[Nhcoll-l] [EXT] Sea turtle restoration

Tue Dec 6 09:50:33 EST 2022

Close, but not quite. The scutes are keratin not chitin. Chitin is chemically similar, but it is the exoskeletons of insects. The scales, feathers, fur, horn and hoof of mammals, birds, and reptiles are keratin. 
Oil will indeed colour saturate the keratin, and in some ways is good for it, but also attracts dirt over time and can cause things to darken and blacken over the long term (decades), with a hardened layer of adhered dirt. Keratin is also easily scratched and the attracted dirt can increase this risk. Depending on the long view for the specimen, it may or may not be preferable to use this. The Paraloid B72 will also colour saturate the scutes to make them look brighter, but it will dry to a finish that does not attract dirt, and be somewhat protective against scratching.
Keratin can be damaged by heat, so I would probably avoid the hot glue, although the exposure time is relatively short.
These points are relatively minor, but this is the approach us Conservators take.
Valerie Tomlinson

-----Original Message-----
From: Callomon,Paul <prc44 at drexel.edu> 
Sent: Tuesday, December 6, 2022 9:38 AM
To: Valerie Tomlinson <VTomlinson at nature.ca>; Art Van Arsdale <vanarsdale2640 at hotmail.com>; nhcoll-l at mailman.yale.edu
Subject: RE: [Nhcoll-l] [EXT] Sea turtle restoration

Polyurethane varnish will yellow and fall off fairly quickly, I think, as the scutes are chitin. If you are displaying the shell, it might be better to dress the scutes with something like glycerol or mineral oil once you have glued them back. Wipe or brush it on, wait a few days, then polish the surface. That will also keep the scutes flexible, prevent cracking and show their color well. You'll have to renew it every few years, but that's easy.

Elmer's glue (PVA) is not a good idea; it gives off acetic acid when fresh, and won't grip chitin for long. Though one might hesitate to recommend it, hot glue (from a glue gun) sticks well, has considerable bridging and filling qualities and is less chemically disruptive because its tackiness is the result of heat, not solvents.

Paul Callomon
Collection Manager, Malacology and General Invertebrates

Academy of Natural Sciences of Drexel University
1900 Benjamin Franklin Parkway, Philadelphia PA 19103-1195, USA prc44 at drexel.edu Tel 215-405-5096 - Fax 215-299-1170

-----Original Message-----
From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> On Behalf Of Valerie Tomlinson
Sent: Tuesday, December 6, 2022 9:25 AM
To: Art Van Arsdale <vanarsdale2640 at hotmail.com>; nhcoll-l at mailman.yale.edu
Subject: Re: [Nhcoll-l] [EXT] Sea turtle restoration

External.

Hi Art,
First question is: are there any future scientific analyses that you don't want your treatment to interfere with?
Second question: what is the intended use of the specimen in question?
Once you've answered that question, then you can look at what treatments are possible within those bounds.
It might be a case of packing things carefully so that the pieces don't get disassociated. If there is no intent to display, then it doesn't have to look pretty. It just has to be use-able for research, and/or stable in storage until it is needed.
If it does need to look like an assembled and complete shell, and you don't have to worry about interference with analyses, then I would probably start my adhesive search with Paraloid B72. You could also use that as your topcoat if you wanted. It's more reversible and less prone to yellowing than polyurethane.

Valerie Tomlinson

-----Original Message-----
From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> On Behalf Of Art Van Arsdale
Sent: Monday, December 5, 2022 8:16 PM
To: nhcoll-l at mailman.yale.edu
Subject: [EXT][Nhcoll-l] Sea turtle restoration

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Hello everyone. I work at a nature center in South Florida. We have an old green turtle shell that has fallen into disrepair. The scutes are coming off. I believe I can remove them all one at a time but I am not sure what adhesive to use to reattach. Web searches suggest Superglue or Elmers glue but I'm not sure that would be a permanent solution. Also, I am planning to topcoat with a water based polyurethane.
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