Re: WTB: UNUSED K-12 or K-14 process film. (135, 120, super 8/double 8, etc), bulk, 70mm EIR, etc.

From: Alex Swain <fotoobscura@gmail.com>
Subject: Re: WTB: UNUSED K-12 or K-14 process film. (135, 120, super 8/double 8, etc), bulk, 70mm EIR, etc.
Date: Tue, 01 Feb 2005 23:49:07 -0500

> This is a good point and I have researched the USPTO ...what do you
> think about doing this? Have you done it? I am excited to try it.

I think that formula is generally good as an old time negative
emulsion. The formula given as an example is pretty specific except
that it doesn't give temperature and time, and maybe a few other
things. If you are serious, I can get my notes and fill these in for
you.

I've made many emulsions like that but with different variables. It
was a sort of introduction to bromide emulsion making. My current
negative emulsion is more complicated than that, in terms of
ingredients and steps. One difference is the way the sensitivity is
increased. Another difference is about productivity of the noodle
washing process. The whole part of chill setting, noodling, and
washing part is replaced with a chemical treatment that makes gelatin
temporarily separated from the water phase. This allows me to decant
off the salt solution and wash the silver-gelatin sediment in cold
water a couple of times (since the gelatin does not swell at all,
rinsing twice is sufficient), and make the gelatin soluble again. A 5
hour washing labor is replaced with an about 20 minutes operation. But
this is more like a 1960 technology that doesn't suit your request.

At the AGFA Wolfen plant in 1940s, the emulsion was set in pans of
8x100cm where emulsion was filled about 4cm deep. The emulsion jelly
was slit into 1x1x4cm sticks (more like freedom fries than noodles)
and washed in cold water for 5 hours. If you use a cheesecloth to make
thin noodles, or food processor to make flakes, washing can be done
faster. But avoid making fine particles.

I think other parts are straightforward but feel free to ask questions.

--
Ryuji Suzuki
"People seldom do what they believe in.  They do what is convenient,
then repent." (Bob Dylan, Brownsville Girl, 1986)