Chemistry questions about DIY film developers

[Eric Woodbury]

Well, I've caught the bug. I'm tinkering with film developer recipes and there is so much chemistry I don't understand. Maybe some of the wise photo-chemists can help.

In a developer formula such as PMK, why couldn't the Metol be replaced with Phenidone or Dimezone? The pH seems fine for Phen and the skin irritation problem should be reduced.

When adding small amounts of Phenidone to TEA based developers, if I have Phen in alcohol already, is there harm in adding the Phen in alcohol to the TEA solution? Should I then boil off the alcohol once in the TEA? How bad is the fire hazard involved?

Since TEA absorbs water from the air and water can promote oxidization of some of these agents, isn't it best to heat the TEA above 212F to drive off the water? Also, I've seen some of my agents dissolved in TEA age faster in plastic bottles than in glass. Is this the oxygen permeating the plastic? Even C-TEA changes color.

How does one determine the ratios of developer agents in a multi-agent mix? Is this trial and error or is there a secret I should know?

Is there a comprehensive text on photo-chem at the local UC library?

Thanks for all the help.

[Ron Marshall]

You need a cookbook; try "The Film Developing Cookbook" by Anchell and Troop. They cover the functions of many of the basic components.

[Eric Woodbury]

Ron, I've got it. I think I want more of a chemistry book than recipes. I have many recipe books and a bunch of others, too.

[Vlad Soare]

In a developer formula such as PMK, why couldn't the Metol be replaced with Phenidone or Dimezone? The pH seems fine for Phen and the skin irritation problem should be reduced.

I believe it has to do with the difference in their activity. Metol is a strong developing agent - it could be the only developing agent in the solution and still work properly. Phenidone, on the other hand, is extremely weak by itself and only works well when combined with other agents. It works very well in combination with hydroquinone or ascorbic acid, but I don't know how well it combines with pyrogallol. This might be a reason, though I'm by no means an expert on this subject, so somebody please correct me if I'm wrong.

Anyway, metol's skin irritation problem seems irrelevant to me in this particular case, because pyrogallol alone is toxic enough. Even with metol replaced by phenidone, I still wouldn't touch the developer with my bare hand.

When adding small amounts of Phenidone to TEA based developers, if I have Phen in alcohol already, is there harm in adding the Phen in alcohol to the TEA solution? Should I then boil off the alcohol once in the TEA? How bad is the fire hazard involved?

As far as I know, alcohol is photographically inert. I would leave it alone and use it as it is.

Is this the oxygen permeating the plastic? Even C-TEA changes color.

Ordinary plastic (aka polyethylene) does indeed breathe. PET bottles should be fine, though. I have stored developers in PET bottles (squeezed to remove all air) for longer than recommended, with no ill effects.

How does one determine the ratios of developer agents in a multi-agent mix? Is this trial and error or is there a secret I should know?

A university degree in chemistry certainly helps - most reactions can be predicted with great accuracy by a trained chemist.
Those of us whose knowledge of organic chemistry is limited to vague remembrances from high school, myself included, use known developers as starting points and experiment from there.

[David Karp]

Check out the "B&W: Film, Paper, Chemistry" forum on APUG too. There are lots of interesting discussions on chemistry, usually involving Ron Mowrey and Pat Gainer. They are way over my head, not being a chemist, but probably illuminating for someone with enough background. Often, imbedded in the chemists' discussions, are practical recommendations.

[Mark Sampson]

Gordon Hutchings' "The Book of Pyro" explains his invention in great detail, along with descriptions of othe pyro-based developers. Since his introduction of PMK has revived interst in Pyro developers, other people have invented their own, most notably Sandy King's Pyrocat-HD.

[paulr]

A university degree in chemistry certainly helps - most reactions can be predicted with great accuracy by a trained chemist.
Those of us whose knowledge of organic chemistry is limited to vague remembrances from high school, myself included, use known developers as starting points and experiment from there.

I think in order to truly formulate a developer scientifically, you'd need much more than a degree in chemistry ... you'd need to have done your PhD research on the topic. The relationships between developer ingredients and real world results on particular films would be an arcane and specific field of study.

I think most developers get formulated the way you said ... using known developers as a starting point and working empirically.

To forumulate a developer, you work less like an analytical chemist than like a pastry chef. You study existing recipes. You do research ... you learn that certain ingredients work with each other in certain ways; that changing propportions in one direction or another pushes certain qualities around predictably. More or less.

And you experiment ... one variable at a time if you're clever. And you test your results by profoundly unscientific means ... like looking at photos of rocks, or eating cake. And eventually you get something that you stick with.

I've created film developers and ice cream recipes ... the process is identical.

[Keith Tapscott.]

Well, I've caught the bug. I'm tinkering with film developer recipes and there is so much chemistry I don't understand. Maybe some of the wise photo-chemists can help.

In a developer formula such as PMK, why couldn't the Metol be replaced with Phenidone or Dimezone? The pH seems fine for Phen and the skin irritation problem should be reduced.
Is there a comprehensive text on photo-chem at the local UC library?

Thanks for all the help.

Metol is an excellent reducing agents and the so called Metol poisoning usually came from the less pure sources. Metol is also easier to weigh than Phenidone and it`s derivatives. Don`t sprinkle it on your breakfast cereal or drink the developer.

I have recently started making my own B&W developers, although I continue to buy stop-baths, fixers and other sundries. I make the basic D-76 film developer, but only when needed and the volume required. Sometimes, I make just half a litre of stock. That way, I don`t have excess unused stock solution turning bad on the shelf. I use the developer well within a week of mixing it and I am pleased with the results. I use it diluted 1+1.

[Vlad Soare]

Metol is an excellent reducing agent
[...]
Metol is also easier to weigh than Phenidone and it`s derivatives.

I agree. I also think that the advantages of phenidone over metol are highly overrated, while its disadvantages seem to go unnoticed.
I personally find phenidone to be a nuisance. Firstly, dissolving it in water is a frustrating - and often unsuccessful - experience. Secondly, it goes bad very quickly even when stored as a powder (unlike metol, which keeps for decades). Thirdly, it's difficult to weigh accurately. It's more expensive than metol, too.
I strongly believe in the old adage "if it ain't broke, don't fix it". Metol is cheap, keeps for ages, has been working perfectly for more than a century, and is very easy to work with (easy to weigh, easy to dissolve). It works; why fix it? Why replace it with something expensive (admittedly not by much) and capricious whose sole advantage is that it doesn't irritate skin? It's extremely easy to use metol without irritations: either don't touch it, or wear gloves. I do both.

[IanG]

The Metol can be replaced by Phenidone, Ilford did this with many of their developers, and more recently some use Dimezone in stead of Phenidone.

The Phenidone is far more active than Metol and you only need to use around 10-12% of the equivalent amount of Metol. ID-4 which is a Metol-Pyrogallol developer has 4 gms Metol, the Phenidone-Metol equivalent uses 0.4 gms Phenidone.

The Pyrogallol is worse for your skin than Metl

C I Jacobson & R Jacobson, Developing, Focal Press, is an excellent book & can be found second-hand, but get a later edition 9th onwards (1973).

Phenidone developers have many advantages, particularly print developers as they have better shelf & tray life as well as better throughput. Also much easier to make more concentrated developers with Phenidone.

Ian