Experimental Archaeology - Warp Weights

At the start of the summer I began planning a rework of the Birka #6 brocade project I created for Dragon Mists’ baronial championship.  My goal is to do a single entry at Kingdom A&S next year, and wanted to incorporate all the feedback I received into a newer, better product.  Part of my judges’ feedback was to use a higher degree of period tools and process.  Prior to using a non-period loom to create my final project, I attempted brocade by using back-strapped tablet weaving technique and failed miserably (I couldn't get the consistent tension required for brocade), so I had a lot of questions about what sort of technique was utilized and started researching the topic from there.  

Birka is problematic because there are no existing loom extant examples, but there’s plenty of warp-weight evidence that speaks to warp-weighted looms being consistently in use.  Tabletweaving on warp weighted looms did occur (as evidenced by tabletwoven borders woven in conjunction with warp-weighted woven cloth), so I theorize that brocade work at Birka (or elsewhere/imported to Birka) could have likely been woven on the loom separately, using the same warp-weighted loom that would already be in the home and in use.  While there's fairly good evidence that much of the brocade was imported (at the very least, some of the materials), there are also examples that suggest the technique may have been learned/copied and produced there, as well (there are a variety of extant examples with a varying degree of expertise).

Rolling with the above theory, I decided in May/June that I was going to use warp-weighted technique in my next reproduction of the #6 brocade.  When I mentioned wanting to make my own clay warp weights to Meistara Reginleif (I’m her student) she suggested I fully research the process and that we could do it sometime over the summer.  Phew… I had no idea what I’d be getting into at that point!  Birka’s warp weights vary quite a bit, but there are a few examples of weights weighing 150-200 g and having diameters of 7-8 cm – so I decided I’d aim for those measurements. Reginleif has natural clay available on her family’s land and we had been discussing an experimental archeology weekend… so we decided that the beginning of August would be the best time to attempt this project.

First – I want to assure you that I knew absolutely zero about ceramics, pottery etc. before doing any of this research.  I still feel like I’m just scratching the surface.  I think that’s one thing I really want to highlight that can be intimidating from viewing things in the Arts & Sciences world – it is easy to assume that people have more knowledge than they do based on what they post, but I highly encourage anyone that is interested in a thing or even interested in just getting the final product to look into how it was done and to try to follow the period steps to do it.  It is very rewarding, even if it blows up – which I was almost 80% certain would happen with this project.  If you are at all interested in how I followed this side-rabbit hole as part of my weaving project, feel free to reach out – I’m always happy to help (and go a little nuts at you, probably).

I read a lot of websites and articles (many of which I’ve linked below) and concluded that they likely used a pit-fire to make earthenware (the warp weights at Birka are earthenware).  Stoneware (what we use for modern ceramics) wasn’t available in that area during that period.  Earthenware is porous and isn't used in daily life in modern times because bacteria can get trapped in the pores of the pottery even with thorough cleaning, so anything we made during our experimentation wouldn’t be appropriate for food/beverage use (warp weights fit the bill perfectly for this type of project). Clay changes to Earthenware at 800-1000 °F so our clay goods needed to reach those temperatures and remain there through out the process.

Using a variety of sources, we put together a basic step by step process of how we were going to attempt this and, of course, everything starts with the clay.  Reginleif did some preliminary tests from our initial discussion of first steps and determined that we probably didn’t have enough days set aside to do everything we needed to do, so she went ahead and harvested the clay and performed the first part of the process (getting the clay dug out and processed into a workable state).  I then shaped the clay into the warp weights.  Reginleif also acquired some commercial clay because we were uncertain if we would be able to get the desired result from the naturally-sourced clay.  I did some coil tests with the natural clay and determined that combining the two types of clay would likely yield the best result (I ended up forming some weights with just natural clay and one with just commercial clay for science)!  We then waited for them to dry.  Our instructions indicated that an oven is modernly used to dry pottery at low heat (around 200 °F), so I used one of the cooking fires for this purpose and hung the weights off to the side to use the residual heat to dry them more rapidly.  After that, we placed them in a pit-fire and fired them for 4 hours before smothering the fire with dirt.  Smothering the fire allowed them to bake longer while the heat died off under the dirt (it also cut off the oxygen which had the added cosmetic effect of turning everything a nice shade of black… I read about the technique in an article and wanted to try it for fun!).  Below are all of the above steps (and associated photos) that describe the process in much greater detail:

Step 1 – Find a good site for excavating natural clay (this is part of a dried up pond on Reginleif’s family property).  Dig up a good quantity for project use (we ended up having a bunch left over)!

Step 2 - Separate any large contaminants (like straw, rocks) to ready the clay for processing.

Step 3 - Add equal parts water to the clay and dissolve as much as possible into a slip (mix until smooth).  An article I pulled information from said the clay should have a smooth, creamy consistency - kind of like gravy.

Step 4 - Coax the liquefied clay through a fine mesh screen to further separate rocks/sand/other large particles from the clay (do this over a second bucket).  Don't use your bare fingers, it'll make them raw and destroy your nails!  One site used a spatula to push the clay through the screen, but I believe Reginleif just used gloves.

Step 5 - Wait a a couple of days for the water to separate from the clay (the clay will sink to the bottom) and pour out some of the excess water.  Then allow some of the rest to evaporate until it is a workable (very wet) consistency.  The timing of the process depends a great deal on how humid it is where you are at (it was very humid the week we were doing this, so drying the clay took longer).

Step 6 - Lay out the clay on canvas (or another cloth surface, we used a drop cloth) to dry further until the clay is a pliable consistency (like clay you'd buy from the store).  You should be able to mold it in your hands without it breaking (too dry) and without liquid being left on your hands (too moist).  

We did a few tests during this process to determine the level of sand content still in the clay (this can cause pottery to break apart during firing).  The natural clay stood up pretty well to the coil test (roll the clay to where its the diameter of a pencil and then try to wrap it around your finger to see if there's breakage - if there is, the sand content is too high).  There was minimal breakage (but still some), so I decided to incorporate a small percentage of commercial clay into my weights.

Step 7 - I formed the warp weights from the natural clay - for most I used a mixture of natural and commercial clay (mostly natural with a little bit of commercial to give it a less sandy texture).  I did do a few test weights with 100% natural clay and one with 100% commercial clay as my "control" weight - I mainly wanted to see what combination of clay turned out the best post firing!  I added one layer of slip (clay/water mix) to the outside of the weights to give them a smoother texture since I'll be wrapping them with yarn and don't want sharp/cutting edges.

Step 8 - I took the advice I read in an article apply low heat to speed up the clay drying process.  I did this by commandeering Reginleif's and Khalja's iron grills and air baked the weights next to a low heat fire.  I flipped the donuts on occasion, but they never got too hot for me to touch them with my bare hands (just pleasantly warm).  I do think placing the weights near the fire for about 8 hours assisted in speeding up the drying process.  If left to air dry, I think this step would have taken several days.  (We also made some cups for fun just to see if they'd stay intact through the entire process).

Step 9 - I dug a fire pit!  There is a lot of conflicting information (or vague information) on how deep to dig the fire pit and what fuel to put in it.  I ended up using a compilation of suggestions from a variety of different resources.  The pit was dug roughly a foot deep, we then used a base layer of spruce wood chips, and placed the pottery/warp weights on top of them.  We used bricks in between the pottery to provide an air insulation barrier (one article suggested that) and to stop any larger pieces of wood from collapsing into our items during firing and breaking them accidentally.

Step 10 - We added wood chips into the cups and on top of the weights, and then added a layer of cow dung (for insulation and slow burning - many articles suggested an animal dung layer to get higher heat).  We also put some charcoal on top of that and sprinkled a little bit of horse dung because we had that available for our use, too.  Once the charcoal got burning, we felt that it would provide an evenly high temperature over our all our pottery locations.

Step 11 - We then built our fire - Olin suggested that we build several fires in the pit so we'd have fires going everywhere (to facilitate even burning) and that we could just add fuel from there.  We used kindling and cedar to start the fire and alder logs to maintain it.  Special thanks to Tiernan and his boys for all the fire-related help this weekend.

Step 12 - Many articles didn't give any sort of timing as to how long to continuously fuel the fire.  One article said they did it for four hours, so we ended up going with that.  We continuously added alder logs/sticks to the fire for four hours and it got very very hot.  We don't know how hot because we left the temperature gun at the house, but we figured we'd know if it got hot enough by examining our end result so, unfortunately, we don't have any temperature readings to share.

You can see in this picture that the charcoal is doing its job providing that consistent heat layer.

Step 13 - After 4 hours we let the fire burn down a little and smothered it with dirt.  This allowed the residual heat to stay in the pit and continue baking the pottery.  The smothering also cut off the oxygen to the fire which one article said would give us pretty black pottery as the result and I wanted to see if that worked for aesthetic reasons!  We left everything buried overnight (roughly 13-14 hours in the ground).

Step 14 - Digging everything up!  We carefully excavated our fire pit the following morning and hoped for the best.  As we started to uncover things, we got really really excited.  We pulled up the cups first (mainly because we thought they stood the least chance) and were very happy to see that they all made it, turned black like we anticipated, and passed the *tink* test.  Apparently if you flick the pottery with your finger and it makes a *tink* sound, it means you successfully made earthenware and reached the 800-1000 °F threshold.

All of my warp weights but one made it through the firing process, and four were already cracked from baking going into the pit.  All the clay weight examples (natural clay, commercial clay, and mixed clay) successfully made it through firing (and look fairly identical after firing).  I'm really pleased with our results.  

End results were pretty close to the extant examples (check out the deep black color after I washed them at my house).  Can't wait to test them out!  (Photos are my result and the extant example):

All and all it was a beautiful, educational weekend with friends.  I'm pretty exhausted, but can't wait for the next phase of this project!

Below is a list of articles and resources I used - I'll likely do a paper on this topic at a later date.

Web Technique References:

1.    Bartel B.  How to Rework Clay & Fire without a Kiln.  Goshen College. Indiana.  2016.  (https://www.goshen.edu/art/DeptPgs/rework.html)

2.    Beatson P. Experiments with Early Medieval Pottery. NVG Mikligard. 1997.

(http://www.miklagard.nvg.org.au/articles/pottery.htm)

Further Reading/Research Basis:

(Archaeological)

1.     Andersson Strand EB. Experimental Textile Archaeology. In Andersson Strand E, Gleba M, Mannering U, Munkholt C, Ringgaard M, editors, NESAT X, 10th North European symposium for Archaeological Textiles, Copenhagen 2008. Vol. 5. Oxford: Ox Bow Press. 2010. p. 1-3.

2.     Martensson L, Nosch ML, Andersson Strand EB. Shape of Things: Understanding a Loom Weight.  Oxford Journal of Archaeology 28 (4). 2009.Andersson Strand EB. Tools for Textile Production – from Birka and Hedeby. Stockholm, 2003.

3.     Stirling L. Milek K. Woven cultures : New insights into Pictish and Viking culture contact using the implements of textile production. Medieval Archaeology 59 (1). 2015.

4.     Thorin I. Weighing the Evidence - Determining and Contrasting the Characteristics and Functionality of Loom Weights and Spindle Whorls from the Garrison at Birka (Thesis). Dept. of Archaeology – Stockholm University. 2012.

5.     Klessig BK. Textile Production from Viking Age Graves in Gotland, Sweden (Thesis). Humbolt State University. 2015.

6.     Petty C. Warp Weighted Looms: Then and Now, Anglo-Saxon and Viking Archaeological Evidence and Modern Practitioners (Thesis). University of Manchester. 2014.

7.     Sjobeck A. The Important Craft: Textile Tools and Production in kv. Trädgårdsmästaren in Sigtuna. Lund University. 2014.

8.     Becker CJ, Jørgensen LB, Hvass S, Nielsen LC, Skov T and Stoumann I. Viking age settlements in western and central Jutland: recent excavations. Acta Archaeologica 50. 1979.

9.     Ramskou T. Viking age cremation graves in Denmark: a survey. Acta Archaeologica 21. 1950.

10.  Roesdahl E. Viking age Denmark. British Museum Publications: London. 1982.

11.  Stenholm L. Hushållskärl av aldre svartgods. In: A.W. Mårtensson (Ed.) Uppgrävt förflutet för PKbanken i Lund (Archaeologica Lundensia VII). Kulturhistoriska Museet: Lund. 1976.

12.  Thompson MW. Novgorod the Great: excavations at the medieval city directed by Artsikhovsky AV, Kolchin BA. Evelyn, Adams and MacKay. London. 1967.

13.  Vince A. Aspects of Saxo-Norman London II: Finds and environmental evidence. London and Middlesex Archaeological Society: London. 1991.

(Further Technique)

1.     Nigrosh LI. Low fire: Other ways to work in clay. Davis Publications: Worcester (Massachusetts). 1980.

2.     Primmer L. Pottery made simple. W.H. Allen: London. 1974.

3.      Reigger H. Primitive pottery. Van Nostrand Reinhold Co.: New York. 1974.