Pyrocat HD with Sodium Sulfite

Donald Miller · Apr 8, 2006

Awhile back I made the error of compounding the A portion of Pyrocat with sodium sulfite rather then sodium metabisulfite. The result is a more active developer with what appears to be similar B+F (not densitometrically determined).

I mixed this using equal amounts of sodium sulfite for what the formula calls out for metabisulfite.

If anyone is so inclined they may want to check this out further. I don't have the interest nor the time. However, I will probably continue using the sodium sulfite version in the future.

Jim Noel · Apr 8, 2006

This is interesting to me. I hope one of our more knowledgeable participants will chime in.

sanking · Apr 8, 2006

Jim Noel said:
This is interesting to me. I hope one of our more knowledgeable participants will chime in.

Well, I have a couple of comments.

First, we use sodium metabisulfite in the stock solution as a preservative. When you mix the working solution sulfite ions are released, so the function is the same. The ratio of substitution is, I belive about 13:10, in other words, 13 grams of sodium sulfite replaces 10 grams of metabisulfite.
But remember, if you were to use soidum sulfite instead of metabisulfite in the stock solution that will decrease its shell life.

OK, just on sulfite in the working formula. Pyrocatechin is very sensitive to both sufite and ascorbic and both function as a very strong restrainer and they also add just a bit of synergism. As you increae the amount of either sulfite or ascorbic to the formula several things happen: 1) Restraining action is greater so effective film speed is decreased, 2) B+F in the UV is decreased, and 3) the intensity of the stain is decreased. And if you add enough of either sulfite or ascorbic, you will eliminate the stain altogether.

Sandy

Donald Miller · Apr 8, 2006

sanking said:
Well, I have a couple of comments.

First, we use sodium metabisulfite in the stock solution as a preservative. When you mix the working solution sulfite ions are released, so the function is the same. The ratio of substitution is, I belive about 13:10, in other words, 13 grams of sodium sulfite replaces 10 grams of metabisulfite.
But remember, if you were to use soidum sulfite instead of metabisulfite in the stock solution that will decrease its shell life.

OK, just on sulfite in the working formula. Pyrocatechin is very sensitive to both sufite and ascorbic and both function as a very strong restrainer and they also add just a bit of synergism. As you increae the amount of either sulfite or ascorbic to the formula several things happen: 1) Restraining action is greater so effective film speed is decreased, 2) B+F in the UV is decreased, and 3) the intensity of the stain is decreased. And if you add enough of either sulfite or ascorbic, you will eliminate the stain altogether.

Sandy

Sandy,

From what you say, I effectively decreased the amout of sulfite because in erroneously mixing the formula with sodium sulfite I used the same quantities that you specifiy for metabisulfite.

While I have not determined the densities of the negatives, judging by the appearance of the negatives developed in sodium sulfite, they are developed to a higher density range for the same development time and solution strength.

Again visually judging the negatives, the b + f appears to be comparable. Since I use the mixed developer within a period of weeks rather then months I care only about it having a shelf life sufficient to last through my normal usage cycle.

As I mentioned at the outset, I like the negatives that result from the Sodium Sulfite mixture more then I do those from the Metabisulfite mixture. For that reason I am not going to do any more testing on my end. I am all about making photographs and not about testing developer formulations.

sanking · Apr 8, 2006

Donald Miller said:
Sandy,

From what you say, I effectively decreased the amout of sulfite because in erroneously mixing the formula with sodium sulfite I used the same quantities that you specifiy for metabisulfite.

While I have not determined the densities of the negatives, judging by the appearance of the negatives developed in sodium sulfite, they are developed to a higher density range for the same development time and solution strength.

Again visually judging the negatives, the b + f appears to be comparable. Since I use the mixed developer within a period of weeks rather then months I care only about it having a shelf life sufficient to last through my normal usage cycle.

As I mentioned at the outset, I like the negatives that result from the Sodium Sulfite mixture more then I do those from the Metabisulfite mixture. For that reason I am not going to do any more testing on my end. I am all about making photographs and not about testing developer formulations.

Hi Donald,

Yes, I think you must have decreaed the amount of sulfite. You probably would not see any difference in B+F, or be able to measure any with a densitometer in Visual or Blue mode, but there would be a significant increase if measured in UV. And decreasing B+F in the UV is one of the most important considerations in my testing of formulas since too much B+F stain will make long exposures unbearable.

Sandy

dancqu · Apr 9, 2006

Donald Miller said:
Awhile back I made the error of compounding the A
portion of Pyrocat with sodium sulfite rather then sodium
metabisulfite. The result is a more active developer with
what appears to be similar B+F ...

I mixed this using equal amounts of sodium sulfite for what
the formula calls out for metabisulfite.

If anyone is so inclined they may want to check this out
further. I don't have the interest nor the time. However,
I will probably continue using the sodium sulfite version

I'm one to puzzle over such matters. The exact ratio is
190:252; 190 grams of the meta equals 252 grams of the
sulfite for SO3. So the sulfite level is reduced.

Both your self and Sandy have overlooked the ph of the
A solution. For longevity acid solutions can be much better.
Also, as with phenidone, solubility is a consideration. But
that's another matter. Your A has less sulfite. Likely it's
ph is much higher and very alkaline by comparison. Dan

Donald Miller · Apr 9, 2006

Dan, Those are my thoughts and questions as well. I attribute the consistantly higher DR with the Sulfite mixture then with the Metabisulfite mixture to higher ph...but then I may be wrong. I am not a chemist. I will continue working with what has worked for me.

sanking · Apr 10, 2006

Donald Miller said:
Dan, Those are my thoughts and questions as well. I attribute the consistantly higher DR with the Sulfite mixture then with the Metabisulfite mixture to higher ph...but then I may be wrong. I am not a chemist. I will continue working with what has worked for me.

As for pH, metabisulfite makes the stock solution acidic, and that helps to preserve it. However, the pH of the working solution will not be changed very much, if at all, by substituting sulfite, or bisulfite or metabisulfite, since the carbonate gives very good buffering at the percentage used in the formula. Still, pyrocatechin is very sensitive to sulfite, so a change from 13 sulfite ons to 10 would be sufficient to explain a small change in working characteristics.

Sandy

dancqu · Apr 10, 2006

sanking said:
...the pH of the working solution will not be
changed very much, if at all, by substituting sulfite, ...
Still, pyrocatechin is very sensitive to sulfite, so a
change from 13 sulfite ons to 10 would be sufficient
to explain a small change in working characteristics.
Sandy

I'll have to agree. I had no idea this developer's
working strength solution is so loaded with carbonate.
My computation of the sulfite ion ratios twixt the metabisulfite
and sulfite of sodium is 9.8 to 13. So, for sulfite ion
equivalence add 1/3 more of the sulfite.

Pyrocatechin I'd guess quite acidic. If so, the 1/5th
portion of sodium sulfite added by Donald likely left the
A solution at less than ph 7. Is all that carbonate needed?
With so little of other ingredients near max ph should
be reached with 2, 3, 4 grams per liter
working strength. Dan

sanking · Apr 10, 2006

dancqu said:
I'll have to agree. I had no idea this developer's
working strength solution is so loaded with carbonate.
My computation of the sulfite ion ratios twixt the metabisulfite
and sulfite of sodium is 9.8 to 13. So, for sulfite ion
equivalence add 1/3 more of the sulfite.

Pyrocatechin I'd guess quite acidic. If so, the 1/5th
portion of sodium sulfite added by Donald likely left the
A solution at less than ph 7. Is all that carbonate needed?
With so little of other ingredients near max ph should
be reached with 2, 3, 4 grams per liter
working strength. Dan

Pyrocatechin requires a very high working pH. The high carbonate content allows good buffering of the working solution with a wide range of dilutions from 1:1:100 to up to 1:1:400, and many people are using Pyrocat with the very dilute solutions for stand and semi-stand development.

Also, theory of carbonate acutance developers is that a small amount reducer plus high amount of carbonate gives more acutance than more reducer and less carbonae. There is a trade-off here that I arrived at empirically in testing.

Sandy

Pyrocat HD with Sodium Sulfite

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