We always surface seal our blocks prior to storage.  It seals in all the
moisture or out all the moisture.  It protects the tissue from any "bugs",
"germs" and any other "stuff" that might affect them.  We find that being a
research facility we go back to OLD (and I mean old) blocks all the time
and they perform as if they had just been processed yesterday.  The only
negative we have experienced is that some people hold the block too long in
the sealing paraffin and actually melt the block's paraffin, which causes
the refacing of the block to lose alot of good tissue before you can get a
nice specimen.  Also, we have a large variety of tissues: from mice to
elephants and from brain to thyroid; being processed at the same
time.  Obviously all of these tissues have different parameters for their
optimal processing.  We have one processor and have to process almost
everything at the same time.  We have chosen to over dehydrate "some"
things in order for the items that need more dehydration to be properly
infiltrated.  Therefore, without optimal dehydration on some things and
without sealing the blocks surface you will get alot of moisture give and
take between the tissue and the atmosphere of the storage area.  I hope
this has been helpful in some small way.





>Date: 26 Jan 2000 20:40:11 -0600
>From: TODD LUA <tlua@sierrabiomedical.com>
>Subject: Dipping blocks
>
>Hi,
>
>I would like to find out who out there is dipping the face of there
>paraffin blocks before storage.  If anyone has some pro's and con's about
>this practice and if it is really necessary to preserve the block in any
>way.  Thank you in advance for your comments.
>
>
>Todd
>
>*******************************
>Todd B. Lua, HT., (A.S.C.P.)
>Histology Laboratory Supervisor
>Sierra Biomedical, inc
>587 Dunn Circle
>Sparks, NV 89431
>Tel: 775.331.2201 ext.156
>Fax: 775.331.2289
>e-mail: tlua@sierrabiomedical.com
>*******************************