[Histonet] Epon Resin Embedding Question

[Duraine, Lita R]

Hi Brian,

I regularly use epon for TEM work.  Even though the instructions are good for some climates , epon is particular.
Here in Houston, I let my blocks cure for 5 to 7 days depending on how humid or rainy it is.  When I press a fingernail into the block , if it leaves a mark I know it needs a day or two more.  I generally cure at 62 degrees Celsius.

Dryer climates you can get away with shorter cure times.  Just do the fingernail test before starting to section.

If your blocks were in the oven for that many days already, then one of the components of the epon resin was no good or contaminated.  If that is so you may salvage your specimen by going backwards in a few steps in propylene oxide, or whatever other dehydration solvent you used before trying to cure in epon.  After you get your sample loose then continue forward with new epon, ddsa, nma, and the harder dmp-30.

Regards,

Lita Duraine
Baylor College of Medicine
NRI TEM Core
1250 Moursund St.
Houston, Tx 77030




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-------- Original message --------
From: Paula Sicurello via Histonet <histonet at lists.utsouthwestern.edu>
Date: 9/28/22 10:29 PM (GMT-06:00)
To: "Cooper, Brian" <bcooper at chla.usc.edu>, "Cooper, Brian via Histonet" <histonet at lists.utsouthwestern.edu>
Cc: "Navarro, Alexander" <anavarro at chla.usc.edu>
Subject: Re: [Histonet] Epon Resin Embedding Question

Hi Brian,Unfortunately, no.  The most you can do is to put it back in the oven and let it bake forva very long time.
You won't be able to section it.  It will gum up the knife edge.  If they are using a diamond knife they need to clean it right away.
To add insult to injury, the poorly polymerized blocks are a safety hazard.   Epoxy resins are all toxic, carcinogenic, mutagenic, a reproductive hazard, or all of the above combined.  It’s only when the resin is fully polymerized that it becomes an inert plastic.
Perhaps someone else out in Histoland (Tim Morkin, are you out there?) has had luck dealing with blocks like those.
Sincerely,

Paula Sicurello

  On Wed, Sep 28, 2022 at 12:27 PM, Cooper, Brian via Histonet<histonet at lists.utsouthwestern.edu> wrote:   Good afternoon Histonet,

Asking this question for a friend:  Is there a way to correct an improperly prepared Epon resin embedded block?  Following embedding, the block is soft and "tacky" to the touch.  This block is proving VERY difficult to section.  Any assistance from those of you doing EM in your labs would be greatly appreciated.

Thanks,

Brian D. Cooper, HT (ASCP)CMQIHCCM| Histology Supervisor
Department of Pathology and Laboratory Medicine
Children's Hospital Los Angeles
4650 Sunset Blvd MS#43- Los Angeles, CA 90027
Ph: 323.361.3357
bcooper at chla.usc.edu<mailto:bcooper at chla.usc.edu>

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