[Histonet] Plastic Embedding Molds

Bartlett, Jeanine jqb7 <@t> cdc.gov
Tue Dec 16 12:14:14 CST 2003

We use both in our lab and I prefer the metal molds for the reasons Tim
listed.  However, Tim mentioned one drawback of metal molds being the
time required daily to clean them.  Honestly, I find that cleaning and
treating once a year is plenty, if that often.  When I get new molds I
spray them with any spray-on mold release (not the kind you have to soak
the molds in) and that is usually sufficient.  When I treat some older
ones that have been previously used I run them through the clean cycle
of the VIP (I know that is a no-no but I don't do it often!) and then
apply the spray. I do not embed daily but when I was working at a small
local hospital years ago where I did embed daily I found
cleaning/spraying twice a year was sufficient.  So I don't think the
time involved in cleaning/handling metal molds is an issue at all.
Just my point of view!
Jeanine Bartlett, HT(ASCP)
Centers for Disease Control
Infectious Disease Pathology Activity
1600 Clifton Road, MS/G-32
Atlanta, GA 30333
	-----Original Message-----
	From: histonet-admin <@t> lists.utsouthwestern.edu
[mailto:histonet-admin <@t> lists.utsouthwestern.edu] On Behalf Of Morken,
Tim - Labvision
	Sent: Tuesday, December 16, 2003 12:59 PM
	To: histonet <@t> lists.utsouthwestern.edu
	Subject: RE: [Histonet] Plastic Embedding Molds
	Dr. Hessler wrote: "...what advantages do these have over
traditional steel other than you don't clean them? As steel basically
has an unlimited lifespan, are the disposable molds really cost
effective in a clinical laboratory."
	Plastic molds:
	Very high cost (although they can be reused for a while - just
don't store in the heated space of the embedding center or they get
	Hard to orient fragments due to some kind of electrostatic
forces that move the pieces around.
	Slow to cool - again hard to work with small fragments and skin
when you want to orient them a certain way. (though some may see as an
	Not as flat on the face as metal, so more trimming - bad for
very small specimens.
	Do not hold heat the way metal does, so cools faster on the
sides when time is spent orienting tissue. I see many more mis-oriented
tissues in plastic molds, and mis-oriented mold/cassette problems (block
face is mis-oriented to the cassette back, which means the block face is
at an angle in the microtome chuck...= more trimming).
	The sides of the mold are more vertical than the metal mold so a
bit easier to cut (smaller face, sharper edge)
	Easy to take off the block (metal molds are often difficult to
	Very low cost, last forever
	Flat face
	Cool fast
	Sometimes difficult to remove - use mold release (but that does
take time and requires cleaning the molds daily in xylene/alcohol - we
put them in the tissue processor and run the clean cycle)
	Cracked blocks? I haven't seen that as a problem. It is mainly
in large blocks. You can put them on a piece of paper over the cooling
plate to avoid that.
	It seems the only real advantage of the plastic is the shorter
time spent taking the mold off the block and avoiding the time it takes
to clean the metal ones (about 15 min/day max)
	If I was paying the bills I wouldn't get the plastic - they are
far more expensive and do not give as good quality face as the metal. 
	But...I haven't done a cost analysis of the plastic molds vs
time spent to clean metal molds and then soak in mold release every day.
	Tim Morken
	-----Original Message-----
	From: Richard Hessler [mailto:RHESSLER <@t> mail.mcg.edu] 
	Sent: Tuesday, December 16, 2003 7:56 AM
	To: histonet <@t> lists.utsouthwestern.edu
	Subject: [Histonet] Plastic Embedding Molds
	I would like advise about disposable plastic embedding molds.
Was wondering if any clinical labs had experienced problems with delays
and uneven tissue alignment due to static and slow heat transfer. Also,
what advantages do these have over traditional steel other than you
don't clean them? As steel basically has an unlimited lifespan, are the
disposable molds really cost effective in a clinical laboratory.
	Richard B Hessler, MD
	Chief, Section of Anatomic Pathology
	Associate Professor of Pathology and Neurology
	The Medical College of Georgia
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