Paleonet: A sticky situation

James Davison jamesdavison at comcast.net
Tue Feb 23 04:50:40 GMT 2016


Does paraloid contain a drying agent?  In left uncapped the drying agent 
can evaporate and leave a slow-curing surface that remains sticky.

-- JD

On 2/22/2016 9:43 PM, Howard Gibbins wrote:
> Greetings,
>
> I recently ran across an odd situation, and was wondering if anybody 
> has, and whether they may have a solution?
>
> One of our volunteers recently prepared three Ceratopsian pedal 
> phalanges. They were easily cleaned and had minimal matrix. When they 
> were done the specimens were given a coat of Paraloid and put aside 
> ready for cataloguing and storage. This all happened at the very least 
> 4-5 weeks ago.
>
> When I went to pick up the three specimens the other day Paraloid had 
> not hardened, and in fact the surfaces of the specimens were extremely 
> sticky. The specimens easily adhered to my fingers, as well as to the 
> wooden tray they were laying on. It felt like they had been dipped in 
> a thin coat of honey.
>
> It was easily removed with acetone, after which I let the specimen air 
> dry and then gave it another coat of 1:10 Paraloid. Within a few hours 
> the surface was once again sticky (although not to the same 
> degree-thankfully). We have good air circulation in the lab, and the 
> temperature is constant at approximately 20 C. We don’t have anything 
> in the lab that the volunteer could have mistakenly put on in place of 
> Paraloid in the first instance, and I know it was Paraloid I put on, 
> as I’d been using it all day and everything else worked properly.
>
> So the question is does anyone know of anything that can prevent 
> Paraloid from drying, and even seemingly thicken it on the surface? I 
> assume it would have to be some chemical / or mineral that had leeched 
> into the bone during the fossilization process, or that the bone was 
> exposed to prior to collection, and was possibly released by 
> interaction with the acetone. Unfortunately I wasn’t the collector, so 
> I don’t know the environmental conditions at the site, but it came 
> from Dinosaur Provincial Park in Alberta.
>
> Thank you in advance,
>
> Howard Gibbins
> University of Alberta
> Laboratory for Vertebrate Palaeontology
> Edmonton, AB., Canada
> (780) 492-9366
>
>
>
>
> _______________________________________________
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> Paleonet at nhm.ac.uk
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