Vitamin C in divided developer?

I'm aware that ascorbic acid (or erythorbic acid, for that matter) can't be preserved in developer working solutions by sodium sulfite -- it's a more active antioxidant than the sulfite. However, it just occurred to me, while reading the thread on Split D-23, that I'm not sure how Vitamin C holds up in a neutral to acidic divided stock solution.

Does anyone know, can I make a water based concentrate or stock solution of or containing ascorbic or erythorbic acid and have it keep long enough to compare to conventional developers? Or is it going to go off on me in a few hours or days? Yes, I know there are non-aqueous concentrates (like PC-TEA); I'm interested in the possibilities for a divided developer using vitamin C or equivalent.

And if no one knows, I can test, but I thought I'd save myself a dollar's worth of vitamin C if someone knows it won't work...

It is not true to say that sulfite does not function as a preservative in ascorbate developer solution. In my testing, oxidation and loss of ascorbate in developer concentration sharply increases when much of the sulfite is lost by oxidation.

If you don't do anything special to preserve ascorbates, it is more likely that the ascorbate solution dies sooner in more acidic stock. I don't recommend acid stock solution for ascorbates.

If you are trying to make a two bath developers, I should also note that the first bath should be weakly alkaline, like pH of 7.5 to 8.3. Acidic first bath would not develop the film enough, even if the second bath is fairly alkaline. Some of the popular developer books contain misconception on this issue.

There's a way to make ascorbate developer last long. See my DS-12 film developer and DS-14 print developer. They last long enough to be practical. DS-10 is a very good fine grain film developer, but it should not be kept for more than a couple of weeks, as I've seen cases where developer went off after that period. Effort to improve this is ongoing.

Donald Qualls said:

Does anyone know, can I make a water based concentrate or stock solution of or containing ascorbic or erythorbic acid and have it keep long enough to compare to conventional developers? Or is it going to go off on me in a few hours or days? Yes, I know there are non-aqueous concentrates (like PC-TEA); I'm interested in the possibilities for a divided developer using vitamin C or equivalent.

And if no one knows, I can test, but I thought I'd save myself a dollar's worth of vitamin C if someone knows it won't work...

Click to expand...

Interesting you should ask this just one day after I experimented with dividing my tried-and-true Phenidone/Vitamin C/Metaborate developer. In a word, it didn't work. Perhaps Ryuji's answer gives me a clue where to go from here, but I just did a simple experiment: exposed two rolls identically, and developed them for two different developing times, one at three minutes in each bath, and the other at six. Neither roll had a visible image--- just clear film.

I put the Phenidone/Vitamin C in bath A and the metaborate in Bath B. I should have tested the pH of Bath A but forgot to do that. I have used divided D-76 and divided D-23 many years ago, but hadn't tried it since I began using my current PCM soup.

Larry

I don't know the answer to Donald's interesting question.If air is excluded I don't see why a concentrated PC part A solution should not be stable.A solution with no sulfite might preserve the edge of grain sharpness which is a limitation of the 2 bath developer I sometimes use.

Ryuji said:

If you are trying to make a two bath developers, I should also note that the first bath should be weakly alkaline, like pH of 7.5 to 8.3. Acidic first bath would not develop the film enough, even if the second bath is fairly alkaline. Some of the popular developer books contain misconception on this issue.

Click to expand...

Okay, this throws my thinking directly into a cocked hat...

It's been my understanding about true two-bath developers like Diafine, Stoeckler, and SD-4/SD-5, that little or no development takes place in Bath A, and (at least with Diafine) contamination of Bath A with the alkaline Bath B results in destruction of the developer (or at least its special properties). Or are you saying that an acidic carry over would reduce the pH of Bath B enough to prevent adequate development in the second bath? I think I can beat that, if that's the problem, by one-shotting Bath B, which is inexpensive anyway (both borax and sodium carbonate are much less than a dollar a pound in technical grade)?

Either way, a mildly alkaline Bath A isn't a problem, except I presently have no means to test pH and ensure it's only *mildly* alkaline -- and if it's more alkaline, too much development will take place in Bath A and I'll get something more like DD-23 than, say, DD-76. I suppose I could add tiny amounts of bicarbonate or carbonate until no foaming occurs; a sort of titration, using gas evolution as the indicator.

I know there are ways to preserve ascorbate in solution -- XTOL has been doing it (with varying success that I understand was eventually traced to packaging problems) for some years. What I was hoping for, however, was a developer that, like Diafine, I might be able to keep in good bottles, use when I need it, and reasonably expect it to still be good a year or two years later if I haven't just used it up. From what you're saying, it sounds like mildly alkaline solution with lots of sulfite is the right direction.

Of course, there remains the option to mix the 2-bath developer immediately before use; less convenient than having the two solutions in bottles, but it won't go off in minutes, and it would be easy enough to premeasure the dry chemicals into packets that could be mixed in the time it takes to open a bag and pour the contents and water into a graduate. Seems wasteful, but not really any more so than what I'm using now for the applications I have in mind.

Donald,

Several years ago, I had already been preparing my Gainer developer (this was before the PC-TEA and PC-Glycol era) in two baths, one stock solution containing the phenidone and ascorbic acid and the other containing the alkali. In normal use, I would mix them 1+1+8 with water before use. (I can dig up the formulas if you are interested.) They kept fairly well for several months but the developer stock gradually turned yellow over time. I didn't check the yellowed developer for activity, but instead just dumped it.

I once tried to "do a Diafine" on the Gainer developer by soaking my film in the developer solution (without alkali) for several minutes, followed by the activator solution. I got clear film and I didn't pursue it further (either the developing agents didn't soak into the film or the carry-over neutralized the activator, as Ryuji mentions).

The two-bath method does work, but now I just use PC-Glycol (the developing agents are dissolved in propylene glycol and diluted into aqueous sodium carbonate just before use). My stock solution is two years old and is still very active.

This will blacken a film leader,it is not suggested for films.

Part A - 1/4tsp phenidone in 50ml isopropanol,take 10ml of this add to Vit C 1tsp in 50ml water.Soak film leader for 3 min-no color change.

Part B -3tsp sodium carbonate monohydrate in 500ml water.Remove film leader from part A and soak in part B for 3 min - goes black ,not very high density.

The problem is that, when you are reading popular darkroom bibles, you don't know how much of the stuff is oversimplified for the audience the authors assumed. If you give your reading too much confidence without tracing back to all the original research reports, you'll face problems.

Contrary to what's written in common darkroom bibles, two bath development is not like mixing bath A and bath B in the emulsion layer when the film is transported. I do not know of a successful two-bath developer where film is not developed at all in bath A.

In the history of developer technology, two-bath method was studied c. 1930 as a way to minimize chemical waste for motion picture processing. However, research at that time already found that the approach is not very fruitful. The same goal was achieved by replenishing method. If you are worried about chemical cost, this is the way to go. I used to do it with hand inversion tank, and I got pretty reliable results. I could even save developer solution between uses.

Measurement of accurate pH is kinda essential if you do research work in developer chemistry. But this is a lot more than buying a meter, because pH probe is a high maintenance instrument. So I don't know what to tell you on this one. You might want to decide between letting skilled people do the research, or to become the skilled person yourself to do the task.

Using bubbling as an indicator is very unreliable. You should at least get fine grain pH test strips (they come in narrow window of pH range so you need a few different sets). You also might want to get a few pH indicator dyes for different pH ranges. For usual darkroom work, these are often sufficient.

Making ascorbate solution that keeps is not a trivial task. You should search for patent literature, for example. There are numerous inventions for which patents are granted but very few are used in actual commercial products. This is because many inventions obtained from hard work at major manufacturers are also ineffective or not cost-effective enough. I also do try to replicate some of their techniques to see ho wthey work, but some of them don't even work! I have good sense of what is going on in this area but it involves a few branches of chemistry (electrochemistry, coordination chemistry, organic chemistry, etc.) and it's not really a topic for amateurs lacking good background in these areas. A lot of known tricks for MQ or PQ developers do not work with ascorbate developers.

Ascorbate and reductone developing agents are known since c. 1930, but they haven't been used for practical applications until last decade. Even that was partly pushed by environmental regulations. What this tells you is how hard it is to make practical, reliable developers using this agent.

I have also tried making divided ascorbic acid developers, both for paper and film. It didn't work. It may be because the acidic oxidation products of ascorbate inhibit the reaction too quickly. Hydroquinone would be the way to go if you're making a divided developer.

Let me ask about the absorbing of the first part in the gelatine. Many years ago I had no difficulty reticulating Tri-X and other films of the time. Nowadays it is difficult to reticulate most BW films. Then, too, I seem to remember that acidic solutions are not conducive to absorption.

An ascorbate developer need not be acidic to be practically inactive. A combination of phenidone and sodium ascorbate may basic enough to allow absorption into the gelatine without being basic enough to do appreciable development in the first bath. I'm just speculating. A possibility, beside those that Ryuji has suggested, is a phenidone-ascorbic acid solution in propylene glycol with a small amount of TEA enough to make it just a little on the basic side when it is mixed with water.

It is not that the gelatin doesn't swell. Film manufacturers aim about 300% swelling of gelatin used in emulsion layer because this range is optimum in terms of saving silver and obtain high density. This is less swelling than 1950 stuff, but gelatin still swells 300%.

When film is transferred to bath B, diffusion of both directions occur, as in Donnan membrane mechanism. The effective development time in "mixing in gelatin" mechanism is very short. In order to achive effective development in that short time span, development centers must grow to a sufficient size while the film is in bath A. One could say that the induction process must happen in bath A alone.

I personally do not recommend propylene glycol. When a LOT of it is present in developer solution, it may be effective in prolonging the stock's shelf life, but if you use it in split stock solution, it is very easy to infringe one of the Kodak patents. Another problem with propylene glycol (and actually many alcohols and glycols) is that when the stock solution is diluted, so that the glycol concentration becomes low enough, the presence of PG can actually accelerate aerial oxidation of ascorbate compared to when there is no PG! I did tests on this with an array of solutions stored in bottles with aerobic stoppers for 2 months, at that point developer composition and chemical activity were measured.

Triethylene glycol is slightly better than propylene glycol in this regard, although TEG also accelerates ascorbate loss. I think that PG is more effective in oxidizing ascorbate because two alcohols are vicinally positioned to increase binding to metal impurities. If so, compounds like 2,4-pentanedione (acac) would be more effective in killing ascorbate. Anyway, beware of nonaquaous solvents.

I'm trying to do the opposite of what's described above by making some derivatives of those compounds that posses desirable properties. Let's see how it goes...

Ryuji said:

Using bubbling as an indicator is very unreliable. You should at least get fine grain pH test strips (they come in narrow window of pH range so you need a few different sets). You also might want to get a few pH indicator dyes for different pH ranges. For usual darkroom work, these are often sufficient.

Click to expand...

Donald - I suggest something like the Whatman multistrip indicating papers Dead Link Removed
I use the CF paper which measures from 0-14 with about 1 pH resolution, for making quickie pH measurements. You can get papers that are in narrower ranges too if you have a range you want to focus on.

Of course, these aren't as high-tech as an actual meter, but as Ryuji points out on his web site - there are a lot of things to consider with the meter route to make good, reliable pH measurements. And for what you are doing, I think the strips will be quite helpful.

Kirk - www.keyesphoto.com

Kirk, good suggestion, but I have no budget whatever here -- I'm trying to learn something and possibly produce something with what I have on hand. And since there's an expert opinion that nothing I can possibly do will produce a workable divided developer with ascorbate, I'll just go away.

To cite a early 20th Century comment: Insects can't fly (a simplified translation of Magnan's statement in his 1934 book).

In 1934, French entomologist Antoine Magnan included the following passage in the introduction to his book Le Vol des Insectes:


Tou d'abord poussé par ce qui fait en aviation, j'ai appliqué aux insectes les lois de la résistance de l'air, et je suis arrivé avec M. SAINTE-LAGUE a cette conclusion que leur vol est impossible.


Magnan's reference is to a calculation by his assistant André Saint-Lagué, who was apparently an engineer.


This statement eventually morphed into: "Like the bumblebee, they said it could never fly."

http://www.sciencenews.org/articles/20040911/mathtrek.asp

Ryuji said:

It is not that the gelatin doesn't swell. Film manufacturers aim about 300% swelling of gelatin used in emulsion layer because this range is optimum in terms of saving silver and obtain high density. This is less swelling than 1950 stuff, but gelatin still swells 300%.

When film is transferred to bath B, diffusion of both directions occur, as in Donnan membrane mechanism. The effective development time in "mixing in gelatin" mechanism is very short. In order to achive effective development in that short time span, development centers must grow to a sufficient size while the film is in bath A. One could say that the induction process must happen in bath A alone.

I personally do not recommend propylene glycol. When a LOT of it is present in developer solution, it may be effective in prolonging the stock's shelf life, but if you use it in split stock solution, it is very easy to infringe one of the Kodak patents. Another problem with propylene glycol (and actually many alcohols and glycols) is that when the stock solution is diluted, so that the glycol concentration becomes low enough, the presence of PG can actually accelerate aerial oxidation of ascorbate compared to when there is no PG! I did tests on this with an array of solutions stored in bottles with aerobic stoppers for 2 months, at that point developer composition and chemical activity were measured.

Triethylene glycol is slightly better than propylene glycol in this regard, although TEG also accelerates ascorbate loss. I think that PG is more effective in oxidizing ascorbate because two alcohols are vicinally positioned to increase binding to metal impurities. If so, compounds like 2,4-pentanedione (acac) would be more effective in killing ascorbate. Anyway, beware of nonaquaous solvents.

I'm trying to do the opposite of what's described above by making some derivatives of those compounds that posses desirable properties. Let's see how it goes...

Click to expand...

Without contradicting what you have done, I don't think it is what I have done. As you said, the use of glycols preserves the stock solution. A simple solution of ascorbic acid and phenidone is useful. The working solution needs not last any longer than the developing time, and I have not seen it fail. When it comes to patents, it is difficult to patent anything that would likely be designed by a competent engineer. Perhaps you can inform me who was first to use a glycol as a solvent for developing agents, and if the first one tried to patent that process. It is quite common for engineers to search for useful solvents among many possible useful ones. The Patent Office will often grant a patent, but will not defend it for one.

Come to think of it, I'm not sure anyone ever tried to patent water as a solvent for photographic chemicals.

Patrick, patent is a conceptually simple system but in order to understand how it works, you should spend some time studying the system. Much of what you said are irrelevant to the criteria of patentability.

A lot of things can be patented. It mostly depends on how you write claims and support claims in the specifications. There are lots of VERY funny examples, but check out US Patents 5443036 and 5851117 for example.

Patent examiners have a set of legal standards to decide whether the invention is patentable as described in the application. Good patents have a set of very strong, broad claims (independent claims) and a lot of specific claims derived from the independent claims (dependent claims). Good claims are ones that good implementations would have to infringe at least one of them. But if the invention is weak (not novel enough, not useful, or too obvious to those skilled in the art) patent examiner will negotiate to strip down the claims or make claims narrower. Consequently, if the invention is not very strong, it may be patented but the claims are virtually useless and many people could implement the idea without infringing any of them.

On the other hand, details disclosed in the specification must support the invention and they also have to disclose the best mode of implementation known to the inventor. Regardless of how useful or useless the claims are, what's written in the specification can be used as a reason to reject future applications of inventions using that knowledge as a key element. Thus patents have two major aspects of defining your legal rights related to your invention. If you want to know more, you should consult a patent attorney or consultant.

Use of water as a solvent for developer is clearly not patentable alone, but if there are enough specifics to make the case special, it may be patentable. But this is true of many things.

Donald Qualls said:

Kirk, good suggestion, but I have no budget whatever here -- I'm trying to learn something and possibly produce something with what I have on hand. And since there's an expert opinion that nothing I can possibly do will produce a workable divided developer with ascorbate, I'll just go away.

Click to expand...

I didn't mean to discourage you or anyone, but I merely pointed out that the problem you were dealing with is not a trivial one for amateurs.

Now the pH problem, since Kirk continued on that issue.
In my experience of phenidone-ascorbate developers, in very general terms, the developer pH difference of 0.2 is photographically very significant, even to a casual observer without formal sensitometry, especially if the developer pH is below 9.3 or so. I try to adjust pH to plus/minus 0.05 for film developers.

A good developer design would have to be that, when a batch of developer is mixed with reasonable care, the solution pH is well within the target pH window, and the developer performance is robust against small errors in chemical weighing, film difference, exposure difference, etc. I understand that most people on apug are darkroom hobbists who make the chemicals for themselves, without worrying too much about reproducibility and robustness, but these are definitely important practical aspects and pH is one of the most fundamental values to be controlled.

The use of polyoxy, polyhydroxy and polyamino addenda in developers (read poly ethylene and propylene glycols, poly vinyl alcohols, and poly vinyl pyrrolidones) along with TEA and a host of other amines have been known since the 50s.

Many many patents have issued on these addenda, and many overlap with couter claims and claims within claims.

In some cases, you might find yourself infringing a whole set of patents with one of these compounds at one concentration, and end up theoretically owing redress to several companies at one time. Then the courts would have to figure out who got what if anything.

Expired patents are of no concern for any infringement purposes. They are free to use in any way.

PE

Ryuji said:

Another problem with propylene glycol (and actually many alcohols and glycols) is that when the stock solution is diluted, so that the glycol concentration becomes low enough, the presence of PG can actually accelerate aerial oxidation of ascorbate compared to when there is no PG!

Click to expand...

Have you tried PEG - polyethylene glycol - about 200 MW? (I happen to have a bout 500 ml sitting on the shelf looking for a good use.)

Any advantage to using larger glycol molecules?

Two suggestions re the original question.Simple may not be optimal but may be good enough to get started.

1-Afairly concentrated solution of vit C and phenidone may get enough ascorbate into the emulsion to cause development in sodium carbonate.

2-A solution of sodium ascorbate as part A may be more stable but it is harder to get I believe.

IIRC the phenidone should be about 1/40 the ascorbate by weight.

Ryuji, as I'm sure you know, propylene glycol and pentanedione are very different ligands. I am not an inorganic chemist, but alcohols generally do not have a significant interaction with redox-active metal ions in aqueous solution. Even with the chelation effect, I think that a metal impurity (say Fe) is much more likely to be hydrated (harder ligands) than to form a five-membered chelate with propylene glycol.

I would suggest that the differences you observed may be due more to impurities introduced into the developer solution by the various glycols, but of course I don't know for sure.

Kirk, PEG 200 is mostly the tetra- and penta-oligomers of ethylene glycol. Pretty viscous stuff, right? I'd imagine it would be pretty hard to work with due to the viscosity. I'm not sure what advantage it would provide... though it may be worth a try... (by the way, pure tetra-EG and penta-EG are available from places like Aldrich, but the mixed stuff is cheaper I think).

Finally, someone can correct me if I'm wrong, but I'm surprised about the concerns over patents here. A patent gives its owner a commercial monopoly on the inventions described in it, right? Violation of a patent can only take place when commercial activity is involved -- or am I wrong?

The use of propylene glycol as a solvent for developers is an interesting idea and one that has worked for me. My PG stock solution of ascorbic acid and phenidone has lasted two years without a significant decrease in activity (but I don't have a densitometer and don't run test strips). When I dilute it in aqueous base, it doesn't sit for more than 10 minutes before I develop my film, so I don't know about the lifetime of the working solution.

It's clear that the phenidone-ascorbic acid developers prepared as organic stock solutions are very poorly characterized and not rigorously tested. If I were a pro that demanded absolute roll-to-roll consistency, I would stay far away from these soups (and probably most other home-brews). But I (like most of the posters here, I think) am just a hobbyist in the photo world, I like goofing around with this stuff, and in this case it works. It may not work (or fail catastrophically) for some, but then again there are commercial developers have been known to do the same.

Anyway, my $0.02...

Getting back to the question of whether a PC divided developer is possible, I recently remembered that Paterson's FX-50 is advertised as being useable either in single-bath or two-bath ways, and it's a PC developer. This seems to suggest that a PC divided developer is possible, but I don't know how FX-50 does this.

Ryuji said:

Patrick, patent is a conceptually simple system but in order to understand how it works, you should spend some time studying the system. Much of what you said are irrelevant to the criteria of patentability.

A lot of things can be patented. It mostly depends on how you write claims and support claims in the specifications. There are lots of VERY funny examples, but check out US Patents 5443036 and 5851117 for example.

Patent examiners have a set of legal standards to decide whether the invention is patentable as described in the application. Good patents have a set of very strong, broad claims (independent claims) and a lot of specific claims derived from the independent claims (dependent claims). Good claims are ones that good implementations would have to infringe at least one of them. But if the invention is weak (not novel enough, not useful, or too obvious to those skilled in the art) patent examiner will negotiate to strip down the claims or make claims narrower. Consequently, if the invention is not very strong, it may be patented but the claims are virtually useless and many people could implement the idea without infringing any of them.

On the other hand, details disclosed in the specification must support the invention and they also have to disclose the best mode of implementation known to the inventor. Regardless of how useful or useless the claims are, what's written in the specification can be used as a reason to reject future applications of inventions using that knowledge as a key element. Thus patents have two major aspects of defining your legal rights related to your invention. If you want to know more, you should consult a patent attorney or consultant.

Use of water as a solvent for developer is clearly not patentable alone, but if there are enough specifics to make the case special, it may be patentable. But this is true of many things.

Click to expand...

I studied this subject along with our legal staff when I worked at NASA. No matter what the Patent Office does in granting a patent is not incontesatble, and it is not their job to defend that patent. They can testify, but in a case where it turns out that they were wrong, the patent will not be enforcible. If one tries to patent a device or process that any competent engineer would derive as a matter of course in the process of solving a problem, that patent application should be denied. I don't see how a person could patent the process of dissolving photographic chemicals in a common organic solvent. That is much too general and in fact could could and would have been in violation of the patent even before it was issued.

Shooting bliind here... but a pool pH kit may be a cheapo solution?

Donald Qualls said:

Kirk, good suggestion, but I have no budget whatever here -- I'm trying to learn something and possibly produce something with what I have on hand. And since there's an expert opinion that nothing I can possibly do will produce a workable divided developer with ascorbate, I'll just go away.

Click to expand...

Here is an experiment I did-2VIT-C 91205

Part A: Phenidone 1g in 50ml isopropyl alcohol,add to Vit C 50g in 400ml distilled water,make up to 500ml,filter cotton wool.

Part B: Sodium carbonate anhydrous 15g in 400ml distilled water, make up to 500ml.

Precaution-high phenidone content,used rubber gloves.Some of the concentrations may be way over the top as I tried to avoid a blank film. Film-Delta 100,pictures of tree,sun/shade. Times-3min Part A, 3min Part B 75F.

Result-EI 125 (I get 160 with Emofin),quite high density for an ascorbate,some base fog.The negs were not printed but the grain looks sharp-sulfite free that was the idea.I hope to repeat the test in a month or so to see if part A is stable.