Paula
This problem can most often be traced back to a simple oversight.  First
you should be using one of the so called charged or Plus slides as they
work the best and give very dependable results ( we use Fisher Brand ).
Poly L lysine coated slides work, but are not as good or as dependable in
our hands.  Secondly, always mount your sections from DIST WATER.  Many
techs make the mistake of  mounting their sections from water baths to
which they have added an adhesive such as gelatin etc.  Most of these
adhesives are formulated in part from a protein, so when a coated slide is
first dipped into the water bath the adhesive immediately occupies all the
binding sites on the glass slide leaving none behind to bind to the tissue
section once it is mounted.  When heated in a hight temperature steamer
etc., the protein adhesive breaks down and lets the sections fall off.
Hope this solves your problem.
Kerry Beebe  (ART)
Kelowna Gen Hospital
Kelowna B.C. Canada
bbracing@silk.net