Re: Glycerin questions

From: Bogdan Karasek <bkarasek@videotron.ca>
Subject: Re: Glycerin questions
Date: Fri, 14 Apr 2006 00:52:33 -0400

> It's been a while since the last chemistry class. How is glycerin used
> in photography?

First of all, chemists call it glycerol to be consistent with naming
of other compounds. Like glycols, glycerol is a compound having
multiple alcoholic -OH groups (a polyol). These compounds usually have
names that end in -ol.

Glycerol is hygroscopic and so if it's added to some coated layer, the
layer retains moisture better. It may be added to silver-gelatin
emulsion so that the gelatin retains moisture. Otherwise, gelatin will
become too brittle at high temp, low humidity conditions. In this
sense, glycerol is used as gelatin plasticizer. (However, glycerol is
actually a poor choice for this. Dextran, sorbitol, etc. are better.)

Glycerol solution also appears in old formula books as a "print
flattener." Because of this humectant action, glycerol-treated print
retain moisture and they tend to be easier to make flat. However, this
is not a good idea from archival aspect and it is not recommended to
use such solution.

But Don probably has different uses for it.
Received on Thu Apr 13 23:09:40 2006