I agree with Jeanne. I too, prefer the metal molds. I reuse the molds until 
they start to become "sticky", then I clean, dry  and spray with mold 
release. I don't deep track of specifically how often I clean them (maybe 
2-3 times per year), but it is definitely not necessary to clean them after 
every use.  I just put them back into the heat chamber and reuse.

LuAnn Anderson HT(ASCP)
Neuropathology Lab
University of Minnesota



At 01:14 PM 12/16/03 -0500, Bartlett, Jeanine wrote:
>"urn:schemas-microsoft-com:office:office" xmlns:w = 
>"urn:schemas-microsoft-com:office:word" xmlns:st1 = 
>"urn:schemas-microsoft-com:office:smarttags">
>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@lists.utsouthwestern.edu 
>[mailto:histonet-admin@lists.utsouthwestern.edu] On Behalf Of Morken, Tim 
>- Labvision
>Sent: Tuesday, December 16, 2003 12:59 PM
>To: histonet@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:
>
>Disadvantages:
>
>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 warped)
>
>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 advantage)
>
>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).
>
>
>
>Advantages:
>
>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 remove)
>
>
>
>
>
>Metal:
>
>Advantages
>
>Very low cost, last forever
>
>Flat face
>
>Cool fast
>
>
>
>Disadvantage
>
>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@mail.mcg.edu]
>Sent: Tuesday, December 16, 2003 7:56 AM
>To: histonet@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.
>
>
>
>Thanks
>
>
>
>Richard B Hessler, MD
>Chief, Section of Anatomic Pathology
>Associate Professor of Pathology and Neurology
>The Medical College of Georgia


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