D-76, pH elevation with storage

lensmagic · Dec 20, 2009

Bill Troop, in The Film Development Cookbook (p. 42), describes how, upon storage over a few months, the pH of D-76 can rise from 8.3 to 9.0. What chemical reaction is at work here? Which chemicals (ingredients) are involved in producing the rise in pH?

MikeSeb · Dec 20, 2009

Hydroquinone, I think. As I recall, solving this problem was the genesis of D-76H, which differs from D-76 by having slightly more metol per liter (2.5 g vs 2.0), and by omitting the hydroquinone. I've used both; they are pretty much identical, and the -H version is said to remain pH stable in storage.

I tend to mix small quantities and use it up pretty fast, so I've never really been able to test this assertion for myself.

john_s · Dec 21, 2009

You might find this page by Ryuji Suzuki interesting:

Dead Link Removed

Note that some tables are not showing properly. Some detective work is necessary where two formulas are strung into a single line.

brucemuir · Dec 21, 2009

What would the consequences be from the elevated PH?

I also though that Kodak had adjusted the packaged D 76 so this is no longer a problem ? ? ?

Photo Engineer · Dec 21, 2009

HQ reacts with Oxygen giving Quinone which reacts with Sodium Sulfite giving HQ-Mono Sulfonate and Hydroxide ion which causes the pH to rise slightly. The explanation here is perhaps an oversimplification, but is for you non-chemists. Mees, Mees and James and Haist all discuss this with chemical symbols and the whole detailed agonizing organic chemistry stuff.

This change though, causes a very tiny increase in activity due to the rise in pH but the loss in HQ is what prevents it from being a huge change. Also, the Oxygen dissolved in the water is used up. In the long run, the developer stabilzes and everything is OK. Usually, I let my D-76 sit for 24 hours before use and this damps out the problem.

There are errors on the web site referenced above, so beware as it is hard for one to separate the wheat from the chaff there. This has been commented on here before by other APUG members.

PE

Arvee · Dec 21, 2009

brucemuir said:
What would the consequences be from the elevated PH?

I also though that Kodak had adjusted the packaged D 76 so this is no longer a problem ? ? ?

Higher contrast for equivalent development times.

Kodak made changes to mitigate this problem.

-F.

Keith Tapscott. · Dec 22, 2009

Photo Engineer said:
HQ reacts with Oxygen giving Quinone which reacts with Sodium Sulfite giving HQ-Mono Sulfonate and Hydroxide ion which causes the pH to rise slightly. The explanation here is perhaps an oversimplification, but is for you non-chemists. Mees, Mees and James and Haist all discuss this with chemical symbols and the whole detailed agonizing organic chemistry stuff.

This change though, causes a very tiny increase in activity due to the rise in pH but the loss in HQ is what prevents it from being a huge change. Also, the Oxygen dissolved in the water is used up. In the long run, the developer stabilzes and everything is OK. Usually, I let my D-76 sit for 24 hours before use and this damps out the problem.

There are errors on the web site referenced above, so beware as it is hard for one to separate the wheat from the chaff there. This has been commented on here before by other APUG members.

PE

I mix the standard D-76/ID-11 formula and do the same as you, by waiting a day or two before use. People forget that D-76 was originally formulated to be reused and replenished. When a few rolls have been processed in a litre of stock solution, it actually reduces in activity and requires replenishment.
I think that diluting D-76 and ID-11 was first recommended when the then new thin emulsion, high definition films started to appear.

lensmagic · Dec 22, 2009

HQ reacts with Oxygen giving Quinone which reacts with Sodium Sulfite giving HQ-Mono Sulfonate and Hydroxide ion which causes the pH to rise slightly.

PE, your response, stated as it is with crystal clarity, is just what I was looking for. Thank you.

RalphLambrecht · Dec 22, 2009

Photo Engineer said:
HQ reacts with Oxygen giving Quinone which reacts with Sodium Sulfite giving HQ-Mono Sulfonate and Hydroxide ion which causes the pH to rise slightly. The explanation here is perhaps an oversimplification, but is for you non-chemists. Mees, Mees and James and Haist all discuss this with chemical symbols and the whole detailed agonizing organic chemistry stuff.

This change though, causes a very tiny increase in activity due to the rise in pH but the loss in HQ is what prevents it from being a huge change. Also, the Oxygen dissolved in the water is used up. In the long run, the developer stabilzes and everything is OK. Usually, I let my D-76 sit for 24 hours before use and this damps out the problem.

There are errors on the web site referenced above, so beware as it is hard for one to separate the wheat from the chaff there. This has been commented on here before by other APUG members.

PE

PE

There must be more to the story. How about the long term effect? I've seen D76 to rise in activity for months, and it is not a minute change. This was a published test, but I forgot where I've seen it. Also, is it really activated by oxygen? If that's true, then storing D76 stock solution in glass containers without air (I use olive glasses and only leave a tiny air bubble) should prevent the long-term effect. What do you think?

In the meantime, must read Mees again.

Ian Grant · Dec 22, 2009

I've seen those tests Ralph, like you I can't remember the site but the methodology was very flawed and there were some rather anomalous results. I think the comparison of D76 was against others including a PQ developer of the authors own concoction.

As has been commented D76 was not designed for one shot or dilution, it was a motion picture developer which happens to be good enough to be used those ways and it has become the De Facto standard.

When used replenished it does eventually collapse, usually due to high a bromide level, where as there are PQ developers that can be replenished almost ad-infinitum.

Kodak spent many tears tinkering with D76 and it's variants of which there are reportedly over 30 official Kodak variations which have been published in Research papers. Eventually Xtol was released which overcame many of D76's problems.

Ian

Photo Engineer · Dec 22, 2009

Ralph;

Oxidation goes on until the developer becomes inactive. So if you use a glass bottle, the Oxygen is essentially used up, but in plastic, the porosity allows inward diffusion. Also, it is more complex than this simple descriptoin.

Try Mees or Haist. They do it in gory detail.

PE

Keith Tapscott. · Dec 22, 2009

RalphLambrecht said:
PE

There must be more to the story. How about the long term effect? I've seen D76 to rise in activity for months, and it is not a minute change. This was a published test, but I forgot where I've seen it. Also, is it really activated by oxygen? If that's true, then storing D76 stock solution in glass containers without air (I use olive glasses and only leave a tiny air bubble) should prevent the long-term effect. What do you think?

In the meantime, must read Mees again.

I use glass medicine bottles with child-proof screw on caps which I fill to the brim. No problems to report so far.

lensmagic · Dec 22, 2009

I am getting a little off-topic now, but does anyone know if Nalgene "bottles" are as good as glass in blocking gas?? Or, as I could have phrased it: Are Nalgene bottles the same as plastic bottles in passing gas??

Photo Engineer · Dec 22, 2009

Nothing is as good as glass. Then, plastics come after graded according to type posted here before in similar threads.

PE

Rick Jones · Dec 23, 2009

lensmagic - I can only answer your questions based on my personal experience using 1 liter Nalgene (thick body) bottles over the last 25 years. I had read so much about problems with both aging D76 and gas permeable plastics that I simply had to find out first hand by shooting two identical rolls and processing one in D76 purposely aged for 9 months and the second in a freshly mixed batch. D76 stored for 9 months showed only the slightest increase in activity. That is, the film processed in the aged developer produced slightly more contrast. I estimated the increase amounted to about +3/4 grade increase. Not very scientific but enough to convince me my Nalgene storage system worked for me and that D76 aging would not be a problem in my use.

D-76, pH elevation with storage

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