slowing down HC-110 development

[Rudeofus]

You are correct, there is also some Catechol in HC-110. I have no idea why it would be in there at all, and given that it is present in much lower amount than Hydroquinone, I doubt that different pH will change its effect.

 

[Raghu Kuvempunagar]

This may be true, but there are only few developer formulas out there with competing development agents, and HC-110 is not one of them. AFAIK HC-110 uses Dimezone-S and Hydroquinone, these are superadditive but not competing.

Reducers apart, a typical developer also has solvents which in the case of HC-110 could be Sodium Sulphite and Diethanalomine. The activity of solvents is a determining factor as far as grain is concerned. Now, would the solvents be as active in low pH working solution as they are in regular working solution? Apologies again if this is a naive question.

 

[Photo Engineer]

HQ and PD are certainly not competing, but as for superadditivity, this is an open question. There is evidence for this, but there are other possible explanations.

PE

 

[Saganich]

Benzotriazole. I've used this as a development restrainer for pulling very overexposed negatives and keeping normal development times. I've not tried it on Hc110 but only D23 and Fx family. Not sure how it would work on normally exposed negatives; if more development time would increase density.

 

[Rudeofus]

Reducers apart, a typical developer also has solvents which in the case of HC-110 could be Sodium Sulphite and Diethanalomine. The activity of solvents is a determining factor as far as grain is concerned. Now, would the solvents be as active in low pH working solution as they are in regular working solution? Apologies again if this is a naive question.

pKa of Ethanolamine (that's the active solvent, no so much the Diethanolamine) is 9.5, which means that at pH < 9 almost all of it will be protonated. Therefore I would not expect much of a difference between pH 8.9 and whatever the Acetic Acid spiked version ends up at.

@Saganich : If you add more and more Benzotriazole, development will be slower, but shadow regions will be affected most. You'd likely lose film speed that way.

@Photo Engineer : the question was whether Catechol and Hydroquinone would compete for oxidized Dimezone-S, and whether the ratio of activity between these two would significantly shift as pH is lowered. Question is also whether it matters given the high ratio of Hydroquinone to Catechol amounts.

 

[Photo Engineer]

Rudi, of course. I did not address the Catechol issue because frankly, I don't know enough about the chemistry of Catechol nor its interactions with the other developing agents.

Sorry.

PE

 

[Raghu Kuvempunagar]

the question was whether Catechol and Hydroquinone would compete for oxidized Dimezone-S, and whether the ratio of activity between these two would significantly shift as pH is lowered. Question is also whether it matters given the high ratio of Hydroquinone to Catechol amounts.

Rudy and PE: Is it proven beyond doubt that Catechol is super-additive with Phenidone or Dimezone? I remember Jay Defehr, as someone who has a fair bit of experience with Catechol developers, expressing his skepticism about Catechol's super-additivity with Phenidone. See
https://www.largeformatphotography....sidian-Aqua-catechol-staining-developer/page3.

 

[Rudeofus]

Jay de Fehr refers to two carbonate based developers running at high pH values (Sandy King lists pH 10.9 for Pyrocat HD). Catechol will be plenty active on its own at this pH and may not much benefit from Phenidone, but things are likely different at the pH of HC-110.

 

[Raghu Kuvempunagar]

Jay de Fehr refers to two carbonate based developers running at high pH values (Sandy King lists pH 10.9 for Pyrocat HD). Catechol will be plenty active on its own at this pH and may not much benefit from Phenidone, but things are likely different at the pH of HC-110.

pH of HC-110 working solution is supposed to be around 9.0. If Catechol is super-additive with Phenidone/Dimezone at this pH then it should be easy to verify this experimentally and decades of developer research must have already done this and come to a conclusion about it. Am I missing something?

And is there a Catechol-Phenidone developer that is known to work well at pH 9 or lower?

 

[Rudeofus]

pH of HC-110 working solution is supposed to be around 9.0. If Catechol is super-additive with Phenidone/Dimezone at this pH then it should be easy to verify this experimentally and decades of developer research must have already done this and come to a conclusion about it. Am I missing something

Whatever these decades of developer research brought up, it never went public. Catechol was used for two of its properties: some compound formed with PPD (Meritol, MCM-100, ...) and its staining properties. In both cases Phenidone offered no improvement it seems.

And is there a Catechol-Phenidone developer that is known to work well at pH 9 or lower?

I checked through various formula books and found nothing. In fact I did not even find a Metol-Catechol low pH developer. This doesn't mean much, others might find something ...

 

[Photo Engineer]

I have no idea what Catechol is used for. I suppose it is the secret ingredient present to confuse everyone.



PE

 

[MattKing]

I have no idea what Catechol is used for. I suppose it is the secret ingredient present to confuse everyone.



PE

Is it magenta?

 

[Photo Engineer]

Not a colorful answer!

 

[Murray Kelly]

Alan, to slow down a developer nobody has suggested sugar. Or Na2SO4. I even used methyl cellulose for fun.
Thanks for the pH of Hc-110; I made it a bit lower (8.8) with my fishtank meter.
1ml rodinal + 1ml HC-110 in 250 ml for a stand development is a good combo for contrasty document films altho that is not your problem. But, I noted the HC-110 swamped the pH of the rodinal big time. Not a budge. It has a very good buffering system. c.f. FX-55 with its dual system.

 

[alanrockwood]

Alan, to slow down a developer nobody has suggested sugar. Or Na2SO4. I even used methyl cellulose for fun.
Thanks for the pH of Hc-110; I made it a bit lower (8.8) with my fishtank meter.
1ml rodinal + 1ml HC-110 in 250 ml for a stand development is a good combo for contrasty document films altho that is not your problem. But, I noted the HC-110 swamped the pH of the rodinal big time. Not a budge. It has a very good buffering system. c.f. FX-55 with its dual system.

Interesting. I have wondered about whether mixing of HC110 and Rodinal could be useful.

 

[alanrockwood]

I have no idea what Catechol is used for. I suppose it is the secret ingredient present to confuse everyone.



PE

I don't know either, but I will take a wild guess that catechol, which is an isomer of hydroquinone, might be present as an impurity in hydroquinone synthesis.

By the way, I have been looking at the MSDS sheet for HC110, and I think I can make a reasonable guess at the functions of most of the chemicals listed in the MSDS. Of course, there may be some compounds present in very low concentrations that are not listed, and some of them may have functional utility.

I also compared the MSDS of HC110 to the MSDS of L110, and there are some pretty large differences in the chemistry. Therefore, although L110 is often called a direct substitute of HC110, that might not be true under all conditions.

 

[Fujicaman1957]

Photo Engineer-

Somewhat off topic....Would you happen to know when HC-110 was introduced? I can't find any info on that.

 

[Photo Engineer]

I have no information on the introduction date of HC110.

I do know that the formula is constructed such that no water is needed to prepare the concentrate. This allows for long keeping.

As for catechol being an impurity found in HQ, that is possible. It depends on how the HQ is made I suppose.

PE

 

[MattKing]

Photo Engineer-

Somewhat off topic....Would you happen to know when HC-110 was introduced? I can't find any info on that.

Michael Covington's excellent Unofficial HC-110 resource page says 1962: http://www.covingtoninnovations.com/hc110/