[Nhcoll-l] Restoring a damaged transparent specimen

[Fabian Neisskenwirth]

Dear Claire,


I've been working a lot with Spalteholz specimens lately. I'm a bit 
surprised that it was transferred it to glycerol, since none of the 
chemicals (methyl salicylate nor benzyl benzoate) are really miscible 
with than medium (glycerol). Bedsides that as in ethanol, there is no 
real absolute glycerol solution. It will always absorb some water. And 
there is the whole issue. The Spalteholz chemicals are absolutely water 
repellent. In the official methodology you actually go from "absolute" 
ethanol to benzene in two different baths, to extract all of the water 
content from the specimen. From there you go to the methyl salicylate. 
The whole method is based on optical properties of the medium. So yes, 
in theory you should be able to make the whole clearing possible again. 
This depends on the state of preservation of the specimen.

I would be careful with the assumption that your deposits are lipids. It 
is more likely that through the wrong transfer something has interfered 
with the whole mixture between glycerol and the methyl salicylate. It 
could have formed some kind of emulsion. A picture could help to clarify.


I recommend you to read Spalteholz's publication, if there is some kind 
of translation (maybe some translation tool might help). Its really 
interesting and explains very clearly how the whole methodology works. 
This could answer your second question.


I hope this help a bit.


All the best!




Am 05.11.25 um 10:18 schrieb Claire Smith:
> Hi everyone,
>
>  With apologies for cross-posting, I'm looking for some advice about 
> working with a damaged specimen.
>
> It's a newborn monkey that was originally an alizarin transparency, 
> prepared by the Spalteholz technique 
> (https://doi.org/10.1016/s0940-9602(01)80020-0 
> <https://doi.org/10.1016/s0940-9602(01)80020-0>), with our catalogue 
> listing the preservative as "Methyl salicylate 5: benzyl benzoate 4".
>
> In 2008 it was apparently in poor condition with crystal deposition, 
> and it was transferred into 100% glycerol.
>
> Currently, a lipid layer has formed at the top of the fluid, which is 
> also cloudy - presumably also with suspended lipids.
> The tissue is no longer transparent.
>
> My questions are:
>
> Is it possible to make the tissues transparent again? (If so, how?!)
> Is it best to keep the specimen in glycerol, but dilute it to a more 
> appropriate concentration?
>
>
> Many thanks,
>
> Claire
>
> *******
>
> *Survey: Fluid Preservation Methods in Biological Collections*
>
> _https://app.onlinesurveys.jisc.ac.uk/s/reading/fluid-preservation-methods-in-biological-collections_
>
> *******
>
> *Claire Smith *(she/her), AFHEA
>
> *Graduate Teaching Assistant: *Tuesdays and Wednesdays
>
> *PhD Researcher: *Mondays, Thursdays, and Fridays
>
> *
> *
>
> *Cole Museum of Zoology*
>
> University of Reading
>
>
> _claire.smith at reading.ac.uk_
>
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