In response to the query about plastic coplin jars - I have been working 
with coplin jars and heat (ie microwaving) for over 20 years.  During that 
time I have found there is a world of difference in glass coplin 
jars.  There are no Pyrex jars at the present time.  However, the glass 
that we get are different grades.  If you are going to heat your coplin 
jars to 55C or above here are some tips.
	When you buy the jars, buy Wheaton brand.  They are the ones with the 
square bottoms.  They are thinner glass (and a better grade) that the round 
bottomed jars that are sold by most scientific companies.  I buy mine from 
Fisher (cat # 08-813E).  As Gayle said, any time you are using glass, do 
not heat quickly and enclosed the jar in a zip-type bag.  The difference 
between the round and square bottomed jar is the thickness of the 
glass.  The round have thicker glass which heat a different rates and 
cracks easily.
	May I also suggest that you buy some square, plastic slide jars - the kind 
that hold 8 (to 15) slides.  These are made to microwave and work really 
well  and are have a light tint to them but it does not interfere with 
seeing the slides if that what you want.  You can get these through VWR and 
Histology Control Systems.  (There are other vendors.)

Cheryl Crowder