Diluting divided developer?
I'm finding dev times with Formulary divided D-76 to be very short, essentially uncontrollable, if low contrast negs are needed.
Developing in bath A only shows some activity so would it be possible to dilute bath A and get back to longer bath B times or maybe titrate the pH down a bit with sodium metabisulfite to achieve the same effect?
Thought I'd ask the assembled expertise before I muck up the only batch sitting on the shelf at the moment. TIA.
"I'm finding dev times with Formulary divided D-76 to be very
short, essentially uncontrollable, if low contrast negs are needed."
Hardly the results one needs from a divided developer. What film?
"Developing in bath A only shows some activity so would it be
possible to dilute bath A and get back to longer bath B times or
maybe titrate the pH down a bit with sodium metabisulfite to
achieve the same effect?"
I'd consider substituting a one-shot bicarbonated B for the
current B. Perhaps a heaping teaspoon each 500ml.
I would not dilute the A bath. Your B bath is too active;
building contrast too quickly. Your film? Dan
Pete, what times are you using?
Pete, I'd call the Formulary and ask them how to decrease contrast.
Formulary Divided D-76 Film Developer
Distilled Water 52⁰C – 125⁰F 750ml
Borax 60 grams
Cold Water to make 1000ml
“the pH (of a Borax solution) varies very little with borax solution concentration.”
I assume that addition of Boric Acid would buffer the solution and reduce the solution pH.
I expect that adding Sodium Metaborate would raise the solution pH.
Everything is analog - even digital :D
I need hardly remind you fellows that concentration affects action even if pH is constant. In the early days of pushing, some like Vestal and Schwalberg were saturating the borax in D-76. Now, I suppose what really happened was that although the pH one would measure may not have changed much, the concentration caused the local rate of change of pH also not to change much. In the present case, it may be that reducing the concentration of borax may allow the local pH to decrease. even though before and after measurements may show no change.
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Originally Posted by dancqu
The Formulary bath B is a 6% (by weight) solution of Borax which was made with distilled water after heating to ~52C. Half the bottles have a hard precipitate in the bottom which I assume to be that which couldn't be held in solution at room temp but keeps the pH constant in solution by keeping the concentration at or near saturation.
I could titrate the pH of the borax solution downward with some boric acid which would reduce the concentration of tetraborate hydroxide but the buffering action of the solution would hold pH regardless.
I've mixed up some 5% by weight sodium carbonate bath B as well as some 5% sodium metaborate bath B but they both have a higher pH although neither is anywhere near saturation (I think). I have sodium bicarbonate to titrate the former down in pH and again, boric acid, for the latter. But the concentrations won't change.
Maybe just diluting the borax solution is the way to go?
I started with 3min in bath A with agitation for the first 30sec and five inversions over 10s at each 30sec mark for all films.
Originally Posted by jim appleyard
For 200ISO and below I started with 3min in bath B with the same agitation (initial tries at letting it stand generated a lot of bromide streaking) and at 2min with the same agitation.
With 400ISO I started with 4min, and then 3min, in bath B with the same agitation.
In all cases, with the exception of 400TX at an EI of 250, the density was way too high to make the slightest use of. The 400TX calculates out to a -42% dev for a CI of 0.42, or about 2min, 20sec - a might touchy.
I emailed earlier about diluting bath A, as well as adding sodium metabisulfite to reduce the pH of bath A, but didn't ask the obvious question - how to reduce contrast. Thanks for that.
Originally Posted by Tom Hoskinson
And that's the document I have on file and the formulation for the bath B I've been using.
OK, thanks, that makes sense. What isn't obvious to a non-chemist like me is what concentration yields a local hydroxyl concentration drop at the surface of the film that under equilibrium conditions during development allows for an extended time to achieve the desired contrast.
Originally Posted by gainer
I suppose I could dilute the saturated solution by half each time until a reasonable time is reached. Looking through H. T. James' tome the answer is far from obvious and I've no clue where to start in making an attempt at calculating a better starting concentration.
Shot and dev'ed eight more rolls, two of each. Oddly, all exhibit development artifacts no different from the previous non-divided developed films. Go figure. Now if I could just remember what it was I was doing before...
After a few iterations it looks like 60ml of 6% borax solution plus enough distilled water to make 1000ml yields acceptable times and densities for all ISOs under test.
One thing I forgot to mention is the film is dried in a DSA/Senrac dryer under heat for about five to eight minutes and then the balance with the heater off. The last roll processed I deliberately put in upside down and whaddayaknow the 'surge' patterns appeared on the top edge which indicates the moving air may be partially responsible. Gonna have to test this more carefully I think.
Thanks to everyone for all the help, it's much appreciated believe me.