From: Richard Knoppow (dickburk@ix.netcom.com)
Date: 02/16/01-01:35:02 AM Z
At 12:04 AM 02/15/2001 -0500, you wrote:
>At 2001/02/14 11:06 PM -0500, you wrote:
>>Hi Richard... do you know much about cellulose nitrate -- where you get it
>>for instance, how you spread it -- and solvent? I've been wanting to try
>>it for something else but so far didn't find much...
>
>Jumping in here. Cellulose nitrate is guncotton. To make a coating, it is
>dissolved in ether and a plasticizer (old-timers used camphor) added. The
>liquid emulsion is flammable and the dry product (celluloid) is explosive.
>Personally, I wouldn't touch it. Film base used to be made of this stuff,
>but it was substituted with cellulose acetate (whole different story) and
>that has been substituted in turn (by most manufacturers) with mylar and
>other plastic films, which are easier to handle as they are not hazardous
>materials requiring all kinds of precautions.
>
>If you want to make a cellulose nitrate coating, be sure you do it in a
>fume hood (ether is an anesthetic, as you know) with a great big fire
>extinguisher handy.
>
>
>Sil Horwitz, FPSA
>Technical Editor, PSA Journal
>teched@psa-photo.org
>silh@earthlink.net
>Visit http://www.psa-photo.org/
>Personal page: http://home.earthlink.net/~silh/
>
I mentioned cellulose nitrate only becuase it was one of the materials
used as a substrate for coating both glass plates and acetate film base. It
is certainly dangerous stuff, very inflamible and explosive under some
conditions.
I also mentioned hard gelatin, which was also used. This is simply
gelatin treated with some hardener, like chrome alum, which results in
harder a harder than usual condition.
Getting emulsion to stick to glass plates can be a problem. I have no
idea what Kodak currently uses. Its pretty easy to get the emulson off of
glass plates, sometimes just a long water soak will do it. In fact, this
can be used to salvage broken or cracked plates by floating the intact
emulsion off the cracked stuff and onto a fresh piece of glass.
---- Richard Knoppow Los Angeles,Ca. dickburk@ix.netcom.com
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