Re: paraffin sections turning white

From:Mary North

In my experience, this happened when the trimmed block face was not rehydrated sufficiently on tissue that was over-dehydrated in the processing schedule. It was more prevalent in small biopsies which tend to get overprocessed. A cotton ball or Kimwipe soaked with warm water and held onto the block face will rehydrate better than the cold ice cube or water.  A pad soaked with a dilute solution of Tween 20 held on the block face will rehydrate even better, if necessary, but take care not to oversoak the face or the tissue becomes too soft to section. 
Mary North, HT(ASCP), HTL
Oregon Health and Science University
Portland, OR

>>> Jacqueline Miller <> 07/16/03 07:13AM >>>

I've been having trouble lately with the tissue portion of my paraffin sections turning white (either in patches or the entire tissue) and appearing really dry, even cracked.  The paraffin surrounding the tissue does not change appearance.  This type of tissue normally doesn't turn white.

The sections come off the microtome easily and are smooth, and when I first pick them up off of the water, they look fine.  But, after about 10 minutes or so, they start turning white.  The appearance varies some from section to section, and a few don't ever turn white.  I hope I've described this well enough.

An expert has told me that it is probably the processing, but I'm concerned because we have received blocks from many different sources.  This continues to happen with each block, and wasn't happening a year ago.  Has anyone experienced this problem before?  Does anybody have any ideas as to what I could be doing wrong?  Thanks.

Jacqueline Miller

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