The persistence of a problem despite many "solutions" is often an indication
that the underlying fundamental cause has not been identified.  In the case
of tissue sections adhesion is promoted by mutually attractive surfaces
(i.e., opposite electrical charges) in contact with one another.  Tissue and
glass are naturally attractive under the right conditions.  Specifically,
the glass must be squeaky clean and the tissue must lie flat against the
glass.  Folds can contract during fixation and help separate the sections.

To make glass wettable, simply immerse slides in alcohol and wipe dry with
clean cheesecloth immediately before use.  Precleaned and/or coated glass
will naturally adsorb electrical atmospheric/particulate charges over time
and become less wettable (hence Jeff's remark that "Positive-charged slides
can deteriorate with age").  Using this method in cytology results in good
cell recovery and flattening.  This method is better than frosted slides,
albuminized slides, albuminized cell buttons, poly-L-lysine coated slides,
etc.  BTW, moisture that naturally condenses between packed slides over time
interacts with the silica and forms HCl, which etches the glass and leaves
the whitish deposit we see, furthering reducing attractive forces.  Thus,
Clay Adams began packaging its slides in hermetically sealed wrap with
silica gel packed inside many years ago.  Cover glass manufacturers followed
suit and include small packets in the 1-oz plastic containers.

Gary Gill