-- [ From: Garber, Charles A. * EMC.Ver #3.1 ] --

Mark Tobin wrote:
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Has anybody heard of a material called Collodion being used for mounting
materials for microscopy?  I was asked by a colleague today and have not
heard of it.

Any information, UK suppliers in particular, would be greatly appreciated ==
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Collodion  is manufactured by nitrating with nitric acid and sulfating with
sulfuric acid relatively ordinary cotton to make it soluble (as a result of
the addition of soluble nitrate and sulfate groups). When dried, the
solids become what is known as "gun cotton" because of its use as gun powder
. We believe that Parlodion  is very similar but it does have a different
corporate and process origin and it unlikely to be exactly identical. At the
very least, one could expect that the degree of nitrating and sulfating
might vary between the several different manufacturers, thereby resulting in
at least some subtle variation in the final properties. This could of course
help explain why one researcher might have difficulty repeating someone
else's work. However, most
researchers report obtaining similar results, whether the application is for
the casting of a film for TEM grids or for the making of replicas on
metallurgical or ceramic types of surfaces.

We believe Collodion to be similar but not necessarily identical to the
products called "Celloidin" and also, "LVN" , or "low viscosity
nitrocellulose".   And all of the mentioned products are supposed to be less
explosive than the original "gun cotton".

These materials, e.g. all of the above mentioned products based on
nitrocellulose nitrate, at one time, were also used widely as embedding
resins, but have been replaced in most applications by more modern
materials. However, for the embedding of really large samples, a technique
called "double embedding" still requires a nitrocellulose type material.
However, for specific kinds of samples, there might be a preference for one
or the other of the nitrocellulose based materials.

Collodion, as well as the sister nitrocellulose based materials are
flammable solids and require great care in their handling.

Disclaimer:  SPI has offered both Parlodion and Collodion in both solid form
as well as in solutions of 2% in amyl acetate for a long time.  Both the
solid material or solutions can be ordered either directly from SPI in the
USA or from our distributor in the UK listed on our website.  Our interest
is to make sure that people understand that generically, these materials
seem to be similar and while it is to the first approximation, if you have
one "in hand", then you already have something that is very close to the
other.  Our other interest is to remind everyone that these are trade names
of manufacturing companies and first use on a page should include the use of
a "TM".

Chuck

===================================================
Charles A. Garber, Ph. D.                    Ph: 1-(610)-436-5400
President                                         1-(800)-2424-SPI
SPI SUPPLIES                                  FAX: 1-(610)-436-5755
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