[Histonet] Cracking paraffin blocks

[Wheelock, Timothy R.]

Hi Everyone:

Recently, I purchased the Medite Valida Embedding Center, which I demoed previously without a problem, if I recall right.
I am having problems now with blocks developing cracks on the cold plate.
The cracks run either through the wax right next to the specimen, or more frequently, right through the tissue itself.
I use Surgipath Embedding Media (EM-400).
The surface of the Valida's cold plate is -14C.

The company has not seen this happening before, but they are looking into this further.
Also, I had the same problem when I demoed the Thermo-Fisher HistoStar.
I do not think that this is a problem inherent with any particular machine.
Has anyone encountered this problem before?
If so, how did you resolve it?

Is it possible that the -14C cold plate is too cold? Should I warm it up a bit?
The surface of the Valida cold plate is, I believe, made out of smooth stainless steel.
My old (24 years) Shandon Embedding Center's  cold plate is made out of cast aluminum and has a slightly "rougher" texture.
Could this produce a different way of conducting heat out of the paraffin block than the Shandon?
Perhaps the stainless steel draws heat from the blocks faster than the aluminum, and thus causes the cracking?

I have used the Shandon Embedding Center for over 24 years.
I have never had a problem with blocks that crack.

Thanks for any thoughts that you may have on this.

Tim Wheelock
Harvard Brain Bank
McLean Hospital
Belmont, MA


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