[Histonet] hard vs. soft paraffin

[Rene J Buesa]

Besides some additives that all paraffins have, "hard" paraffin is one that, as you point out, has a melting point (MP) of about 63ºC. There are even "harder" paraffins with MP of up to 70ºC and usually are more white in color.
The "normal" paraffin has a MP of about 53-55ºC, and soft paraffins are of less than 50ºC, usually about 43-45ºC.
The temperature of the water bath has nothing to do for paraffins above 50ºC and is usually always at about 45ºC.
Sections of very soft paraffins should be extended in water baths at room temperature and usually are very difficult to work with.
The harder the specimen, the higher the MP of the paraffin should be. Plant materials, specially twigs and branches to be cut transversely, require the hardest of the paraffins.
Ideally the paraffin should have a hardness to coincide with that of the tissue.
René J.

--- On Mon, 3/19/12, Clare Thornton <CThornton <@t> dahlchase.com> wrote:


From: Clare Thornton <CThornton <@t> dahlchase.com>
Subject: [Histonet] hard vs. soft paraffin
To: "'histonet <@t> lists.utsouthwestern.edu'" <histonet <@t> lists.utsouthwestern.edu>
Date: Monday, March 19, 2012, 2:13 PM


What constitutes "hard" paraffin vs. "soft" paraffin?  Is it just melting point?  What are the characteristics of hard and soft paraffins?  How does water bath temperature play a role?  Which is preferable for avoiding compression of tissue?

thanks,
Clare

Clare J. Thornton, HTL(ASCP), QIHC
Assistant Histology Supervisor
Dahl-Chase Diagnostic Services
417 State Street, Suite 540
Bangor, ME 04401
cthornton <@t> dahlchase.com

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