From: Ryuji Suzuki (rs@silvergrain.org)
Date: 09/05/03-03:11:13 PM Z
From: Kate Mahoney <kateb@paradise.net.nz>
Subject: Re: coating method
Date: Sat, 06 Sep 2003 08:47:18 +1200
> Yes, I'm sure that's what it is - heating the glass helps a lot, stops the
> emulsion from coagulating while I'm applying it.
Ok, then diluting the gelatin isn't the best way to do...
> The glycerin is for what purpose???? Can you recommend an aldehyde hardener,
> otherwise I'll just use formaldehyde as the easiest to get - I have a fume
> cabinet btw.
First of all, be careful of aldehyde hardeners. I use glutaraldehyde,
but you put too much of hardener and the emulsion (or gelatin
dispersion for subbing) becomes as hard as rubber eraser and you can't
soften them by heating. When you add too much like this, the emulsion
and the brush are ruined. I take a small portion that is enough to
coat 3 pieces of paper or whatever and add a tiny bit of
glutaraldehyde solution and stir, then coat, to reduce potential risk.
A very small amount of it (just enough to increase the viscosity a
bit) is effective (I use a medical syringe of 1.0ml size for this
purpose). My solution is 2.5% (a product sold for sterilization of
surgical instruments that cannot be autoclaved).
Aldehyde hardners may make gelatin too brittle. I'm sure there are
better options around, but glycerin is a classic plasticizer to keep
gelatin flexible as well as hardened. I'd also add some wetting agent
like Triton X-100 or PhotoFlo 600. PhotoFlo 200 has propylene glycol
or something besides Triton X-100, so I'm not sure how it compares.
If the emulsion is hardened and plasticized just right, I don't think
subbing is necessary. After all, both are gelatin dispersion anyway.
Try some without subbing...
-- Ryuji Suzuki "Reality has always had too many heads." (Bob Dylan, Cold Irons Bound, 1997)
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