[pure-silver] Re: Coating Glass Plates
- From: Ryuji Suzuki <rs@xxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Thu, 27 Jan 2005 18:51:48 -0500 (EST)
From: Ryuji Suzuki <rs@xxxxxxxxxxxxxxx>
Subject: [pure-silver] Re: Coating Glass Plates
Date: Thu, 27 Jan 2005 18:23:10 -0500 (EST)
> > 3. What type of gelatin will do?
>
> If you want to optimize the adhesion, use lime treated gelatin.
Usually this alone gives good enough adhesion. The following was ment
as one good way to further improve adhesion. I personally use the
mixture of phthalated gelatin and normal gelatin, both from lime
treated ossein gelatin. Food gelatin is usually acid treated pigskin
gelatin of small molecular weight and they are vastly inferior in
terms of adhesion (and many other aspects). High MW pigskin gelatins
available from lab supply houses have good jelly strength and they are
usable for subbing and overcoats.
> I'd
> mix modified gelatin (e-amino residue is acylated with phthalic
> anhydride or trimellitic acid anhydride, see US patent
> 2592250. Trimellitic acid anhydride is generally superior, and it was
> subject of another patent a few years later, assigned to Polaroid, but
> works on the same basis.)
Forgot to say that these long expired patents were concerned about
simplifying desalting step of emulsion making and not about increasing
the adhesion of gelatin to substrates. But you can just follow the
examples therein to make modified gelatin and use it as a binder as
well.
> > 4. Do I need a hardener for the gelatin, and if 軽esケ, which
> > hardener?
>
> See above. Glut is easiest to buy and work with, except its
> volatility. 2,4-dichloro-6-hydroxy-s-triazine (subject of an old Fuji
> patent) is nonvolatile and easy to use, but I feel that its rate of
> hardening is more sensitive to concentration. Latter is also not
> commercially available and you have to synthesize it.
Also forgot to say that hardener is not absolutely essential,
especially if you can get good adhesion and the water wash temperature
is below 20C. But hardener is definitely a good insurance.
> > 5. How do I prevent bacteria grows, or is this not to worry about?
>
> Add about 0.1g of sodium salt of 2-phenylphenol, sold as Preventol ON
> extra flakes from Bayer, for each 100ml of solution. It's a very good
> bactericide with favorable toxicology profile and inert at least to
> silver gelatin emulsions.
Other options are phenol, thymol, methyl p-hydroxybenzoate,
p-chloro-m-cresol, pentachlorophenol, etc. But I prefer 2-phenylphenol
and I'd avoid those halogenated ones.
--
Ryuji Suzuki
"Keep a good head and always carry a light camera."
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