[Histonet] Polymer Paraffin

[Morken, Tim]

Russ has a good idea in going to "pure" paraffin, that is, without
additives, in order to see how non-additive paraffin works. Then
comparing to paraffin with additives may give an idea on what you need.
However, it is almost impossible to find out exactly what is being added
to these paraffins. Most manufactures are adding "resins" of some kind.
These are usually in the class of "thermoplastic" resins - those only
plastic at high temperatures (vinyls, styrenes, butyls, acrylates,
urethanes). As such, they are not plastic at room temperature. Indeed,
most of these resins are the same as those found in hot-melt glue, which
should give you an idea on how they will act. Some, if exposed to high
heat, may polymerize in a way that makes it impossible to remove them
from a section or slide. This may be why there is sometimes a
"background" of stain around a tissue that matches the area of the
original wax area of the section. Most of these add strength to the
paraffin, but some make it more "sticky"  so it "ribbons" better.  These
are added in percentages of 5 - 15% from what I can glean from their
literature.


Tim Morken
Lab Vison Products
ThermoFisher Scientific

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of John
Kiernan
Sent: Monday, October 01, 2007 8:34 AM
To: histonet <@t> lists.utsouthwestern.edu
Subject: Re: [Histonet] Polymer Paraffin

The most recent of Russ Allison's internet statements on paraffins may
be an FAQ answer:
http://publish.uwo.ca/~jkiernan/faqlist.htm#WAXCRY

John Kiernan
London, Canada.