Author Topic: Removing a glass coverslip: can it be done?  (Read 392 times)

dawncruth

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Removing a glass coverslip: can it be done?
« on: December 26, 2019, 03:26:03 pm »
Hi all,

A colleague donated their PhD thin sections for some research I'm conducting. Alas, these thin sections were made in the 80s where coverslips were the thing. Although super useful for petrographic work, they are effectively useless for SEM/Probe work. I also have current users (!) who have thin sections with glass slips who might want to do future SEM/Probe work.

Is it possible to remove the glass coverslip without damaging the rock slice too much?

If so, please share your wisdom. I imagine there are thousands of thin sections that could be made more useful if we could solve this problem!

Probeman

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Re: Removing a glass coverslip: can it be done?
« Reply #1 on: December 26, 2019, 04:13:33 pm »
I'm not an expert on this, but can you tell if the cover glass is mounted with petropoxy (epoxy), or balsam?

If balsam, you could just warm them gently and possibly slide it off.
The only stupid question is the one not asked!

Probeman

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Re: Removing a glass coverslip: can it be done?
« Reply #2 on: December 27, 2019, 11:31:36 am »
You might be able to tell if it's balsam by trying a tiny drop of acetone or turpentine on an edge. If the adhesive was epoxy then only (boiling) methylene chloride will work and that is very nasty stuff. The problem being if both glue joints are the same adhesive, how do you remove the cover slip and not destroy the thin section itself?

Ideally the rock is glued using epoxy, and the cover slip is attached using balsam.
The only stupid question is the one not asked!

dawncruth

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Re: Removing a glass coverslip: can it be done?
« Reply #3 on: December 27, 2019, 02:34:16 pm »
I've got to investigate the epoxy vs basalm question.

I've gotten a tip that placing the thin section in the freezer and gently prying off the slip works. 

sem-geologist

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Re: Removing a glass coverslip: can it be done?
« Reply #4 on: December 29, 2019, 08:58:53 am »
I want to give my 2 cents. I had seen quite many old refurbished thin sections, and I also had achieved that for one single thin section for my PhD (there was only thin section, no rock sample).

1. Tip for removing the cover glass (the easy step).
If the type of glue used for the cover glass is Canadian balsam it is very easy to get the glass dis-attached from the sample by freezing cycles (simple house freezer, I had done 8 cycles of freezing-unfreezing and the cover glass just completely got dis-attached.

2. refurbishing the thin section for modern EPMA (this is extremely difficult step, this requires very experienced grandmaster (we call them so) of thin section maker, luckily one of such grand-master is working in our institute).
The steps is quite clear:
2.1) very carefully removing the residual Canadian balsam from the fron side (where cover glass was removed) - the surface is very lightly polished
2.2) That polished side is glued with EPMA grade epoxy to the new base glass
2.3) The old base glass is little by little polished away to uncover the back surface

2.4) so if in last step glass had not split into pieces, or the sample was not too much polished away – You should have a new EPMA ready thin section . The difference from original is that it is mirrored – the back side of original thin section becomes new front side of the thin section.
« Last Edit: December 30, 2019, 05:27:53 pm by John Donovan »