Category Archives: science

Visualising lithic use wear traces – photo stacking

It is not always immediately apparent to non-specialists what we – use wear analysts – do and see and how we can be certain of our observations. This is partially due to the imagery many use wear analysts produce. In a recent paper A. van Gijn (2013) reflects on the current state of the field of lithic microwear or use-wear analysis and points out a number of aspects of our work in which improvements are possible or even necessary. These, in my opinion rightly, include an increase in sample sizes (e.g. by scanning tools with a stereomicroscope before moving on to higher magnifications); more incorporation of ethnographic data; a standardisation of practise and nomenclature; embedding the use wear traces in the cultural biographies of artefacts and providing better quality imagery.

The basal end of a Mesolithic scraper from Arconciel/La Souche, Switzerland (quartzit au grain fin/Ölquarzit). Left a normal photo. Right a composite photo of the same part of the artefact. Taken with a Keyence Digital Microscope.

The basal end of a Mesolithic scraper from Arconciel/La Souche, Switzerland (quartzit au grain fin/Ölquarzit). Left a normal photo. Right a composite photo of the same part of the artefact. Taken with a Keyence Digital Microscope.

The last point can be achieved by photo-stacking through the use of specialist software or microscopes, such as the digital microscope I use, which are able to make composite photos. The image above shows what photo stacking or composite photos allows you to do.

One major drawback of the microwear approach is the lack of convincing visual evidence. The pictures generally shown at meetings are fuzzy and lack depth of field. Usually only a small part of the photograph is sharp, namely the spot of polish we want to address. Although insiders may usually see and recognize what is being discussed, it is little wonder that the general audience has no idea what it has to look at and remains rather skeptical. There is much to gain from improving the visualization of the microwear traces. – A. L. van Gijn (2013 – p. 3)

Typically, it is difficult to make microscopic photos of larger parts of artefacts that are in focus. Photo stacking, however, allows exactly this: an increased depth of field with much larger parts of the artefact shown in focus. This way not only the traces, but also their contexts can be visualised. I find this technique does not work very well in all situations or for all raw-materials or for all traces. Nonetheless, it makes our work more effective and it will surely allow us to communicate our methodology and findings much better not only to fellow specialists, but also to non-use wear specialist archaeologists and the general public.

ResearchBlogging.org

Gijn, van A. (2013). Science and interpretation in microwear studies, Journal of Archaeological Science, DOI:

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Sharing the joy of scrapers

Fribourg near the SAEF

Fribourg near the SAEF

Today I met up with my project partner Laure in Fribourg, to discuss our progress and collect another sample of chipped stone artefacts for use wear analyses. We do not work in the same place and do not see each other every day. So, it is always stimulating and encouraging and fun to meet up and exchange ideas and plans as well as problems and results.

30 000 chipped stone artefacts (8000 - 7500 years old) on a table

30 000 chipped stone artefacts (8000 – 7500 years old) on a table

At the moment we are both working on the Late Mesolithic scrapers from Arconciel/La Souche, Switzerland. We are working towards a poster for the MesoLife conference this June and it is our aim to look at the relationship between production, use and raw material of the exceptionally many scrapers found at Arconciel/La Souche and how this develops towards the end of the Mesolithic. It was great to see that the method of our combined approaches will, as we hoped and planned, indeed bear fruit and comparing technology and typology with use will bring further insights into Late Mesolithic behaviour just North of the Alps.

Snapshot of the sample of Late Mesolithic scrapers (~6000-5500 BC) from Arconciel/La Souche I selected today

Snapshot of the sample of Late Mesolithic scrapers (~6000-5500 BC) from Arconciel/La Souche I selected today

 

Oh, and this is me playing with a fancy digital microscope. Thanks to the University of Fribourg for that!

Oh, and this is me playing with a fancy digital microscope. Thanks to the University of Fribourg for that!

Traversar III – a photographic record

Autumn has arrived in the Alps. The grass is losing its green lustre, leaves are slowly turning brown, farmers have moved their life-stock from alpine summer pastures down into the valleys and snow is expected later this week. Time to have a first cautious look back on this summer’s archaeological activities in the Swiss Alps.

I already wrote once about a small project we, a select team of expert alpine archaeologists (of course), started with the aim to study the archaeological remains at a number of the most important passes in the Grisons. This summer we were mostly active in the San Bernardinopass region. We also surveyed some areas in the Upper Engadin Valley which are to be subject to development in the near future. (For this we were officially commissioned by the Archaeological Unit of the Canton of Graubünden.)

We were lucky with the weather and were able to do all we set out to. We had some interesting results and although dating is difficult at this stage, we expect our finds to be both of medieval/early modern as well as prehistoric dates. While we are cleaning up the documentation, analysing the results and waiting for the C14 dates, I thought I posts some photos giving an impression of the fieldwork.

And if you are interested in the archaeology of the Alps, why not have a look at the alpine archaeology blog? Students of the Alpine Archaeology: tools and techniques e-learning course at the Universität Zürich will be blogging here this semester (DE).

During the fieldwork we discussed archaeology and bandes dessinée. We talked about the book Le soleil des morts, by comic artist A. Houot and archaeologists A. Gallay. (I believe it is not in print anymore.) I would be very interested in hearing about other good examples (in any language), so do get in touch!

The lab II: Is that a bit of dead sheepskin on your distal end?

After a short break, which I mainly spend writing the Hospental-Moos lithics report and flintknapping a bit, I am back at the microscope again. I now feel quite confident that I seem to have found my way around the machine and to have found, at least for now, my favourite settings. That is, the ones that seem best for my work. The photo shown here is a composite, The microscope takes a large number of photos, each with a different focus and combines them into a single picture with a large depth of field. This make it possible to produce the level of detail shown here.

The photo shows the distal, steeply retouched dorsal end of a scraper. That is lithic analyst speak for the scraper’s working edge, the bit that actually touches the material it is used to work. In this case that was dry sheepskin. And that is exactly what the white stuff atached to the stone is: sheepskin residue. At the Late Mesolithic site of Arconciel/La Souche (Switzerland) many very small scrapers were found and this scraper is pretty much an experimental replica of some of those scrapers.

Experimental hergestellter Kratzer aus Radiolarit. Kratzer wie dieses wurden in der Spätmesolithischen Fundstelle Arconciel/La Souche (Schweiz) gefunden.

Experimental hergestellter Kratzer aus Radiolarit. In der spätmesolithischen Fundstelle Arconciel/La Souche (Schweiz) wurden vielen solchen Kratzer gefunden. Bild gemacht mit einem Digitalmikroskop.
Experimental radiolarite scraper. At the Late Mesolithic site Arconciel/La Souche (Switzerland) many scrapers like this were found. Composite photo made with a digital microscope.

During its experimental life (More information and photos here), this radiolarite scraper was on of seven which we used hafted (in a wooden handle, using birchtar and sinue) or unhafted to scrape sheep- and goatskin. Now taken out of its haft and cleaned, it is part of the reference collection for my use wear project,