From: Kate Mahoney (kateb@paradise.net.nz)
Date: 09/05/03-03:26:01 PM Z
----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Saturday, September 06, 2003 9:11 AM
Subject: Re: coating method
> 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...
Thanks Ryuji, I will do this!
> --
> Ryuji Suzuki
> "Reality has always had too many heads." (Bob Dylan, Cold Irons Bound,
1997)
>
>
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