[pure-silver] Re: Old Agra 120 Brown Black Developer {120 (Potassium Version) print developer}

Tim and Cor,

Once I was out of Sodium Carbonate and had Potassium Carbonate in house. I
called Steve Anchel and asked him directly. I remember him cautioning me
that the mixed solution would not last as long. The weight conversion seems
right. 

 

Eric Neilsen Photography
4101 Commerce Street
Suite 9
Dallas, TX 75226
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http://ericneilsenphotography.com
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> -----Original Message-----
> From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-
> bounce@xxxxxxxxxxxxx] On Behalf Of Tim Eitniear
> Sent: Friday, January 26, 2007 2:35 PM
> To: Pure Silver
> Subject: [pure-silver] Re: Old Agra 120 Brown Black Developer {120
> (Potassium Version) print developer}
> 
> Cor,
>     To your point, I did some research on the chemical conversions I found
> the following two posts.  In fact Lloyd's name was associated with the
> posts.
> 
> 
> I made the remark; it originally came from The Darkroom Cookbook,
> concerning
> potassium carbonate, and I extended it to sulfite.  The latter is
> available
> from Photographer's Formulary at $16/lb.  It doesn't specify the hydration
> status; the ratio of K2SO3 to Na2SO3 is 158/126, or about 1.25.  I believe
> that the ratio of the carbonates is one of the hundreds or so errors still
> in the darkroom cookbook (the "corrected" edition); K2CO3/Na2CO3.H2O  is
> 138/124, so DIVIDE, not multiply, the amount of sodium carbonate by 0.9 to
> substitute the potassium version.
> I recently did a series of tests on Agfa MCC using warm and cold
> developers,
> substituting only the carbonate, not the sulfite; and potassium makes a
> final print that is noticeably warmer, especially after sepia toning.  I
> plan to mix the developer with both potassium salts next time I use a warm
> developer; I guess I or someone ought to compare potassium carbonate
> developers with each sulfite salt to see how big the difference is.
> Note that with cold papers, the differences resulting from these kind of
> changes is tiny, and often imperceptible.
> I don't know how difficult K2SO3 is to keep in dry form; the jar is still
> sitting on my shelf.  I don't see why it would be any harder to keep than
> the sodium version, which is ubiquitous.
> 
> 
> 
> You should be able to substitute potassium carbonate for sodium carbonate
> without concern, however, keep it tightly capped and dry, since it
> absorbs water from the air.  The molecular weights are:
> potassium carbonate               K2CO3           138.2
> sodium carbonate                  Na2CO3         106
> sodium carbonate monohydrate       Na2CO3*H2O      124
> If potassium carbonate is used rather than anhydrous sodium carbonate,
> the factor is 138.2/106 = 1.3X (1.30 g potassium carbonate used for each
> gram of anhydrous sodium carbonate required).
> If potassium carbonate is used rather than sodium carbonate monohydrate,
> the factor is 138.2/124 = 1.11X (not 0.9X).
> If sodium carbonates are substituted for potassium carbonate, the factors
> are the inverses of those given above (anhydrous, 0.77X; monohydrate,
> 0.9X).
> Both sodium and potassium carbonates give nearly the same pH, and the
> differences in development should not be evident if the correct amount is
> substituted.  Using much less carbonate than specified may warm image
> tone, but generally, developers don't affect tone very much compared
> to other factors (paper, toners, etc.).
> Benzotriazole might cool the image tone; usually, bromide (or developer
> reuse) lends a warm or greenish cast, but improves high value separation
> due to its restraining action.  Both exposure (more) and developing time
> (longer) should be adjusted if significant amounts of restrainer are used.
> Adding more carbonate to a developer to which bromide has been added or
> has accumulated, will cool the tone and decrease developing times, but
> retain high value separation.  Using the factorial timing approach
> described by Adams is convenient to adjust times after additions (10%
> solutions of KBr and Na2CO3 are convenient).
> 
> Tim
> 
> 
> 
> 
> 
> 
> On 1/25/07 4:06 AM, "C.Breukel@xxxxxxx" <C.Breukel@xxxxxxx> wrote:
> 
> >
> > }
> >>
> >> January 24, 2007, from Lloyd Erlick,
> >> regarding Ansco 120 print developer:
> >>
> >> Thus: 12 g sodium sulfite anhydrous for one liter of *working*
> > solution.
> >>
> >> The working solution I use contains 13.5 grams of potassium sulfite
> >> anhydrous. I've forgotten the arduous calculation that led to this,
> > but
> >> the
> >> solution works very nicely indeed. Maybe those more chemically adept
> > than
> >> I
> >> am can correct my numbers ...
> >
> >
> >
> > ..ok I take the "challenge"..:-)..
> >
> > molecular weight sodium sulfite: 126,04
> > molecular weight potassium sulfite: 158,26
> >
> > So 12 g sodium sulfite equels  (158,26/126,04)*12 = 1,26 * 12 = 15,12 g
> > potassium sulfite.
> >
> > A bit more than you use now, bit it ain't rocket scince, it probably
> > won't matter too much..
> >
> > Best,
> >
> > Cor
> >
> >
> >
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