Hydroquinone developers

On page 42 of A&T, they discuss the change in activity of D76, and

the solution proposed by Haist to fix this increase in activity.

 

I would like to add that I have seen first a decrease, then an

increase in activity of scratch mixed Dektol, followd by a slow

decrease. After researching this in the literature, I find that

Mees has published the entire sequence of events that causes this to

take place.

 

First, shortly after mixing, HQ is oxidized by air.

 

It then reacts with sulfite to form the monosulfonate which is a

weaker developing agent along with NaOH, (Sodium Hydroxide) and

therefore the pH increases.

 

You can see an increase in activity due to NaOH alkalinity as

reported by Mees and later by Haist, and a decrease in activity due

to the HQ monosulfonate being a weaker developing agent as reported

by Mees. (I have stated here in a previous post that the HQ

monosulfonate is hihger in activity, but what I was really seeing, as

Haist did, was the increase in activity due to the production of

NaOH, although I saw it in Dektol and did not connect the two

situations.)

 

In "The Chemistry of Photography", Chapman discloses that the E6 MQ

developer uses HQ monosulfonate instead of HQ. I believe that this

imparts a twofold advantage to the E6 process. First,

it 'preseasons' the MQ by using the oxidation product of HQ, and

secondly it uses a milder developing agent for more uniform results.

 

So, E6 MQ formulas with HQ probably will not work as the manufacturer

intended, ie. in a manner that the film has been designed for.

 

What does this mean?

 

First, it means that the situation with any HQ developer is more

complex than described previously. There are complex interactions

wich lead to changes in activity.

 

It also means that any HQ containing developer is subject to some

sort of activity change over the first few days of life after

mixing. Then, the developer reaches its peak 'ripeness' and

gradually dies of old age. I have found in practice that keeping a

HQ containing developer for about 1 day and then using it will

greatly damp out this type of change.

 

I also suspect it means that EK may have altered some HQ formulas to

use an equivalent amount of HQ monosulfonate or otherwise has altered

formulas to mitigate this effect imposed on us by HQ decomposition.

 

Ron Mowrey

Makes me feel better about switching to XTOL. Maybe. But who knows what it's doing?

One of the BIG negatives of powder developer vs. liquid developers is as you have described. A technique that we use to compound powders is to tumble the HQ with the NaOH until the HQ is coated. This prevents the oxidation reaction during shelf life. Once the developer is put into solution, it begins to oxidize immediately. We use phenidone as oppossed to Metol (Elon). Phenidone is a much more powerful accelorator than Metol and much more resistant to oxidation and heat. Phenidone combines with the HQ to develop the exposed silver halide crystal and then searches for more HQ to work with until the HQ is exhausted. Resulting in a gradual slide in activity. Metol forms a salt with HQ and is done, or "drops in the ocean" and dies.

Lowell;

 

You may be making the Sodium salt of HQ. Have you ever checked that out? Do you mill it under dry nitrogen?

 

Also, Dimezone seems to be a little better than phenidone IMHO.

 

Ron Mowrey

Am I correct in assuming that the change in activity is due to changes in pH?

 

Is that why Kodalk (balanced alkali) that acts like a buffer solution, keeping the pH at 10 for longer time is better?

Pablo;

 

Activity goes up due to formation of NaOH, and down due to the loss of HQ. It is a question of buffering capacity and activity which would differ for each developer formulation.

 

Any buffer would help retard the pH change to some extent. I would think that Sodium Carbonate - Bicarbonate at 10.0 would be the best, having tested it and it is also more environmentally friendly.

 

Ron Mowrey

This is interesting stuff Ron, thanks for posting it. It makes good chemical sense that the sulfonate of HQ is a poorer reductant than HQ itself, though I need to work out for myself how the EAS reaction generates hydroxide. I would think that the ability of the HQ to be absorbed into the emulsion would also be affected by sulfonation, which would be yet another factor. Lots of complex chemistry going on here -- the chemistry of quinones is rich and is also of key biological importance, as they are critically involved in photosynthesis.

 

Hydroquinone can be easily substituted in the 2 or 2,5 positions with halogens. These substituents wouldn't massively affect the redox potential of the hydroquinone but they should shut down the sulfonation reaction. I remember reading about the use of halogenated hydroquinones in Haist but I can't remember what he said about them. As per others' findings that HQ acts as a staining developer in the absence of sulfite, I would predict that these derivatives would have some staining effect.

 

The use of the HQ sulfonate as a starting material is also intriguing but I think you get there either way. Its use would certainly take away the 'ripening' factor.

 

Jordan

Jordan;

 

Mees and Mees and James both give the order of reactivity of the HQ family. Makes interesting reading. I've been reviewing this chemistry for the last week or so.

 

If you can get a copy of either book, it is fascinating reading.

 

Ron Mowrey

Ron,

 

I've always had a slight wariness of MQ developers for the reasons discussed above. Semi-quinones produced when hydroquinone oxidises are much more vigorous developing agents particularly in more alkaline environments (cf. the chemistry of infectious development). For this reason I have always fought shy of MQ formulations, accepting Bob Scwalbergs injunction to lean towards single developing agent formulations (in my case Rodinal). Other than that I have used D23 at 1+2 to avoid the vagaries of quinol.

 

In the past when I have mixed MQ developers, I have always dropped a piece of scrap film in to put some bromide into solution or added a few ml of 'old' developer which likewise contains bromide ions.

Chris;

 

Pre-seasoning with bromide is a two edged sword. As you all know, D76 is a halide free developer with high solvent. This developer seasons rapidly with bromide, but bromide controls whatever edge effects that D76 is capable of giving in the face of so much sulfite as solvent.

 

The chemistry becomes so complex that it boggles the mind, and the end result can affect sharpness, grain and contrast.

 

Semi-quinones can be a problem as you point out, but hopefully short lived due to equillibration - perhaps.

 

Phenidone might be an answer, but IMHO Dimezone is better. I have worked with both and Dimezone seems to me to be better, but I think that someone else would have to make that call rather than me. I don't have enough time to do the work justice.

 

Pyro seems to be another answer, but it too oxidizes rapidly and is toxic, although apparently not as much so as made out by some (myself included - but I'm very concerned about toxic chemicals having worked with some really really toxic stuff in my days). I have been reading up on Pyro and have purchased some Formulary kits to give them a go with a box of TX pro sheet film and see what I come up with.

 

Actually, this may surprise many of you but my latest shots using Portra 160VC and 400 UC and comparing to Delta 400, 3200 and TX in both 35mm and 120 sizes shows better overall grain and sharpness goes to the color films. Even in the B&W prints from the color films at high magnification show better sharpness and grain. I may try some chromogenic B&W.

 

Right now, I'm experimenting with C41 at room temperature. I hate running at 100 deg F. I'm now printing B&W and RA color at the same temperature - 68 - 75 deg, and getting excellent results with both but with the B&W developers, I have to age them a tad to normalize the activity.

 

The development time required for C41 films at 75 degrees right now seems to be longer than 9 minutes. That is a big slice of time to pay for the temperature offset. I'm still working on it though.

 

Ron Mowrey

I forgot to add part B to my question....

 

Is this why the "old brown" method is reccomended to "mellow" a developer?

 

Does this happen woth PQ developers? I'm using ethol LPD and haven't seen a large decrese in activity

I personally have no idea Pablo. Sorry I can't help.

 

Ron Mowrey

Ron,

 

I'd be interesting hearing about your results for room-temp C41. Anything that gives that process anything near the convenience of the standard B&W process would be great for me! Actually, 9 mins is not that long. Do you alter the composition of the developer to compensate for the reduced temperature? Are there major filtration changes involved?

 

Also, I'm having a hard time 'parsing' your author list for the two books. What are the titles of the books? Mees (at least one Mees) wrote quite a few, it seems.

Sorry.

 

Mees "The Theory The Photographic Process"

 

Mees and James - same title, is the next edition of the previous citation, much updated and much more complete.

 

The page in the first reference is 561.

 

The reaction is as follows:

 

HQ + 2Na2SO3 + O2 -> HQSO3Na + Na2SO4 + NaOH reaction # 20 on that page.

 

Ron Mowrey

Sorry again. Forgot your C41 question...

 

I'm working on it yet. No concrete results that I would care to publish here. All I know is that the development time appears to be longer than 9 mins under my conditions.

 

Ron Mowrey

The fact that hydroquinone developers tend to raise pH while ascorbate or erythorbate developers tend to lower it is responsible for different "edge effects" of the two. It is also interesting that PQ or MQ developers need sulfite for synergism while PA or MA developers do not.

Patrick;

 

Interesting observation, but since classic edge effects are due to bromide inhibiting development not pH effects, can you give me any examples to look at or any references? Mees makes no mention of this, but does refer to the halide effect for example.

 

It could only be a pH effect in poorly buffered solutions, isn't that correct? For example, D76 is considered poorly buffered. A carbonate - bicarbonate developer would be well buffered at about 50 g/l carbonate and perhaps 10 g/l bicarbonate adjusted to 10.0.

 

Ron Mowrey

I only repeated what I read somewhere. In theory, the ascorbate loses 2 H to form with 2 Br, from reduction of the AgBr, both 2HBr and dehydroascorbic acid. The first is obviously acidic as well as bromidic, while the second is slightly more acidic than ascorbic acid, but has no developing action that I have heard of. In the case of hydroquinone, as you pointed out, the pH is somewhat higher, which may counteract to some degree the bromide produced. I have seen very sharp edges from both kinds, but I would expect to see, maybe, somewhat of a non-minimum phase response to a step input in the ascorbate developer and a bit of overshoot in the hydroquinone. I can't remember my reasoning for that and I don't have the laboratory equipment to test it scientifically. I know the local change in pH adds to bromide effect in one case and subtracts in the other.

Patrick;

 

I too am in no position to test this out, but it does seem to me that the interactions are so complex that a rather huge factorial experiment would be required involving both HQ and AA developers. I know of one person only that may have done it. I will have to ask him next time I see him.

 

I'll let you know if I do indeed remember to ask him. I'm probably going to see him at the next KRL retirees lunch in about 2 weeks. It seems to me that the experiment was indeed done. If so, it was an Elon Ascorbic Acid developer in the one case, vs HQ and Elon in the other. Do you see that as being a problem in the comparison?

 

Ron Mowrey

Most EK developers have considerably more sulfite than I use with ascorbates, which is usually none. I don't know if that has a relative effect. I do remember that the designers of XTOL in their introductory article in Photo Techniques remarked that both resolution and sharpness were better in their system of comparison than MQ or PQ developers. IIRC, they attributed it to the fact that ascorbic acid (in the case of XTOL, isoascorbic or erythorbic acid) is a surface developer, meaning the surface of each crystal I believe. it is also referred to as such in the "Theory of the Photographic Process."

 

I tried XTOL when it first came out and thought it was a fine developer, but I had been using my own Vitamin C one-shot mix-as-you need formula since early 1994, and when the Xtol was gone, I never bought any more. Now, I have no irrepressible longing to get a 5 liter package for comparison with my latest magic potions.

 

I would be surprised if someone at EK had not tried sulfite-free ascorbate developers. Perhaps they might have produced one if they had thought of replacing the hydroquinone in HC110 with isoascorbic acid to make a long lasting concentrated stock without sulfite. If they had, I would probably buy it myself. Ilfotec HC comes fairly close, but also contains hydroquinone and a sulfite complex.

 

To make a long story only a little bit longer, If you find that someone has compared by microdensitometer or whatever what we want to see, ask if they ever tried it with out sulfite for the ascorbate and minimum sulfite for the hydroquinone.

I should have said "Ilfosol-S" instead of "Ilfotec-HC". Ilfosol has both hydroquinone and ascorbate, with emphasis on ascorbate. Ildotec-HC is pretty much like HC110.

Thanks very much Patrick.

 

I have printed this out, and if I can get a chance to talk to some of my resources at our retirees lunch later this month, I'll have this either with me or memorized so I can get further information on it to you.

 

Ron Mowrey