In three lab over the past 20 years I have occasionally come across
the following mountant problem.
After about three or four months globules appear in mounted slides.
These globules disappear on heating and are seen less near the edge
of the coverslip.
Slides which have been air dried on a hot plate before mounting, i.e.
have no trace of alcohol or water on them, have the same problem as
those from a linistain or dehydrated by hand.
Dipping the slides in xylene rapidly removes the globules from the
edges of the coverslip.
I have used BHD, Cellpath and Surgipath mountant and have had the
same problems.
When looking at the globules down the microscope they do not deform
when the coverslip is poked with forceps. 
Any ideas what is causing this?

Best Wishes

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