A first attempt at soil-block radiography
A block of soil with suspected hobnail shoes within is confirmed using x-rays. Whilst the leather has long decayed away, the nails have remained in place. In this example it is difficult to determine whether the heel of the shoe is to the left or right, but the outline is evident.
Following on from my tour of the Canterbury Archaeological Trust, I have liaised with Adelina Teoaca to image some suspected Roman hobnail shoes. Adelina is a very knowledgeable archaeologist with an eye for detail. The Trust have a Faxitron x-ray machine that uses chemical film to provide imaging, something that is considered very old fashioned in the clinical environment but financially cheaper than purchasing a computed or direct-digital detector. As soon as Adelina mentioned she would like to x-ray her hobnail shoe soil-blocks I offered my services - I am very interested in learning to image specimens other than human remains.
One of the specimens, out of its protective cellophane wrap.
We conducted imaging on a selection of suspected shoes, taking photos as we went along. The first shoe was out of its protective wrap and was imaged 'as is' to test our exposure values. I went for a healthy 70 kV and 5.6 mAs (at 100cm). The cremation urns required far greater exposure values, but these soil blocks were smaller and thinner. My guess was a good one - nice images first time - so we proceeded to image each 'shoe' in turn. Apart from the specimen shown in the photo above, all the others were placed on planks of wood and heavily wrapped. Despite my worries, the wood did not impede the quality of the resultant x-rays. Of all the specimens that Adelina brought, only one did not have a shoe within it.
The x-ray of the open (and fragmented) shoe. The soil was dry, which helped to reduce the overall density of the specimen and improve image quality. The hobnails were clearly demonstrated, although their original position have been disrupted. The 'toe' of the shoe is to the left of the image.
A key advantage of the digital radiography equipment at Canterbury Christ Church University is the ability to digitally manipulate the imaging to visualise different structures. For example, the brightness and contrast of the images can be adjusted to show the hobnails, making lower density structures less visible. And, as mentioned in previous posts, the digital radiography system allows you to take multiple images without spending money on film. The only burden is that of data storage.
On of the shoes wrapped and placed upon a wooden board.
We haven't analysed the x-ray yet, but it seems that the shoes were compressed within the grave, so any decorative effect the hobnails may have shown are now not visible by their distribution. The size, shape and position of the hobnails are still interesting, especially as they 'point' inwards, giving an indication of their original orientation. The majority of the x-rays were taken from above (what I would call anterior-posterior or dorsi-plantar for a foot x-ray). Only one specimen was imaged from multiple angles because we couldn't work out which way way 'up'. In theory we could have taken two x-rays from 90 degree angles to demonstrate the distribution of the hobnail in all three planes. In truth though, the shoes have all been compressed flat, meaning that multiple radiographic views have little value.
Another hobnail shoe. The toe of the shoe is to the right, the heel is to the left. The direction of the nails can be discerned by their point. Further analysis is required to ascertain their potential construction.
Images: All images were taken by the author.
Reproduced with permission from Canterbury Archaeological Trust and Canterbury Christ Church University.