Thick sections challenge mounting media to remain intact, without retraction
(i.e., air under the cover glass), because the thick edge seal along the
perimeter allows solvent to evaporate more rapidly than it would with thin
sections.  The plastic resin cannot form a barrier, so air creeps in.  There
are three obvious potential solutions:

1)	Change to a mounting medium that has a lower proportion of solute.
Unfortunately, without doing weight loss experiments on your own, you
probably won't get the desired weight/volume information from the label on
the bottle of mounting medium for comparison.  You can always try asking the
vendor for the information.  Whoever makes it knows the answer.

2)	Use less mounting medium.

3)	"Cook" the covered slides.  Cooking slides originated in the lab of
the late Dr. Ruth Graham in the 1950s.  Freshly covered slides are set on a
hot plate, covered with aluminum foil for easy subsequent clean-up, set to a
temperature slightly above the boiling point of xylene (the usual solvent).
As I vaguely recall, that's about 117 degree C.  As soon as the mounting
medium begins to boil in a few seconds, remove the slide and set it on a
work bench.  Use forceps to tap out the bubbles, square the cover glass on
the slide, and clean with xylene.  It's messy, but it solidifies the
mounting medium immediately, reduces its thickness so microscopic
examination with high numerical aperture objectives is optimized, and
promotes long-term dye stability.

Gary Gill

-----Original Message-----
From: louise.marks@syngenta.com [mailto:louise.marks@syngenta.com] 
Sent: Wednesday, September 01, 2004 5:34 AM
To: histonet@lists.utsouthwestern.edu
Subject: [Histonet] drying out of sections



Dear All,

I am having problems finding a suitable mountant to use on quite thick (40
micron) free floating stained sections mounted onto slides. The mountant I
currently use, DPX, appears to be OK for the first few months but then
sections appear to 'dry out'- air forms round the edge of the section then
moves over the surface. I am after some advice on a good mountant to use on
sections for long term storage and any other tips to prevent this drying
out..best storage conditions etc. I use the slides for stereology at 100x
magnification so I would need a mountant that would be compatible with
microsopy,

Any tips / info much appreciated,

Regards

Louise

Dr Louise Marks
Syngenta
CTL
UK

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