Re: GMA Block Trimming

From:Gayle Callis <>

I always used a new glass knife for every block, and to trim, the used
glass knife did that job, switched to a new glass knife for sectioning a
just trimmed block.  You can cut GMA with tungsten carbide knives, D
profile, longer total working edge for a larger block face.   

We used Ted Pella teflon coated razor blades.  This cut GMA like butter,
for trimming sides of block down to shape you want, the teflon permitting
smooth, even, unshattered slices.  The block moved nowhere during this
process, used a magnifier to see what was happening. The technic was to
trim the block face the same way EM techs have shaped epon blocks for eons,
cut away from you, holding the blade between fingers but with a block
holder that cannot move.   Grinding and sawing is terrible with GMA.  Also,
I hope you wear safety glasses and a mask to prevent breathing fine dust.

Believe it or not, there are meat cutters gloves that are finer than some
bulky safety gloves I've seen.  Meat processing workers use these, and they
were cheaper than medical suppliers.  I do not recall the companies. Will
try and check on who sold those, huge selection.


At 01:55 PM 5/22/01 -0400, you wrote:
>Dear Histonetters,
>      I need help with my GMA block trimming ( please excuse typing as I
>trimmed 2 of my fingers a little bit, the tips of them). Currently I have a
>holder for my block and I set it in the holder and trim the excess off to a
>point for cutting on a rotary microtome at 2 microns. I usually use glass
>knives for research and now some times use a diamond knife for the clinical
>skin graft biopsies I do. Most of my blocks are 2x15x5mm and I use 6x12x5mm
>for the punch biopsies I get back from grafting sites, as they do not fit in
>the other molds. The Occupational Health Nurse wants me to find another way
>of trimming my blocks. I use a razor to trim them now. I have cut myself one
>other time when  I hit an air bubble. I have been doing GmA's since July of
>1996.  This is how I was shown and the only other way I know about; I've
>read about.  It is to use is a fine saw.  In reading ,I read that the dust
>is very bad for you. Is this correct?  My work load of blocks since starting
>is as follows 1996-- 100 blocks, 1997--580 blocks, 1998---980 blocks,
>1999--1300 blocks, 2000---915 ( my processor broke down in November), and so
>far 2001 I have 610 blocks. I have look at Kevlar gloves but I don't know
>that I can hold a razor blade and the block stable in the holder with such
>bulky gloves. Are there any non-bulky Kevlar gloves?  What ways do any of
>you trim your blocks. Should I stop trimming the 2x15x5mm and just let there
>be whatever vibrations there are upon hitting the glass knife and let it
>travel thru the whole block?  I still need to trim down the 6x12x5mm to fit
>my glass knife as it  isn't that big. I have tried sawing in the pass once
>before and remember the dust being very fine and all over everything and
>hard to cleanup. As I am the only one in this lab I have no one else to ask,
>so I thought you might be able to help with some ideas.
>  If you have any questions, please let me know. Thank you for any help you
>can give me.
>       Gail Macke,HTL
>        Shriners Hospital for Children: Shriners Burns Hospital--Cincinnati,
>Ohio, USA
Gayle Callis
Histopathology Supervisor
Veterinary Molecular Biology
Montana State University - Bozeman
Bozeman MT 59717-3610

406 994-6367
404 994-4303 (FAX)

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