[pure-silver] Re: Vitamin C and Hydroquinone?
- From: titrisol <titrisol@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Mon, 31 Jan 2005 07:21:22 -0800 (PST)
Jerry,
thanks I'm aware of this adjustment. I have erythorbic acid,
not erythorbate.
What I do is "neutralizing" it with Na-Carbonate beofre adding
the development agent. (1.1 carbonate -> 1 acid)
--- "Koch, Gerald" <gkoch02@xxxxxxxxxx> wrote:
> Be aware that sodium erythorbate (CAS # 6381-77-7) exists as
> the monohydrate.
> Thus, some adjustment in weight must be made when using it in
> formulas that call
> for sodium ascorbate anhydrous. You will have to use 9% more
> of the erythorbate
> salt.
>
> Jerry
>
> -----Original Message-----
> From: titrisol [mailto:titrisol@xxxxxxxxx]
> Sent: Saturday, January 29, 2005 12:26 PM
> To: pure-silver@xxxxxxxxxxxxx
> Subject: [pure-silver] Re: Vitamin C and Hydroquinone?
>
>
> Thnaks Richard and Ryuji,
> you have answered my questions and given me more info.
>
> I have access to erythorbic acid, which for meat processing
> (and I assume
> photography) purposes works as well as Vit-C So I want to try
> search/work with
> this P-C developers.
>
> Thanks a lot!
>
>
> --- Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
>
> >
> > ----- Original Message -----
> > From: "titrisol" <titrisol@xxxxxxxxx>
> > To: <pure-silver@xxxxxxxxxxxxx>
> > Sent: Friday, January 28, 2005 10:22 AM
> > Subject: [pure-silver] Vitamin C and Hydroquinone?
> >
> >
> > > Hi all,
> > > I've been following the ascorbic developers attently, for
> > > a
> > > while, and have tried "perverting" rodinal succesfully.
> > >
> > > I've seen that most developers are either Phenidone-C or
> > > Metol-C
> > > but I haven;t seen any Hydroquinone-C developers.
> > > Can someone clarify why? or guide me to a resource on this
> > > topic?
> > > - Is there anatagonism between these 2 agents?
> > > - Do they act similarly?
> > > - Is ascorbate enough with phenidone?
> > >
> > > Thanks
> > >
> > Hydroquinone and Ascorbic acid have similar functions in
> > developers. Together with Metol or Phenidone they act in a
> > way that is known as superadditive. The combined developers
> > are more efficient and long lived than either alone. The
> > chemical relationship is complex but even where the
> > Hydroquinone is inactive as a developing agent, as in D-76,
> > it still acts to regenerate the Metol. Hydroquinone and
> > Ascorbic acid are not antagonistic but do not mutually
> > support each other to become superadditive. Also, neither is
>
> > a good general purpose developing agent on its own. The only
>
> > developers using Hydroquinone as the exclusive agent are
> > extremely high contrast developers used for photomechanical
> > work.
> > I am not sure what you mean in the last question. If you
> > mean does the combination of Phenidone and Ascorbic acid
> > form a good, practical, developer, the answer is yes, and it
>
> > does not need the addition of a third agent.
> > Metol is a good developing agent on its own, as in D-23
> > or D-25, but D-23 has a more limited capacity than D-76
> > where Metol is combined with Hydroquinone. Phenidone is a
> > very low contrast developer on its own as in POTA. It needs
> > the help of another agent like Hydroquinone or Ascorbic acid
>
> > to become useful as a general purpose developer.
> > p-Aminophenol, the active ingredient in Rodinal, is
> > similar to Metol but inferior to it as a sole developer. It
> > is used in Rodinal because it is soluble in sufficient
> > quantity to make highly concentrated stock solutions. It has
>
> > not been exploited in non-concentrated developers because
> > other agents, particularly Metol, are superior to it. About
> > the only non-concentrate formulas are substitutes for Metol
> > where there is a concern about Metol poisoning. Those with a
>
> > sensitivity to Metol will do better with Phenidone and
> > Ascorbic acid developers, which are not sensitizing and are,
>
> > in general, better developers.
> >
> > ---
> > Richard Knoppow
> > Los Angeles, CA, USA
> > dickburk@xxxxxxxxxxxxx
> >
> >
>
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>
>
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