[pure-silver] Re: Coating Glass Plates
- From: Ryuji Suzuki <rs@xxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Thu, 27 Jan 2005 18:23:10 -0500 (EST)
From: DarkroomMagic <info@xxxxxxxxxxxxxxxx>
Subject: [pure-silver] Coating Glass Plates
Date: Thu, 27 Jan 2005 23:57:32 +0100
> Who can point me to some literature, or who knows what to watch for?
Easiest way I've found so far is wire wound coating rods.
> Here is what I like to learn:
>
> 1. Does the glass need special cleaning?
Decent degreasing would do. Windex works, dishwashing detergents
works if you work thoroughly, classic soda bath works. I use a soft
sponge saturated with a 2% carbonate solution with a bit of
surfactant.
> 2. What type of glass is best?
If you aren't using it as a negative, it doesn't matter much, I
suppose. Decent float glass would do. 1/15 inch (1.6mm) is standard
for negative plates of standard size or smaller.
> 3. What type of gelatin will do?
If you want to optimize the adhesion, use lime treated gelatin. 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.) and normal gelatin of large average
molecular weights, hardened with glutaraldehyde,
2,4-dichloro-6-hydroxy-s-triazine, epoxides, active vinyl compounds,
etc. that crosslink at amino residue of lysine. This type of gelatin
mixture with a bit of good surfactant sticks to glass like a suction
cup even before drying, after gelling, of course. Generally, increased
available carboxyl groups improves adhesion.
> 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.
> 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.
--
Ryuji Suzuki
"Keep a good head and always carry a light camera."
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