[Nhcoll-l] Dealing with amber in mineral oil

[Neil Clark]

I presume you have read the article on amber conservation produced for EPISCON?

http://amsdottorato.cib.unibo.it/2259/

Neil


Dr Neil D. L. Clark
Curator of Palaeontology

The Hunterian
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________________________________
From: nhcoll-l-bounces at mailman.yale.edu [mailto:nhcoll-l-bounces at mailman.yale.edu] On Behalf Of Rhian Russell
Sent: 01 August 2012 21:40
To: nhcoll-l at mailman.yale.edu
Subject: [Nhcoll-l] Dealing with amber in mineral oil

Hey all,

I asked a while ago for advice on how to deal with amber that has been stored in mineral oil. I received many helpful responses which basically boiled down to:


-          Attempt to remove the mineral oil using a mild soap and water

-          Possibly grind or repolish the amber

-          Embed the amber in epoxy ( Paul Nascimbene recommended "a high-grade glass conservation epoxy called EpoTek 301-2". Other people mentioned reactions between the oil and epoxy so definitely be cautious with materials and techniques)

-          Cut down to study if desired.


We haven't gotten around to trying this yet but I figured I'd post the responses in case anyone else finds them useful. I have permission to repost from both Paul Nascimbene and Ryan McKellar.

Hi Rhian,

I hope I can be of some help.  We have occasionally encountered this problem here at AMNH, particularly with a few historical specimens, and with Lower Eocene Indian amber specimens that were recently sent to us in this condition.  Are the specimens in question amber pieces containing fossil arthropods?

I'm not sure that mineral oil can be completely removed from within the amber (depending on how deeply it has penetrated the material), but, in the case of amber with insect inclusions, the affected surface of the amber can be ground and repolished (removing the oil), as long as the insect lies adequately beneath the penetrated surface.  I might recommend first washing the amber gently with a mild soap and water (no solvents), especially if you have larger display specimens that are affected.  If the amber cannot be ground or repolished due to policy for the collection, then washing and thoroughly rinsing the piece may help prevent further damage, but the amber is still likely to deteriorate over time (see cons. doc attached).

Here at AMNH, we treat amber containing arthropods by embedding the amber under vacuum in a high-grade glass conservation epoxy called EpoTek 301-2 . I am attaching three documents FYI.

I am happy to answer further questions.

Best Regards, Paul

Hi Rhian,

I read the rest of the thread on 'cleaning amber' in the nhcoll listserv today.  Since the incident in the 90's with the original Type Sphecomyrma specimen, much has been learned about embedding amber specimens in epoxy, and we now use a higher grade epoxy that takes longer to cure, but has never produced an exothermic reaction in my experience (EpoTek 301-2).  I have used this glass conservation epoxy successfully on amber specimens that were coated with mineral oil (although I removed as much of the oil as possible beforehand by grinding and polishing the contaminated surfaces).  I suggest first trying this process on an expendable piece of amber that has either been immersed or coated with mineral oil.

Mineral oil will eventually fully degrade amber and likely ultimately compromise or ruin any inclusions the amber contains.  On the other hand, embedding amber in a high grade epoxy like EpoTek prevents oxidation and also significantly improves viewing of inclusions.


Regards, Paul

Hi Rhian,

Stacey Gibb forwarded part of the amber discussion that you have been having with Janet Waddington, concerning mineral oil storage. She figured I might be able to help out. When I went through the RTMP Grassy Lake collection, I didn't encounter any vials where the specimens were entirely submerged in fluid. There were a large number of samples in the type room in glass vials that had a thin film of what appeared to be glycerine clinging to them. (This and sugar-water are the most common modern solutions used for viewing inclusions, and will dry onto the specimens if they are not rinsed properly). To the best of my knowledge, glycerine does not react with plastic, but liquids like mineral oil and cedar wood oil haven't been used for quite some time (unless the specimens were loaned to some oddball researcher, or predate the bulk of the collection, the timing seems strange for mineral oil). The quick-and-dirty way of figuring out if you are dealing with glycerine vs. mineral oil is to take some of the fluid and mix it with water (glycerine should be soluble, given enough time, while mineral oil should be immiscible). If you do have mineral oil issues, there is very little that can be done without some risk to the amber. Probably the best long-term solution that comes to mind would be rinsing the amber pieces in a weak solvent to remove as much of the mineral oil as possible, drying them extremely well, and embedding them in a stable epoxy like Buehler's Epothin. The problem that Grimaldi and Nascimbene (1997) ran into was their epoxy reaching the temperature required to release the volatiles within the mineral oil that was stuck to their specimen. If small enough moulds are used for embedding (less than one inch, and with just enough epoxy to cover the amber piece) batch sizes should be small enough that heat should not be much of an issue. These authors  also mention that New Jersey amber is much more soluble than Canadian material, so Canadian amber is less likely to retain mineral oil within the amber itself. Ultimately, it will require at least one test specimen to see if any of this will work. If you would like help with the embedding, just let me know -- we do this sort of thing with Canadian amber at the U of A pretty regularly.
All the best,
-Ryan


Hi Rhian,
in the long run, I would strongly advocate embedding the pieces -- this and storing the specimens out of direct light is the only way to slow their eventual weathering. Many of the ROM specimens are difficult to study because the amber has significantly darkened and has developed large fractures that obscure the specimens. This is pretty scary, given that the collection only dates back to the late 30's. The same problem exists but is reduced in the Canadian National Collection of Insects and Arthropods amber collection, because most specimens were embedded early and only extend back to the early 60's. This said, most of the CNC material has been polished to expose the amber on at least two sides, so it will eventually share the same fate. I have attached the latest paper on these sorts of concerns.

The detergent idea is probably the gentler alternative to using a solvent, and would be better. We have had luck cleaning glycerine off of pieces using a very mild solution of "Sparkleen" (the residue-free laboratory glassware detergent) and then rinsing the material in distilled or deionized water. If the glycerine or mineral oil has largely evaporated, it might take quite a long soaking to loosen whatever is adhering to the specimens. If it is mineral oil, I am not sure that a detergent will be enough to get it off, but it is definitely worth a try.

Hope some of this helps.
-Ryan


The papers that were recommended are as follows:

Grimaldi, David and Paul Nascimbene.. "Appendix: Vacuum embedding and disintegration of the type of Sphecomyrma freyi." In "New and rediscovered primitive ants (Hymenoptera: Formicidae) in Cretaceous amber from New Jersey, and their phylogenetic relationships," by David Grimaldi, Donat Agosti, And James M. Carpenter, 41-43. American Museum Novitates 3208 (1997):1-43

Nascimbene and Silverstein. "The preparation of fragile Cretaceous ambers for conservation and study of organismal inclusions" in "Studies on fossils in amber, with particular reference to the Cretaceous of New Jersey". Ed. David Grimaldi, pp.93-102. 2000.

Bisulca, Christine, Paul Nascimbene, Lisa Elkin and David Grimaldi. " Variation in the Deterioration of Fossil Resins and Implications for the Conservation of Fossils in Amber". American Museum Novitates 3734 (2012): 1-19.



Rhian Russell
Conservation Technician
Royal Tyrrell Museum of Palaeontology,
Box 7500, Drumheller, Alberta T0J 0Y0
Phone: (403) 823 7707 Ext. 3306
E-mail: rhian.russell at gov.ab.ca<mailto:rhian.russell at gov.ab.ca>

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