RE: microchatter

From:Pamela Marcum

Pricilla makes some very good points on why microchatter occurs.  Another
area often not considered is the fact that the block warms as it is
sectioned and thus expands and contracts depending on how cold the block
was and how warm it gets.  This is caused by the friction of the block
moving across the knife.  Re-cooling the block with an ice cube or (try not
to do this one to avoid other artifacts) using a freezing spray must be a
very even cooling to prevent the block from contracting with the cold
unevenly and creating more chatter.  If the block is too cold it will
chatter from the movement over the knife again due to the formation of very
cold spots in the paraffin.  WE get to attempt to figure out what is too
cold and when the block is too warm for sectioning and this is a very
delicate dance with the polymers in the paraffins today.  
Pam Marcum   

> [Original Message]
> From: Priscilla Delventhal 
> To: 
 > Date: 4/27/2002 8:33:44 AM
> Subject: microchatter
> Hi to all in Histo land.  I have read with interest the ever present

> problem of microchatter.  We seem to be honing in on many different

> techniques to help with this problem.  With everything that has been

> said, no one has addressed the friction that occurs from the passing of

> the knife over the paraffin block cut edge.  Faster cutting would

> increase this friction and a surfactant; i.e. water or soap, etc., would

> help to decrease this friction.  Also, I would think that the angle of

> the knife to the block would affect this friction.

> I know this doesn't solve the problem, but sometimes understanding what

> is happening helps.  I found it interesting that the polymers in the

> paraffin need time not cold to harden.


> Many years ago, I read an article in the Journal of Histotechnology

> about a solution called Baker's softening solution.  I made this

> solution up using less phenol and find that it helps with what I have

> always thought to be a friction problem.  Many techs don't want to take

> the time to soak their faced blocks, but I face all of my blocks and

> when I can, I soak in Baker's softening solution.  If I had no time

> constrictions I would do this all of the time as the sections are

> beautiful.  For blocks with calcium I use the softening solution 1:1

> with a decal solution.  I do cut with a slow even motion.


> This solution solved my problems with microchatter and when I cut deeper

> into the block without soaking the microchatter returns.


> For those of you that would like to try this solution, here are the

> directions.


> Modified Baker's Softening Solution (modified because the original

> directions called for more phenol).


> 720  CC of 60% ROH

> 80 CC Glycerol

> 20 CC Acetone

> 20 CC Phenol

> Mix well.


> This stuff smells great and feels good on your hands too.


> I surface the blocks, place them face up on the ice or cold plate and

> cover the surface with a paper towel soaked in Bakers solution.


> If you try this, I would appreciate hearing your thoughts on your

> experience with it.


> Priscilla Delventhal - Currently in New Hampshire on a traveling

> assignment.








--- Pamela Marcum
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