding temperatures too. Makes you understand how difficult is was to produce a pattern welded sword in the Viking Age.

You might find some more information related to Norse and Saxon knives and their construction on the blog (below). I have an article on Viking Age knives I was working up also on line:

http://www.warehamforge.ca/norse-knives/

I would suggest flux for the Viking Age is most likely going to be white silica sand. I do note however that is is just the kind of thing that is pretty hard to state for certain. You would have to pour through chemical details on academic reports on the archaeology for any evidence at all - assuming any one has ever closely examined the question.

Welcome to the world of artifacts and archaeology!

Tuesday, May 27, 2008

DeMystifying Layered Steels

Josh wrote:
" Can you turn me on to some information regarding techniques I need to start forging layered blades. ... What {alloys} do you recommend and how many folds do I need to attain the proper bond before I forge the third steel to the others. I know 512 layers is the damascus requirement and need your advice on the specifics. Are you thinking about making a layered bladesmithing video? "

I started working on a new DVD - 'Basics of Layered Steels' back in winter of 2007. I own a VHC camcorder (and a half decent one). I shot about 2 hours of rough footage, some of it of objects now sold. It turned out the tracking is off on the camera and all the footage has a fold line through it and flips regularly. Not at all suitable for conversion to an educational program. And to top it off, no one will work on a 15 year old camcorder.
I have bought three digital cameras over the last year. All with problems - the last was a new Canon, but the power system completely crapped out mere days after the warranty period. Will cost as much to repair as to replace with a brand new one.

So the long and short is that I was working on a program on Layered Steels - but the whole thing is on hold pending equipment.

Josh's request shows some pretty typical misconceptions about layered steel. Much of what is written is incorrect or misleading. In one especially well known series of books on the topic, what is MISSING is more important than what is included. Too many smiths have taken the approach of framing their descriptions of their own work as mere advertising or even mysticism - merely to make for better sales!

As an initial starting point, take a look at my information on the Wareham web site (although elementary). I have also a number of past blog postings on various layered blades I've made over the last couple of years. (try searching under 'bladesmith' and 'knives')

Ok - this is the very quick (!) basics:

- the hard layer gives the cutting edge (durable but brittle)
- the soft layer gives the flexibility (soft but bends)
- the net result of adding soft to hard is to effectively REDUCE the edge holding - a straight mono blade of high carbon will always keep the best (hardest) edge, but at the risk of being too brittle.
- three layers of soft / hard / soft may prove the best balance of edge and durability (but its boring to look at)
- when welding, typically your outside surfaces should be plain mild steel. It takes more abuse, and is the cheapest material
- number of layers is only critical in terms of decorative effect. Low layers have few lines, generally less interesting visually
- remember that layer count goes up EXPONENTIALLY. A 2000 layer blade may only be one more weld from a 500 layer one
- remember that work effort should be counted by number of welds, not number of layers.
- extremely high (plus 1000) layers will suffer from 'carbon migration' effect (layers in effect blend together)
- I * personally * find the nicest patterns at about 250 to 500 layers (depending on method) - so 4 / 5 welds
- PATTERN WELDING (museum definition) is applied to twisted rod method (Northern European)
- variations in metal content react differently to acids, so are chosen for decorative effects
- etching can give two effects, shift in height (typically Nitric or Sulphuric) and shift in colour (typically Ferric Chloride)
-acid chosen may be determined by metal alloys in the mix

Personally, I tend to stick to the following construction:
-starting pile at between 9 - 13 layers (9 most typical) I usually have a long piece of mild steel in the centre as a handle
- I still like to wire the piles together for welding (just old fashioned I guess)
- two weld / draw sets - to about 50 layers
- at this point twist rods that will make up the back of the blade
- two layered blocks are welded to a piece of high carbon (for the cutting edge)
- Weld together edge and back pieces for the billet
- use L6 (.5% stainless about .5 % carbon) for decorative effect (produces thin silver lines)
- use wrought iron (antique) for decorative effect (produces 'rope' texture)
- etch first in Nitric, which changes heights of metal layers (topographic etch)
- etch second in Ferric, which brings out extremes of colour (surface effect only)

You can see a number of my past blades using layered steel HERE

The images are of my last blade commission (April 2008). This Viking Age man's knife is a typical seax type. Blade length is about 5 inches. The handle is a simple section of caribou antler.

The blade is pattern welded. In this case there are three separate twisted rods that make up the back. The edge is formed of two additional blocks welded to a high carbon core. The total layer count for the blade is 261.
I started with a pile of 13 plates. The mixture contains Mild steel / L6 / High carbon (1095 file) / wrought Iron:
M/L/H/L/M/I/M/I/M/L/H/L/M
With the central mild steel layer extending as a handle for the billet. You can see that 5 out of the 13 plates (actually about 50% of the material) is comprised of mild steel.
First weld - 13 layers (draw, cut to 4)
Second weld - 52 layers (draw)
At this point 2/3 of the bar was twisted in three sections, then cut
The remaining 1/3 was drawn, cut in half and matched to a carbon steel core
Third weld - edge at 105 layers
This was then forged to match the three twisted bars
Fourth weld - 261 layers
Forge to blade

As I have mentioned in other posts here, I have taken to making my knives using this method of a separate carbon steel core for the cutting edge with additional twisted rods forming the flexible and decorative back.

Sunday, May 25, 2008

'Espelund' Two Stage Process - Overview

(The following is converted from a posting to EARLY IRON)

Skip Williams wrote:

Espelund has had the idea for several years that his 'dust ore' was smelted in a two step process. It makes sense that the first step would be to sinter the ore in a furnace at an orange temperature and a low air rate until it sticks together. The second step would be to break up the sintered ore to 'normal' smelting sized particles and then smelt it in a bloomery furnace.

*********

Some maniac from Canada volunteered for a first test of that Espelund two stage process at the Heltborg event (in Denmark). And no, I have not crunched the numbers and formatted the images or written a report (yet).

As some of you know, Arne can be a bit difficult for us 'thick headed Poles' (sorry - in joke from the Seminar) to effectively communicate with. He is firmly entrenched in his viewpoint of analytical chemistry. Which of course explains much - but is often quite hard to convert to direct physical action. For the working iron maker, the answer to 'how much air' has to be answered in terms of at least litres per minute - not moles per smelt event. (In most cases, thats really more like 'pumps per minute' on an individual bellows. Arne often states that he finds our experimental process sloppy and lacking in critical measurements. He is most certainly correct - from the viewpoint of strict analytical science. Us working grunts however have such limited resources and are trapped by working in the dirty field, not a sterile laboratory.
Our efforts are ore to IRON - and the slag is just a waste product. Few of us even bother to weigh slag after the smelt, and there are extremely good practical reasons why NOT to bother. (more on that in a separate posting).

So - given what I could understand was the framework of the two step process, the sequence goes like this:
Step one is ore to iron rich slag mass
Step two is broken slag to bloom

If I got his point of evidence correct, he has examined a number (?) of Viking Age (?) iron smelting sites in Norway that show considerable volumes of materials (multiple smelts). At these locations he found remains of broken up slags, which looked like they were being intentionally prepared from larger slag blocks, and being collected for possible use as furnace charges.

I may have missed the point, but he did keep referring to 'broken slag' - not 'partially sintered ore'.

I saw two large potential problems with the process as he described it:
1) a duplication of effort and resources. Why run what was 'almost' a complete furnace operation (set up, cycle time, charcoal expended) just to produce a slag? Why not just run that operation (correctly) complete straight through to metal bloom?
2) breaking the slag mass from step one to prepare for step two is a HUGE amount of work. We all know how difficult it is to physically smash up slag compared to the effort required to prepare ore itself.

Anyway, without being able to provide (at this point) the exact details, the rough sequence of the experiment at Heltborg was like this:

The smelter used was a pretty standard 'short shaft' furnace:
Interior roughly 25 cm
working height about 30 - 35 cm above tuyere (55 total from base)
modified front plate (bellows tube tight to plate surface)
tuyere set about 10 cm above floor of smelter
provision for slag tapping, but not required

consumption rate of charcoal averaged about 10 minutes per kg (8 - 12 minute variable)
ore was added at roughly 2 kg per 1 kg of charcoal
total ore added was 14 kg
ore used was the 'Guldager' material (from Michael Nissen)

total production of slag was 11.2 kg
main slag mass was 7.5 kg
fragments recovered were 3.7 kg

The furnace was re-set, and Arne broke up the slag mass into typical sized pieces (roughly 'half walnut' or less) and sorted by eye.
The second firing:

working height about 50 cm above tuyere
tuyere angle at 22 down
(otherwise identical)

consumption rate of charcoal averaged about 7 minutes per kg (6 - 8 variable)
slag was added at roughly 1.5 kg per 1 kg of charcoal
total slag added was 7.75 kg

only a few small fragments of metal were recovered

So - right off the top, remember that this was the first working attempt at a brand new method. Two entirely new processes, plus some integration between these two - all three parts unknown.
On part A we got iron rich slag. How iron rich awaits tests by Arne of the samples he took.
On part B we did not achieve a viable iron bloom.

As Arne said ' Even a negative result is a valuable experiment '. I certainly would expect that to get this whole linked process working correctly, the development process will take as least as long as for two different smelt methods. (We all remember how long it took us to finally get any iron when we started!)

There are a number of what I feel are extreme challenges to get this process to work correctly. (This assuming that I got Arne's instructions on the chemistry correct.) What I recorded in my notes (please forgive me if I have this wrong!)

On the first step, the temperature range is extremely tight:
Require at least 1100 C to produce a working slag
But no more than 1200 C - which is "the threshold for CO production" (keep below to keep ore from reducing).
This is just way too tight a working range for the primitive equipment of an ancient smelter.

Anyway, that is the bare bones of the experiment. I'll let everyone know here when I get the experimental sequence formated and posted, plus the photographs of the process ready on the web site.

Darrell

Saturday, May 24, 2008

OVERVIEW - Iron Smelting at Heltborg


As regular readers here know, I was invited to attend this international gathering of experimenters working with various types of Northern European early iron smelters. Teams were present from England, the Netherlands, Sweden, Norway, several from Denmark, with myself from North America. There were a total of seven working teams, most of which fired at least twice over the six days. The stress was on historic furnaces and process, ranging from Early Iron Age through to Viking Age types. After a long day either smelting or in preparation, the evenings held presentations from participants or visiting archaeologists.

I have put together an overview of the Symposium laid out as a 'day by day' visual record of the main events on the main Wareham Forge Iron Smelting documentation:

http://www.warehamforge.ca/ironsmelting/HELTBORG/

As you might guess, I have been trying to plow through all the research from my trip. Not only iron smelting, but also visits to a number of major museum collections in Roskilde, Ribe and Copenhagen. On top of that, I am scrambling to get a number of projects sorted out and underway - to PAY for the trip! More chaos than normal around here...

Tuesday, May 13, 2008

Tents at Ribe Viking Centre

I have just posted a couple of my images taken at the Ribe Viking Centre over on the DARC blog, along with a short commentary on VA tent construction. This may be of some interest to those early period re-enactors reading this...

http://www.darkcompany.ca/blog/index.php

Monday, May 12, 2008

Viking Age Ship Building Tools

I'm trying to get myself back on to Ontario Time, and plow through all the data from my Denmark research trip. I hope to write up a number of shorter reports of various topic aspects of what I saw over the next several weeks. This pieces may prove pretty random, as they are likely going to follow other ongoing projects as I get into them...


I got the following information from Tom Nicolajsen, one of the lead boat builders at Viking Ship Museum in Roskilde:

1) You need two weights of axes - a heavier weight (2 kg) shapping axe and a lighter weight (1 kg) trimming axe.
2) On adzes in general - there are no tool marks resulting from their use on any of the Skuldelv ship finds
3) On the 'Bayeaux Axe' - there are no tool marks resulting from their use on any of the Skuldelv ship finds. Tom did note that this type 'makes work faster and easier'.
4) The small fine trimming adze from Mastermyr has proved 'not very useful'
5) STRONGLY recommends the use of a bow drill mounted spoon bit for drilling plank rivet holes (5 - 6 mm). This to avoid repetative stress (wrist) damage that results for the heavier 'cross' style mount (as suggested from Mastermyr) Save this heavy mount for the larger sized bits required for treenails.
6) Rivets set using two hammers (on the Mastermyr pattern), one at roughly 1.5 kg as the 'anvil' and a lighter 500 - 600 gm for the striking.
7) Shallow grove scraper is used not for decoration, but to make the line required to hold tarred rope caulking. This tool actually has the same grove pattern on either side of the central stop.

He further suggested that these tools should be provided:

- bow drill with spoon bit at about 5 - 6 mm

- caulking scraper
- roughling axe

- trimming axe (the one pictured was 'Tom's Favorite')
- heavy and light hammer ( already in smith's tool box ?)

- smoothing plane

He said the general method of work was to split out the planks, shape the rough contours as required to fit with the axes, then smooth the surfaces with the hand plane. They had two, the roughly 5 cm wide blade from Mastermyr looked the most used.

He did not talk much about saws, instead saying that all the shaping is done with axes.

Although he did not mention them, several wooden boat clamps are necessary. The ones used at Roskilde are closer to 60 - 80 cm long. They also are using (admittedly) modern threaded rods and thumb nuts - historically these clamp using wood wedges.

One of the objectives for my museum viewing was to gather information on Viking Age knives. I was surprised that at least for Denmark, AXES greatly outnumber knives (at least as represented in collections on view. I must have seen (and photographed) at least 50 Viking Age and Early Medieval axes. (The ones above from the National Museum in Copenhagen) There is a clear design difference between the various combat axes, felling axes and those intended for wood shaping in general.
 

February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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