Marilynn,
You do not detail you fixation/processing protocol, so I have to make the assumption that you are processing your biopsies the same day you recieve them.
In my experience, nuclear bubbling or foaming, is a result of processing the biopsy specimens befor they are adequately fixed in 10% formalin.  Tissues to be fixed in 10% formalin, regardless of size, require  a minimum 24 hours to fix, before they can be processed without causing formalin fixation artifact (foaming or bubbling of the nuclie).  One way to check to see if this is the problem, is to examine a few biopsies that fixed in 10% formalin over a weekend, before they were processed.  These should not show this artifact. If they do, then you should look at the formalin you are using or the collection method.  We use recycled xylene with no problems what so ever, so it should not be part of the problem.
In my lab, where turn around time is also important, and same day processing is the norm,  we switched to a modified formol acetic acid alcohol fixative, years ago, for all our biopsies, to avoid this problem. This fixative gives beautiful nuclear and cytoplasmic details, fixes the specimen in only a couple of hours, and significantly enhances most immunohistochemical stains, in particular the so called Keratin 903 stain that we do on the prostate biopsies. (L26 and S100 are about the only two antigens not well preseved).  The formula that we use is as follows, 100% ethyl alcohol -210ml. Con Acetic Acid -15ml. 40% formaldehyde-30ml. Distilled water -45ml. We suply this fixative to the biopsy O.R.s  so that the tissues are placed into it as soon as they are taken.  Hope this is of some help.
Kerry Beebe
Kelowna Gen Hospital
Kelowna B.C. Canada
bbracing@silk.net