[Histonet] Cooling paraffin blocks with ice VS. Freezing Spray

[Jackie O'Connor]

It has been my experience that using freezing spray will cause artifacts in the paraffin block as well as the tissue.  We are a high-throughput lab where all the techs face all their blocks then put them on a block of wet ice prior to microtomy.  I am not a fan of freeze sprays, personally.  Free ice is much cheaper than a can of spray.  
Jackie O'


-----Original Message-----
From: Jenny Vega <histotech411 <@t> gmail.com>
To: histonet <histonet <@t> lists.utsouthwestern.edu>
Sent: Fri, Sep 28, 2012 9:40 pm
Subject: [Histonet] Cooling paraffin blocks with ice VS. Freezing Spray


I want to know what is your preferred method for cutting paraffin blocks in
the microtome everyday. At work I am having issues with my supervisor
because we have different ways of doing things like for example she doesn't
like to use the technique where you first trim the tissue, cool it on an
ice tray and then make a section. That is how I learned to cut in histotech
school. Instead she just trims and cuts the blocks at 4 microns one by one
using the same blade until it wears out and she cools the blocks only
freezing spray.

She doesn't like to cool the blocks on an ice tray because according to her
is a waste of time and that is why I have to use her technique but
unfortunately some blocks are extremely difficult to cut and I have to go
back to my preferred  technique. I feel I get better sections without
wrinkles when I chill and soak the blocks on ice for a couple of minutes. I
sometimes use freeze spray when the blocks get warm but when I cool them
with ice I don't need to use freeze spray that much. Her technique works
but is more successful when the blocks are well processed. I have
difficulty getting completed sections  this way and spend more time trying
to get the perfect section. Sometimes I have my good days but other times
is tedious using this technique. Another thing I notice is that the blades
get worn down quicker when you use them to trim and section. I prefer two
separate blades, one to trim and the other one to section. I feel they stay
sharp for more time.

She discourages the use of ice but then complains that we are running out
of freezing spray for the frozen sections too quickly which doesn't make
sense. It is obvious that if she encourages to use ice to cool blocks then
we will be using less freezing spray.

Another reason she discourages the use of ice is that some blocks are not
meant to be chilled which is pretty understandable. I cannot cool small
biopsies such as gastric and skin and bone because they can get too hard
and tear off from the block so I avoid that but I prefer to cool breast and
colon biopsies on ice because these are fatty tissue that can be tedious to
cut even when relying only on freezing spray.



I want to know if it's completely acceptable for me to prefer the trim,
cool on ice and section technique and if you feel is a waste of time
comparing it with other ways of cutting such as the one I mentioned.



Thanks.
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