[pure-silver] Re: Vitamin C and Hydroquinone?

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
> > 
> >
>
================================================================================
> =============================
> > To unsubscribe from this list, go to www.freelists.org and
> logon to 
> > your account (the same e-mail address and password you
> set-up when you 
> > subscribed,) and unsubscribe from there.
> > 
> 
> 
> 
>               
> __________________________________ 
> Do you Yahoo!? 
> Yahoo! Mail - Easier than ever with enhanced search. Learn
> more.
> http://info.mail.yahoo.com/mail_250
>
================================================================================
> =============================
> To unsubscribe from this list, go to www.freelists.org and
> logon to your account
> (the same e-mail address and password you set-up when you
> subscribed,) and
> unsubscribe from there.
>
=============================================================================================================
> To unsubscribe from this list, go to www.freelists.org and
> logon to your account (the same e-mail address and password
> you set-up when you subscribed,) and unsubscribe from there.
> 



                
__________________________________ 
Do you Yahoo!? 
Yahoo! Mail - Easier than ever with enhanced search. Learn more.
http://info.mail.yahoo.com/mail_250
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your 
account (the same e-mail address and password you set-up when you subscribed,) 
and unsubscribe from there.

Other related posts: