Re: Cracks in Paraffin Wax Blocks

From:Sharron Ladd

Are you using metal molds? I learned in a NSH workshop, that leaving the 
blocks chilling too long on the cold plate (in metal molds) can cause 
cracks to form in the paraffin.

ncragg wrote:

>Dear All,
>Please could anybody tell me why I am getting cracks in my paraffin wax 
>blocks?  I noticed someone had asked this question a couple of years ago 
>but there was no reply posted.  I can still cut sections from these blocks 
>and they look fine under the microscope.  Not all the blocks in a batch are 
>cracked, some are nice and I've even had batches where 90% of the blocks 
>are good and only a few have cracks.
>We use Surgipath Formula R paraffin wax and I have spoken to the rep there 
>and he suggested a couple of things, but none have made any difference; he 
>has also checked the batch of wax we were using and there are no reported 
>problems; besides we are now onto another batch and the same thing happens. 
> I have wondered whether it is my embedding technique, but have tried many 
>different ways, e.g. different amounts of wax in the base mould before 
>orientation, different lengths of time on the refrigeration spot before 
>topping up and different methods of cooling, ie. using the coldplate and 
>-20 freezer.  I am also careful not to move the tissue once the wax starts 
>to solidify.  The wax is melted at 60 degrees celsius in the processor and 
>the embedding centre is also set at 60.
>I would be very grateful if anyone has anyone got any suggestions?
>Thanking you in advance.
>Nicola Cragg
>Epistem Ltd.
>Manchester, UK

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