U of S | Mailing List Archive | alt-photo-process-l | Re: LC-1 developer question

Re: LC-1 developer question

I don't know about silica. It's used as matting agent in film
coating (to reduce friction in the film path in cameras), but
it's not trouble free because some of them go into the
processing solution and settle in the tank. I wouldn't add
things like that to processing solutions.

When used in varnish or emulsion coating or something of that
nature, there is at least some peptizer (such as gelatin) to
hold the particles in the dispersing media, but not when
mixing D-76.

I don't think they've done much when they package ingredients
together. Metol wouldn't have much problem dissolving in
Dektol, it just may take a bit longer to dissolve.  It may be
difficult to dissolve in D-76 at its high sulfite content and
low pH, but then the Metol content is only 2g/l.

If they have added anything to aid forming fine granules, a
common material for these things is sorbitol or similar
material. But then the bulk of the powder will increase

One thing is that they may have changed the form of Metol from
crystal to fine powder.

Anyway, the reason I'm interested in formation and growth of
crystals in supersaturated solution is because it is of
fundamental importance in silver gelatin emulsion making. Not
very interested in making concentrated Metol developer, as you
see my favorite developing agents are isoascorbate and
Dimezone S.

Ryuji Suzuki
"Make something religious and people don't have to deal with it, they
can say it's irrelevant." (Bob Dylan, Biograph booklet, 1985)

From: Richard Sullivan <richsul@earthlink.net>
Subject: RE: LC-1 developer question
Date: Sun, 30 Mar 2008 08:55:02 -0600

> Fused silica. That's my guess. It's in submicron sized
> particles, (measured in nanometers!) and is used to thicken
> stuff like varnish and also to keep powders of mixed
> chemicals from separating out, such as the heavy stuff going
> to the bottom. It's inert and invisible when in solution. It
> may also keep crystals separated so they don't interact
> which is the possible answer here. I believe it is the magic
> stuff in "powder free" latex gloves. Talc is huge in
> comparison so I think they can call it powder free when
> used.