This piece of material is curved, however I thought it was 'natural' originally, but the marks on the inner curvature appear to human-made and unlikely to be made by any natural process. It was found in the Tolka river in Griffiths Park, Drumcondra 53.369719, -6.261221
Can anyone shed any light?
Dear Thomas,
late medieval figurines made of pipe clay (terracotta) were often stabilised with textiles. And the structure of the fabric survieved firing. Please find attached a figure extracted from:
Tünde Kaszab-Olschewski & Volker Grimm, Trift Ton Textil? In: Lutz Grunwald, Den Töpfern auf der Spur. Orte der Keramikherstellung im Licht der neuesten Forschung RGZM-Tagungen 21 (Mainz 2015), 367-370.
On the left there is experimentally produced silk fabric soaked with slop after firing (positive). On the right there is postive textile structure found on a clay figurine from s'Hertogenbosh (Netherlands), dating to 1450-1480.
Best wishes,
Stefan
Thomas,
I have seen that exact pattern before and think the material is bone. However, currently I can not remember where I have seen it. Would it be possible for you to post photos of the other side and edge?
Thomas,
On second thought you might want to consider the possibility that it is asbestos tile.
Thomas,
I am now positive that it is a piece of corrugated asbestos cement roofing tile.
Asbestos tile (sheeting) is thinner and the dimensions are wrong for the curvature for the type of asbestos tile commonly used in Ireland in the last 50 years; however, that's a definite line to follow-up on and I'll compare the piece with actual examples of asbestos.
Thomas,
Corrugated cement asbestos shingles were being produced by 1900. There were many companies making the stuff and size varied. They also might have made Spanish/Mediterranean roofing tiles in asbestos impregnated cement, which probably were thicker. There were at least two different corrugated sheets: commercial and residential. The commercial type was thicker than the residential product. Also remember that the ridge cap might have been of the same material.
They also made non-asbestos cement shingles.
You can go to archive.org and search for asbestos shingles. There are many old company books that have this material in it. Unfortunately those that have photos instead of illustrations do not show a close up of the surface.
Attached is a stock photo from 3RF.com. While it does not give an age, this photo shows a similar, albeit not worn, pattern.
Hi James,
I think you have it! The 'shard' after kicking about in the river bed and becoming discoloured and buffed certainly started to look like something interesting! I think the 3RF.com photo settles it. Thank you for all your input.
The river in question at this section was messed around with a lot in the 1930s when much of Dublin in this area was built up.
This illustrates the need to be able to identify industrial era materials as much as the medieval (and pre-medieval in other countries). I had a hunch it wasn't natural but I could think how an inner curvature surface would have a textile imprint.
I'll check out archive.org and educate myself.
Thanks again.
Thomas
Thomas,
One way to check if it is cement asbestos is to take a sharp knife and carefully shave a flat spot on the lateral edge. Use a fiber mask so as to not breath any particles. You can then take a loupe and inspect the fresh surface. You should see some fibrous material in the matrix.
I have been analyzing prehistoric and historic artifacts for over 35 years. It sometimes takes me a while to remember where I've seen something before.
Best,
JAG
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