Dear Jill,
	A couple of questions, please.  # 1 - Do embryonic chick heads
contain any calcified areas?  #2 - Are you using embedding rings with your
paraffin blocks?
	You can buy  "Peel Away Disposable Embedding Molds"  in a variety
of sizes from most EM suppliers.  One in the U.S. is EM Sciences 1-
800-523-5874.  I use the 22 x 40 mm size and, after mixing up the glycol
mixture (LR White), I place the specimen in the bottom of the mold, pour on
glycol, allow mixture to become "gummy" and float an embedding ring on top,
allow to solidify.  You can then attach the block to the microtome by the
embedding ring (creative embedding technique #3).
	Back to # 1 question -- if the answer is no then you are ready to
section.  If yes, then, a regular microtome knife "ain't gonna cut it" (pun
intended) or you may need to consider decalcification.  There are
specialized tungsten-carbide blades for sectioning calcified blocks.
	As to the correct mixture of LR White, I would recommend that you
try 2 -3 different recipes and polymerize in the above technique and try
sectioning.  See which serially sections with ease at 4 -5 microns and use
that recipe.
	Good luck!
	Linda

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Linda Jenkins, HT
Clemson University
Department of Bioengineering
Clemson, SC
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