Tuesday, 12 March 2013

My own research

I study the chemical composition of samples of sheep wool found in archaeological deposits. These are mostly in the form of woven textiles, but there are occasional examples of un-spun raw wool. I am particularly interested in looking at textiles from the Middle Ages (approximately 600 to 1500 AD) in Europe.

3cm fragment of textile from Reykholt, Iceland
A tiny fragment of a textile from Reykholt, Iceland, dated somewhere between 1200 and 1400 AD. (c) Isabella von Holstein. I worked on samples from this site with Penelope Walton Rogers, by courtesy of Gudrun Sveinbjarnardottir [1].
This chemical analysis can show where the wool originally came from, because it is related to the local environment of the sheep that grew the wool. Because temperature, humidity, and rainfall change with distance across regions, so does the composition of wool from across the region. Composition can therefore indicate that an archaeological sample is made from wool which had been moved a long distance from a different environment. In order to do this work, I compare the regional patterns found in the composition of archaeological wool to those in archaeological sheep bone (same species, same time, different part of the body) and also to modern wool (same species, different time, same part of the body).

I compare the chemical information on origin to information derived from  the way the textiles are made. In the past, this changed over time and was different from place to place because of differences in technology (for example combing tools, spinning tools, loom type) or differences in tradition in different times and places. Now imagine at an archaeological site, you have found 50 textiles, of which two are very different: they are made using the same technology as the rest of the material at that site, but with different technical construction. They might both be imports. But they could both be local, and are rare either because of an archaeological accident (by chance, all other similar samples have decayed) or simply because they were only rarely made. How could you tell the difference? I hope that my chemical analysis method can help here, and distinguish between the movement of textiles themselves from movement of ideas about how to make and use textiles.

Tricky aspects

There are a number of difficulties with this work.  First of all, samples of wool in archaeological deposits are not intact. They are often stained brown and may well have been attacked by soil microorganisms or partially dissolved by soil water over their long period of burial. I have to be careful that changes to composition due to decay are not confused with differences in composition due to different origins.

3 archaeological textiles, all shades of brown
Textiles from the Museum of London

Secondly, environments, sheep and sheep farming have all changed between the past and now. Modern sheep farmers are likely to provide concentrate feeds during seasons when pasture plants don’t grow (winter in cold climates and summer in hot climates) and during lambing (because ewes can need better food in order to produce healthy lambs). These concentrates may include non-native species such as maize. Farmers may also use chemical fertilizer on fields. Changes in climate over time can also affect how sheep are managed, with farmers needing to respond to things like changes in the number of days of snow cover, types of plants in pasture fields, and periods of pasture growth. The breeds of sheep which exist today were mostly developed after the Middle Ages, so we don’t know how similar they were to the sheep that existed at the time [2]. So I need to be careful when selecting modern samples to reduce all of these factors as much as possible.

More about the chemical technique

The aspect of chemical composition that I am interested in is isotopic composition. In this section I’ll explain how this is different from other chemical measures of composition, and also how it relates to farming and origin.

All sheep wool from everywhere has very similar content of proteins, fats and pigment: this is called molecular composition. Each of these molecules is made of atoms, and so the overall proportions of atoms of the most common elements (carbon, hydrogen, oxygen, nitrogen and sulfur) in all wool everywhere is also very similar. This is called elemental composition. Therefore the molecular and elemental compositions of wool are not useful for identifying where wool comes from (though I do use them to work out whether decay during burial has significantly affected the fibres).

However some atoms have different versions of themselves which differ a little bit in weight but are still stable. For instance, carbon has 2 stable versions: carbon-12 (99% of all carbon atoms) and carbon-13 (1% of all carbon atoms). It also has 13 unstable versions, which are radioactive and decay, including carbon-14, which is used to date archaeological objects. The relative amounts of the stable versions of the elements, in this case carbon-12 to carbon-13, is called isotopic composition.

The isotopic composition of a sheep’s body depends on, firstly, the isotopic composition of the sheep’s diet, and secondly, the chemical reactions taking place in the sheep’s body as part of normal metabolism. The composition of sheep diet, which is largely pasture plants, depends on temperature, humidity, rainfall and vegetation type, and therefore varies with location. It can also be affected by farmers providing particular plants to sheep as fodder. We can therefore use the isotopic composition of wool to tell us about where it comes from and also something about how it was grown[3-4].

Stable isotopic analysis of the same elements (carbon, hydrogen, oxygen, nitrogen and sulfur ) is widely used in archaeology to study human diet in the past. However here, the focus is not so much on where humans lived as on what they were eating: how much meat? Any fish, and if so freshwater or marine? What sorts of plants? However, because human diets are much more complex than sheep diets, it’s more difficult to use this method to examine origin. Only oxygen isotopes are used in this way, together with the isotopes of other metals such as strontium and lead.

Why is this research interesting and important?

This research will help us to understand how textiles were made and moved in the past. Textiles today are not worth much because they are made by machine, but imagine if all of them had to be made by hand! A textile archaeologist calculated that it would take about 3 years for a single person to spin enough thread to make one Viking sail [5]. Once you add in the cost of the materials (the land and the livestock [6]) and the cost of weaving, it’s likely that the sail cost more than the boat’s hull. Therefore understanding archaeological textiles is much more than a hobby interest: these products required substantial investment, and could generate a substantial return: they made a significant economic difference. And because they were so laborious to produce, they also made a social difference. Being able to identify the ones which were moved long distances will not only tell us about how different places were connected in the past (often before the point where written records survive),  but also about how people organised themselves socially and economically to produce the local materials, which were themselves important goods.   

In addition, the same technique may be suitable to identify the origin of other objects from archaeological deposits which are also made out of the body parts of mammals: for example leather, parchment, fur, horn, bone or antler. The work on textiles is important because it is the first to try to work out whether this is possible. It would also be interesting to look at more textile fibres, including silk, flax and cotton.

1.              Sveinbjarnardóttir, G. (2012) Archaeological investigations at a high status farm in western Iceland. Reykjavík, IS: Þjóðminjasafn Íslands/Snorrastofa.
2.              Ryder, M.L. (1981) 'British medieval sheep and their wool types', in: D. Crossley (ed) Medieval Industry, 16-8. London, UK: Council for British Archaeology.
3.              Camin, F., Bontempo, L., Heinrich, K., et al. (2007) 'Multi-element (H, C, N, S) stable isotope characteristics of lamb meat from different European regions', Analytical and Bioanalytical Chemistry 389 (1), 309-20.
4.              Hedges, R.E.M., Thompson, J.M.A. and Hull, B.D. (2005) 'Stable isotope variation in wool as a means to establish Turkish carpet provenance', Rapid Communications in Mass Spectrometry 19 (22), 3187-91.
5.              Andersson, E. (1999) The common thread: textile production during the Late Iron Age-Viking Age. Lund, SE: University of Lund, Institute of Archaeology.
6.              Bender Jørgensen , L. (2012) 'The introduction of sails to Scandinavia: Raw materials, labour and land', in: R. Berge, M.E. Jasinski and K. Sognnes (eds), N-TAG TEN. Proceedings of the 10th Nordic TAG conference at Stiklestad, Norway 2009, 173-81. Oxford, UK: Archaeopress.

Sunday, 3 March 2013

The Fulford Tapestry

A couple of weeks ago I went to the York unveiling of the Fulford Tapestry. This is a commemoration of the Battle of Fulford in 1066 (Fulford is now a southern suburb of York), in the style of the Bayeux Tapestry. The new tapestry uses the same stitches as the original, in yarns dyed with natural dyes. (Neither of these objects are in fact tapestries at all, but embroideries.)

The new tapestry obviously recreates the visual language of the original:

You can see that these panels have in common: the figures of the woman and child and the burning house,  the strips of additional icons above and below the main story, some of the birds and beasts in these, and the sections of explanatory text. Elsewhere the distinctive interlaced trees of the original are recreated in the new Tapestry.

What was interesting to me however was where the new Tapestry departed from the original’s visual language, because this tells me about modern responses to this sort of story. In particular, I was struck by the abundance of blood on the new version, dripping from somebody’s head, colouring the river, and in pools under bodies, though this is not present in the original, even in the battle sections:

This must be something based our expectations from film and TV: someone’s not dead or injured unless there’s ketchup? Some of the dead have tongues sticking out. I can’t remember where this trope comes from, but I remember that this was code for dead when playing cops-and-robbers with my siblings when we were children. (The sound effect for this was “Bleugh”!)

Some more 20th/21st century features include a tower drawn with perspective, and images which feel to me inspired by photographs of modern re-enactments of the 11th century, in particular the walls of round shields and the bird banner:

The new Tapestry also includes marginal scenes derived from later medieval material such as the 14th century Luttrell Psalter, for example the reaping scene - compare to:

And there are scenes from Norse mythology: Tyr riding the wolf, Freya, and a famous valkyrie figurine:

Plus Godiva and Leofric (the 13th century legendary version) as a special bonus.

All in all: really interesting! And a considerable craft achievement. Hearty congratulations to Chas Jones and all the team. 

Sunday, 24 February 2013

Delayed gratification

I picked up my PhD thesis from the binder’s this week.

The weird thing is that this feels like it matters: it’s a relief. But I’m still not a doctor! Depositing the submitted, examined, corrected and bound text isn’t the end of the qualification process, it’s still the middle of it. I won't actually be Dr Holstein until I walk across the graduation stage in July and shake the Vice-Chancellor's hand, nine months after initial submission.

I'm working on a summary of this work in plain English, by the way. It'll be up here soon!

Monday, 18 February 2013

The lab landscape

We were going to have a visit from group of visiting potential students and their parents at our laboratories last week, as part of their tour of the department on an open day. I got asked to do the spiel for their visit. I was mighty stuck for what to say...I always find laboratories really unprepossessing to look at. Few people were wielding pipettes or peering into sample tubes, and the machines that go ping are often not at that part of their cycles.

I suppose it’s not surprising really that shows like CSI and their ilk jazz labs up with fancy lighting, coloured solutions in bulbous glassware, electronic gizmos and pumping music. The real labs I’ve been in have been a sort of ultra-clean shed-cum-kitchen, shared, cluttered and impersonal. And often with a lot of white noise in the background from various fridges, freezers, air-con units, centrifuges, ovens, fume hoods, etc.  I can’t say I find them very appealing spaces in themselves. The data you can generate in them give them an excitement of their own, but one which is very unlikely to be tangible to a stranger on a single visit.

The students never turned up, which may have had something to do with the snow falling at the time. Or maybe we got our wires crossed about the date. Still, there will be future visits. O readers: what would you like to see when visiting a lab?

Sunday, 10 February 2013

Where are the horned helmets?

I came across this set of photos of the upcoming TV series Vikings on a re-enactment mailing list recently. It got me thinking about how the popular image of Viking dress has changed over the years, and how little archaeological finds and research have contributed to it.

As an example, how about these from The Vikings, 1958:

as opposed to these from 2013:

I don’t think either of these productions were interested in what the clothes Vikings wore might actually have looked like. But they were having a lot of fun with what clothes the Vikings ought to have worn. This tells us more about what the Vikings mean to us than what they might have meant to themselves. So, the material culture the Vikings actually used  to communicate, and which we know about via archaeology, is not important. To modern audiences, the material culture they ought to have used includes:

1.   LOTS of leather. True in 1958 and 2013. Today this is all about badassness. Not sure about the 1950s - perhaps there were also hard-working/cool cowboy connotations?

2.   Lots of fur. Abundantly clear in 2013, but not so strongly signalled in 1958. I suspect this is visual shorthand for a lot of things: a simpler time (no PC objections), being close to nature (wearing grown things, not made things), and badassness (hunting and killing).

3.   Really huge crude stitching in 2013 but not 1958. Today, early medieval clothing is clearly supposed to be primitive. I suspect that in 1958, people knew that handmade didn't have to mean crude, but today too few people have any experience making clothing to feel that.

4.   Dark colours in all clothing, except for women when being rescued/wifely. True in 1958 and 2013, though in 2013 this is not the only role available (progress! Now we can be men  fighters too). I think we can blame Beau Brummel for starting this one, plus whoever designed the uniforms for the SS, biker gangs, and technological improvements in dyeing technology  which means that dark colours are no longer more expensive than light ones.

Some things have changed between the two incarnations of the Vikings. The 1958 short shorts and sheepskin boots have died in 2013 in favour of MOAR LEATHER. 2013 hair is different, reflecting hippy, punk and goth influences: there’s a distinct feeling of Vikings as counter-culture. Sleeves are longer in 2013, as are beards. Hmm.  

All is not entirely bleak, though, from the point of view of an archaeologist interested in dress/costume/textiles. There are definitely more accurate details in the 2013 production. There’s a hangerok, with beads and paired brooches (not oval brooches though). There’s relatively little wrong with this shirt. There are pleated patches on a kirtle here and all over an underkirtle here, though this one is crepe so it’s cheating, really. This shot includes 15-16th century costume detailing, the hooked-on sleeve. Wrong period, but still.

I don’t think I’ll be making the time to watch the new TV series. Maybe in 50 years time it’ll be interesting as a record of the twenty-teens...

(Edited Feb 2014 to fix broken image links)

Wednesday, 6 February 2013


So, bit of a gap since the last post. It turned out trying to start regular blogging during PhD writing-up year was not a good idea. But now that it's been submitted, viva'd, corrected and approved, things are moving forward again. Hooray!