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Guy Osborn

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Reply with quote  #1 
Like many others I am saddened on many of my visits to Folkestone, finding beautiful gastropods with ornate shells, knowing that ONLY the shell is preserved, and that the  shell is only filled with clay. Is there any way (eg PVA, superglue, Sally Hansen Hard as Nails etc) of strengthening the shell, glueing clay and shell as the clay shrinks and cracks, so that one is left with something - perhaps not of museum value, but as a record and a thing of beauty?
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prep01

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Reply with quote  #2 
Hello guy, I haven't had anything from Folkestone, but I have discussed your situation with a preparator who lives down there. We agree that after desalination, the specimen  with the clay filling should be dried slowly and then soaked in 5% Paraloid weight / volume in acetone, allowing it to penetrate the shell and the clay. Depending on the size of the gastropod I would suggest soaking for a few hours for small ones and using a sliding scale up to a day or so for large ones. Remember that acetone will dissolve plastics so use a glass container with a close fitting lid, making sure that the specimen is well covered with the consilidant mixture.
Hope this helps

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Colin Huller
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Guy Osborn

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Reply with quote  #3 
Hi Colin,
Thank you - I am really looking forward to my next visit now! Two quick questions:
1. Paraloid B72?
2. What about shells with very ornate varices (if that is the correct term for outgrowths and spines)? I do not think they would survive away from the clay. and had visualised keeping the clay matrix to help stabilise and conserve. I picked up an incomplete yesterday, just to identify and throw away, which is what led me to thinking and my original post. I attach a photo to try to give you an idea of what I mean. 20180214_112403[1].jpg
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prep01

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Reply with quote  #4 
Hi Guy,
1) Yes!
2) Desalination is vital - soak in a bucket of water for a few days ( I would trim the block first and change the water a couple of times). I am in the process of developing a test kit to check the waste water for salt - if you are interested in a trial kit please contact me - details in profile.
3)Keep the clay inside the specimen.

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Colin Huller
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ThomasM

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Reply with quote  #5 
No no no no no, 100% do NOT soak this, it will completely destroy it. I have collected and prepared many of these Apporhaid gastropods from Folkestone successfully and this is the method I use.

1) After collection, if the clay is wet, first fill any major cracks with superglue then put it in a plastic bag (doesn't need to be completely sealed) and leave it to dry over a period of a few weeks. This will allow it to dry without the clay cracking and the shell lifting off.

2) Prepare the shell with a round-ended scalpel and then use a small paintbrush dipped in water to gently clean any remaining clay off of the shell.

3) Coat the entire shell in Paraloid b72, use quite a strong solution, maybe 20-30%. I know some people say use only 5-10% to reduce shine but to be honest that's so weak that it will not stop the shell flaking and deforming, you need to harden it completely. For fragile areas you can apply thin superglue to the surface of the shell. There is probably no need to coat the matrix in anything if all the cracks have been filled but if it is very flaky in the past I have first coated it in paraloid and then scraped off the surface to restore the natural look.

As I stated previously you absolutely cannot soak these blocks. Solid pyritic and phosphatic fossils from Folkestone should be soaked to remove the salt, but the most you can do with these clay blocks is preserve them. The effect of salt decay is generally minimal on gault blocks, it's not like chalk fossils where echinoids can literally explode off the surface of the chalk in 10 years if not desalinated properly. The majority of gastropods in museum collections from the Victorian era are still fine if they haven't succumbed to pyrite decay by then, and they were certainly not soaked.

That's a nice specimen of Pseudanchura carinata by the way, shame about the area of missing shell

As an example here's a specimen from Bed VII prepared in this way recently

26047197_353745435035676_642742810975635447_n.jpg 


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Thomas
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