E-72C update

[Maine-iac]

Back in January, I reported (see Chemistry recipes) that I had mixed up a Phenidone/Vitamin C variant of E-72 in a 3X concentration, but leaving out the alkaline activator (carbonate). I theorized that by leaving out the activator, it might make for long keeping properties.

My hunch was right. Yesterday, I used up the rest of the concentrate that I had mixed more than ten months ago. Diluted 1:9 and with the carbonate added directly to the tray where it dissolves very quickly, it was as active as when I first mixed it up. The concentrate was hardly even discolored-- perhaps a tad darker shade of brownish-yellow, but nothing to write home about.

This formula also has great keeping properties after being mixed up. I once left a partially-used batch sit in the tray for five days before coming back to test it. While it had darkened a bit in the interim, it still worked just fine and I ran quite a few more prints through it.

E-72 is essentially a Dektol-like developer but in my variation, without hydroquinone and using Edwal Liquid Orthazite instead of bromide.

I like it a lot.

Larry

P.S. Found an old (3-4 years) 25 sheet pack of Ilford MGFB IV. It's fogged--weak blacks. Any hope of salvaging it?

 

[Jennifer]

Hi,
This is very interesting. It layed in the tray and still was ok. No "sudden death" vit-c like in xtrol. There is also a E-76 version, for replacing D-76.
Wonder if it has same qualities ?.

Jennifer

 

[srs5694]

Maine-iac's stock solution was missing the activator, which would have the effect of lengthening its keeping qualities. Leaving it in a tray for five days is certainly a bit of a "torture test," but that's a separate question from its long-term storage when missing the activator. Also, it's important to know if it was covered by Saran Wrap or something during the 5-day tray test; if so, the results, although good, are much less impressive than if it had been exposed to air for that time. Certainly ordinary E-72 is likely to last much longer than 5 days if kept in a sealed bottle, and I'd expect a well-"sealed" tray to do as well. (Although expelling the air and "sealing" the tray would be harder than doing the equivalent with a bottle.)

You could certainly make a split-stock version of E-76. In fact, if you go down that path it might just lead you to something very much like PC-Glycol, which is a phenidone/ascorbic acid developer with claimed excellent long-term keeping qualities because of its split-stock nature and the fact that the phenidone and vitamin C are kept in propylene glycol rather than water (until just before mixing). With an appropriate "B" bath, you'll get something that's nearly identical to E-76.

 

[gainer]

There is really not much point in making a stock solution of anything but the phenidone, which if dissolved in propylene glycol or glycerine will last a long time. The ascorbic acid, or its isomer erythorbic acid, is very quickly dissolved in plain water, as is the carbonate. If you find that you need sulfite, it too is readilly dissolved in the working solution. I don't think sulfite adds much to the tray life, but it may have other effects. When it comes to aerial oxidation, the ascorbic acid is more likely to protect the sulfite according to what I have read, forming dehydroascorbic acid.
Teaspoon formulas work quite well for print developers.

Ryuji Suzuki's research shows that iron in the water, which is often present even in the distilled water that you buy, is the main cause of premature death of ascorbate developers, and that salysilic acid is the cure. Perhaps you should add a little bit of an extract of willow bark. My father told me that when he was young, the home cure for headache was to chew willow twigs.

 

[Alan Johnson]

When I mixed sodium ascorbate and phenidone in solution as part A of a two bath developer it went off after about 4 months in a full stoppered glass bottle and gave thin negs. Larry seems to have shown experimentally that one way to preserve ascorbate-phenidone is to keep it acidic.

 

[dancqu]

Larry seems to have shown experimentally that one way
to preserve ascorbate-phenidone is to keep it acidic.

Shown? Confirmed is correct as it is recognized that chemicals
oxidize less so in acidic solutions. There are many two part, A-B,
developers. Dan

 

[Alan Johnson]

Yes Dan. I believe you have previously suggested sodium metabisulfite as a possible ascorbate preservative and Larry's work suggests it might be worth a try added to sodium ascorbate and phenidone as a Vit-C part A two bath developer.

 

[Jordan]

Yes Dan. I believe you have previously suggested sodium metabisulfite as a possible ascorbate preservative and Larry's work suggests it might be worth a try added to sodium ascorbate and phenidone as a Vit-C part A two bath developer.

A simpler solution might be to use an equimolar amount of ascorbic acid instead of sodium ascorbate and adjust the B part of the two-bath developer accordingly (so that the final working solution is at the correct pH).

Aqueous solutions of ascorbic acid and phenidone have a decently long shelf life.

 

[dancqu]

A simpler solution might be to use an equimolar
amount of ascorbic acid

Aqueous solutions of ascorbic acid and phenidone
have a decently long shelf life.

That is what Larry did. That is what he had, a solution
of the two agents three times the usual stock strength.
At least that is how I read his post. Seems reasonable
to the both of us. Dan

 

[Gerald Koch]

Back in January, I reported (see Chemistry recipes) that I had mixed up a Phenidone/Vitamin C variant of E-72 in a 3X concentration, but leaving out the alkaline activator (carbonate). I theorized that by leaving out the activator, it might make for long keeping properties.

While reducing the pH will reduce the rate of ordinary oxidation of ascorbate developers it has no effect on the Fenton reaction which is given as the cause of the sudden death syndrome. The Fenton reaction is catalysed by Iron (III) and/or Cu (II) in the developer solution. Iron contamination is common for certain developer chemicals like sodium sulfite and some water supplies.

Ascorbate developers are most stable at a pH of 5.4.

 

[Ryuji]

I don't think sulfite adds much to the tray life, but it may have other effects.

Not true. Sulfite makes a big difference in the tray life of well formulated developers.

When it comes to aerial oxidation, the ascorbic acid is more likely to protect the sulfite according to what I have read, forming dehydroascorbic acid.

Not true. Sulfite can be used to prolong the tray life of the developer significantly. Note that I am not saying adding sulfite will prolong the tray life. Adding sulfite to unstabilized ascorbate developers doesn't buy you the same thing as adding it to already stabilized solution.

Ryuji Suzuki's research shows that iron in the water, which is often present even in the distilled water that you buy, is the main cause of premature death of ascorbate developers, and that salysilic acid is the cure.

I never showed such a thing. The water theory is a bastardized cut-and-paste postings you see on teh net and that is not what I proposed to be the significant reason for the short life of most ascorbate-based developers.

Furthermore, salicylic acid may be an effective agent to improve this aspect, when used alone, it is pH-dependent and I find it necessary to use other tricks in order to make ascorbate developers that are more robust than experimental formulae that are found on the web.

 

[Ryuji]

Aqueous solutions of ascorbic acid and phenidone have a decently long shelf life.

It depends on how. Acidic solution of ascorbic acid in absence of suitable stabilizing additives may die very fast without discoloration, generating peroxide.

 

[Maine-iac]

That is what Larry did. That is what he had, a solution
of the two agents three times the usual stock strength.
At least that is how I read his post. Seems reasonable
to the both of us. Dan

Right! I use ascorbic acid, not sodium ascorbate. My local health food store carries a very good grade of Vitamin C crystals that are almost pure ascorbic acid. Cheaper than the Formulary and perfect in performance in my developers.

Also, in the open tray "torture test" I did not cover the tray with saran wrap or anything else. My darkroom session got interrupted after having run only 4-5 prints through the tray, so I decided to just leave it there to see how long it would last. Five days later, it was quite discolored, but still energetic. I only ran another 8-10 prints through it in that session, so it didn't get a real test to see if its total capacity had been diminished by all that tray time. I suspect it did, but I didn't push it that far.

Larry

 

[Maine-iac]

While reducing the pH will reduce the rate of ordinary oxidation of ascorbate developers it has no effect on the Fenton reaction which is given as the cause of the sudden death syndrome. The Fenton reaction is catalysed by Iron (III) and/or Cu (II) in the developer solution. Iron contamination is common for certain developer chemicals like sodium sulfite and some water supplies.

Ascorbate developers are most stable at a pH of 5.4.

No argument with what you said, Gerald. Just want to make clear that whatever I write in this forum about Phenidone/Vitamin C developers is based on the use of Ascorbic Acid rather than on Sodium Ascorbate. I have never used Ascorbate, nor am I likely to. As you well know, the two are not the same, and they behave somewhat differently in formulas. I've found (this thread is evidence) that in discussions, there is frequently a tendency to confuse the two, and I just wanted to make clear which one I'm using and talking about. I've been using Vitmain C (ascorbic acid) crystals or powder (occasionally even with Rose Hips) in my formulas for years with no adverse effects. I do make sure, as Gainer warns, that the label doesn't say dihydroascorbic acid.

Larry

 

[Gerald Koch]

Hi Larry,

I get sodium erythorbate from Sutton Bay Trading company for $6.33 a pound. Since the acid is already neutralized I find it easier to use than ascorbic acid.