Direct effect(s) of alkalinity on granularity

Discussion in 'B&W: Film, Paper, Chemistry' started by Michael R 1974, Apr 15, 2014.

  1. Michael R 1974

    Michael R 1974 Subscriber

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    This was originally a PM to PE but I figured I'd make it a thread in case anyone is interested.

    This concerns the DIRECT influence (if any) of pH on granularity.

    We often read that when it comes to fine grain development, pH is an important factor. More specifically, the contention is that in the context of fine grain development it is important to have relatively mild alkalinity. The indirect reason for this is well established – ie all other things being equal, lower alkalinity means a longer development time and therefore more time for the sulfite to etch away at the crystals.

    But then there are those supposed direct effects of higher alkalinity. Everything from gelatin softening to “clumping”. One of the problems is “clumping” as a descriptor for an effect (increased non-homogeneity of developed silver for a given density) is used by different people to describe the overall effect of a few different causes/mechanisms. Some of them may be valid, some may not.

    For example, to most people “clumping” in the context of high alkalinity means the actual grains clump together as development progresses, presumably further facilitated by the softening of the gelatin. This is sometimes referred to as "grain migration". Zawadzki addressed this in one of the Myths columns she used to co-author with Dickerson in Photo Techniques. To quote her: “Doesn’t happen”. However, Haist may have had a different view: “Developing solutions for producing fine-grained images should reduce the silver from each grain in place in the gelatin layer. To achieve this aim, the solution must be relatively low in alkalinity. Highly alkaline solutions cause the gelatin of the emulsion layer to swell and soften more than solutions at lower pH.”

    How about another cause for the clumping effect, one having to do with the actual formation of the metallic silver filaments themselves. Suppose there is no actual “grain migration” at higher solution alkalinities. In that case, what difference would pH per se make when it comes to non-homogeneity of developed silver (ie increased granularity)? In the same paragraph Haist goes on to say “High alkalinity also causes a more rapid and vigorous formation of silver filaments. Both the softened gelatin and the vigorous formation of the silver particles increase the possibility that the silver filaments will be larger and more nonuniform in distribution.”

    So, I’m still unclear on whether or not alkalinity (within reason and barring extremes) directly affects granularity. Perhaps gelatin swelling can indeed cause some sort of deformation even if the grains themselves don’t move within the gelatin. On the other hand, current Kodak and Ilford films are well hardened.

    Here is PE's initial response:

     
  2. Michael R 1974

    Michael R 1974 Subscriber

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    I figured I'd add some thoughts on a possible experiment. Suppose we took solvent effects out of the equation (because it would be extremely complicated to formulate the experimental developers if they were solvent in nature). In other words, as little sulfite (or any other compounds which might promote solvency) as possible.

    A suitable "control" developer might be the Beutler formula (Metol, a small amount of sulfite, carbonate alkali). Crawley's FX-1 might also do. Then suppose we ran an experiment in which the formula was adjusted to replace the carbonate with a small amount of say borax, or even sodium bicarbonate perhaps. Ideally what we'd have (albeit with a much longer development time) is a developer that (hopefully?) (possibly?) duplicated the sensitometric characteristics of the control developer with a given film, still with minimal/no solvent effects, but at a significantly lower pH.

    Suppose that could be done. What differences might we see (if any), in graininess?

    Of course as PE reminds us, you can't have everything, and there might by other image structure tradeoffs (sharpness for example). But keep in mind this thought experiment is strictly from the perspective of granularity/graininess in relation to pH.
     
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  3. dwross

    dwross Subscriber

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  4. Ian Grant

    Ian Grant Subscriber

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    It's a wide open topic because there are developers like Rodinal with a high pH which give excellent fine grain and there's also developers with almost neutral pH which are very fine grain, it''s dependant on the overal developer formulae and the developing agent(s) used.

    Ian
     
  5. Photo Engineer

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    Rodinal was one of the developers that I had in mind, but there are so many work alike developers I hesitated to get into specifics on that topic.

    PE
     
  6. momus

    momus Subscriber

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    I'm probably the least scientific minded person you could ever meet in terms of training and education, but I'm pretty good at observing and noting results. I know for a fact that my D76 used to get more active (higher PH) over time, and the grain got out of hand at some point. It was giving me fits with increased contrast and grain compared to the first negs I developed in it. Switching to TD-16 solved that issue. Before doing that I chased a number of false phantoms like switching to glass bottles, using saran wrap on the tops, glass marbles, etc. Now I just store the developer in those plastic brown bottles from Freestyle. Development is absolutely consistent over at least a 3 month time span now, whereas w/ the D76, 3-4 weeks was all I could get.

    That may not answer your question per se, but to me it means that w/ this particular developer, an increase in PH equals an increase in contrast and grain. Of course Kodak saw the same thing decades ago and is supposed to have fixed the problem w/ their new formulations, yet for me, their new, improved D76 exhibited all the same problems of the old D76. Fortunately, the new stuff retains all of the same excellent developing characteristics as the old, just not for very long, at least in my house.
     
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  7. Michael R 1974

    Michael R 1974 Subscriber

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    We have to make sure it's "apples to apples" for a variety of variables. We know that the degree of development directly affects granularity, so it would be important in any comparison to make sure a careful sensitometric analysis is done first, particularly contrast.

    Within a B&W context, part of the problem is we can't really find commercial products which are comparable. High pH developers are also typically formulated as "acutance" formulas, with properties besides pH per se which don't promote fine grain. And fine grain developers are typically formulated not only to work at a relatively low/mild pH, but they also contain a lot of sulfite. Too many variables there.

    I'm not entirely convinced the developing agent per se is a significant direct determinant of granularity. I can't find any evidence of this (with the obvious exception of PPD which on its own promotes solvency). Furthermore at the microscopic scale, it becomes even more counterintuitive in some cases. With agents such as Metol and Phenidone, which are active at low alkalinity, the formation of metallic silver is apparently relatively "violent", with the original geometric structure/shape of the grain being more or less obliterrated, while Hydroquinone (a compound requiring much higher alkalinity, and one we don't normally associate on its own with "fine grain") apparently allows the shape of the original grain to remain relatively intact.

    Rodinal is another interesting example of a high pH, low sulfite developer. Ian - in your view does it truly give fine grain??

    One of the reasons for this thread is a "fear" I've always had of high pH developers from the perspective of graininess, and it was troubling me recently in some work I was doing on some experimental formulas. I'm trying to figure out whether or not the fear is well founded. So far the scientists seem to be in conflict (I'll add Troop to this list - all over the FDC the point is made that low alkalinity per se is important for fine grain).

    PE - any thoughts on whether or not my proposed experiment has any merit?
     
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  8. dwross

    dwross Subscriber

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    amazing
     
  9. Michael R 1974

    Michael R 1974 Subscriber

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    Meaning what, exactly?
     
  10. Ian Grant

    Ian Grant Subscriber

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    I think if you take a specific developer formula (and dilution) and look at the effects of increasing or decreasing the pH ylou can have a valid "Direct effect of Alkalinity on Granularity".

    However high alkalinity can have adverse effects on surface artifacts of an emulsion, causing apparent graininess in scans or prints. TMY and Neopan 400 were the most susceptible. This is due to softening of the super-coating.

    So Rodinal used carefully can give superb fine grain, with bad temperature control it has a reputation for being very grainy. Many years ago now the late Peter Goldfield who'd worked with Minor White championed the use of Rodinal with modern T grain emulsions APX25 or 10, Tmax 100 & 400, I was highly skeptical until I tried APX100 & Tmax 100 in Rodinal myself. My 35mm negatives with both films in Rodinal are extremely fine grain and very sharp and great tonality.

    Ian
     
  11. Photo Engineer

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    Michael, your experiment seems fine to me, but remember that the overall content of the developer may be critical in getting good results. Even dilution matters as is seen with many developers.

    And, BTW, the pH change in D76 is well known and commented on by Haist. I most always keep my D76 for 1 day before using it.

    PE
     
  12. Michael R 1974

    Michael R 1974 Subscriber

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    Thanks for the feedback, everyone. I think I will try to set up the test I outlined and see if I can come up with any meaningful data for a Metol developer. I don't know that it will be possible, but worth a try.
     
  13. Rudeofus

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    Michael, I think we can not and should not generalize "low pH" and "high pH" developers. There is a profound difference whether you change pH of a single development agent formula or a formula where two development agents work together. And we know that even the interaction between two development agents can be different, remember PEs thread about electron transfer agents vs. superadditivity. For that reason I do not think that an experiment with divided D-23 will tell you much about Phenidone+Ascorbate developers.

    Another issue I would like to raise is the effect of Sulfite on granularity. I keep reading that it "etches into the grain" which is a gross misrepresentation of what's going on. Sulfite will not etch away any Silver, the grain you see in enlargements is not the individual Silver particles, and etching away part of the Silver particles (e.g. with a Ferricyanide bleach) won't change the granularity of your image. From what I have understood, Sulfite ions can bind Silver ions which then allows for physical development, which puts tiny Silver particles between the regularly developed Silver. If my understanding is correct, this action should reduce sharpness, and I wonder whether the effect is much different from a slightly defocussed enlarger lens.
     
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  15. piu58

    piu58 Member

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    The most important thing og pH is that it lowers or rises the activity of the developping substance. There is less value of changing the pH largely with a given reduction substance. This lead to uncomfortable short or long developping times.
     
  16. Michael R 1974

    Michael R 1974 Subscriber

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    Rudi, I agree I would not generalize about the effect of pH, and indeed developers with superadditive combinations are quite different than single agent formulas. So I would like to reiterate/clarify some things:

    1. The experiment I propose has nothing to do with divided/two-bath development. I don't think an experiment with different alkalis in a divided process would necessarily tell us enough about the direct effect of pH on granularity because the sensitometric/densitometric characteristics can change. Too many variables. In addition, D-23 contains a lot of sulfite, further complicating the situation.

    2. The experiment I'd like to try would involve alkali substitution in a Beutler-type developer. Metol, very low sulfite, and alkali. The idea would be to try (if posssible with extended developing time) to duplicate, as closely as possible, the characteristic curve of the carbonate developer with a milder alkali. The low sulfite level would take solvent/physical development effects out of the equation. And no superadditivity would be involved.

    Regarding "etching", this is a complex topic as you know, and indeed the way many people describe the effects and what we see, is a misrepresentation - particularly regarding edge sharpness of image detail. This was something I tried to challenge in another thread regarding traditional acutance and solvent effects. What we perceive as "grains" in a developed image are aggregations of developed silver (filamentary, compact etc.), and in most cases no matter what the magnification there is little if any remnant of the actual shape, borders, or clean edges of the original grains.

    We do know that sulfite (as well as other agents) dissolves the silver halide grain, etching and pitting it. If enough of this action can take place before the latent image centers are chemically reduced to metallic silver filaments, as is the case in relatively slow working, high sulfite developers, the filamentary silver is indeed forming from slightly smaller grains, potentially increasing the space between aggregations of developed silver, which may lead to less overlap and therefore decreased non-homogeneity as measured by microdensitometry (ie granularity).

    But this is only one aspect of solution physical development. Chemically developed filamentary silver can become thickened by the "plating" of dissolved silver. Or a highly solvent developer can cause the formation of "compact" rather than filamentary silver. Etc. The various combinations and their effects on image structure - particularly traditional acutance, are still not very clear to me. Myths abound, and this extends into tanning/staining developers as well.

    I had a thread going on all this some time ago. It would make for a fascinating discussion with PE etc. And actually it's too bad we couldn't find a way to get people like Silvia Zawadzki and others in on things like this. But they'd probably quickly tire of it.

    All that to say, in order to try to come up with any meaningful experimental conclusions regarding the direct effect of alkalinity on granularity, it seems to me I need to focus on chemical development, meaning eliminate the complications of solvent effects as much as possible.
     
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  17. Alan Johnson

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  18. Rudeofus

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    The question remains why you would bang on that dead horse Metol. If you look at Kodak's and Ilford's more modern commercial B&W developers, they all use Phenidone/Dimezone-S and a secondary developer, which is usually Hydroquinone (HC-110, TMAX, DD-X, Ilfosol, ...) or Ascorbate (Xtol). PE has made it quite clear that the combination of development agents dictates the results (speed, grain, sharpness) you can achieve, so chances are pretty low that you will find a spectacular new developer based on Metol or Metol and a second dev agent.

    Since Sulfite shows no fixing action, I don't think that its grain reducing action comes from Silver Halide grains that are reduced in size. In the early days of photography there were several attempts to first fix away the Silver Halide, then use Silver Nitrate plus developer to create the image from the undissolved latent image centers. The result were abysmal and the resulting film speed was many stops below what could be reached via regular development. I think Haist's books have a chapter about these attempts.

    Another example are monobathes, where Silver Halide is fixed away while the film develops, and again, these are not known to be ultra low grain developers despite the fact that they likely etch away a significant amount of the exposed Silver Halide grains.

    The key to fine grain with solvent developers seems to be the deposition of tiny Silver specks nearby the larger developed Silver grains which sort of blends the density between these Silver grains, thereby reducing density ripple. This reduced density ripple will translate into smaller visible granularity and at the same time reduced sharpness, that's why I tried to compare it to a defocussed enlarger lens.
    I am still not convinced whether solvents are the best way towards small grain. If you look at PC-TEA, there is general agreement that it is a very fine grain developer, yet it is completely free of a solvent. What I personally like to compare grain to is amplifier noise. You start with a few Silver atoms and create whole Silver grains with your developer, which corresponds to a gazillion fold amplification. Different amplifiers (dev agents) will create different noise levels, you can reduce apparent noise by reducing spatial resolution (solvents), and you can increase higher spatial frequencies (e.g. by weak buffering) but will obviously also increase noise at these spatial frequencies. Since the latter two measures tŕade grain for sharpness, I's strictly focus on the first (choice of dev agents) before wasting my effort on trade off optimizations.
     
  19. Michael R 1974

    Michael R 1974 Subscriber

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    Agreed. I'm not trying to re-invent any wheels here, or formulate a developer. Not only for the reasons you cite, but PE has also repeatedly hinted to us that at the point when research at Kodak stopped things were going in new directions we probably wouldn't recognize at all by now. My proposed experiment is strictly an attempt to evaluate and/or learn something (as are all my ventures down technical rat holes).

    Regarding sulfite etching, here I have to disagree with you. Sulfite is a silver solvent and fixer, albeit a fairly poor one in comparison to thiosulfates etc. If we use Haist as a source, the grain etching action of sulfite is documented all over the place. It's in several chapters including The Function of Developer Constituents, Fine Grain Developers, The Fixing Process, etc.

    I can't say much about monobaths other than they are based on the competitive actions of strong developing and strong fixing. Physical development plays a role, but based on my reading of Haist, image structure characteristics are quite complex with all sorts of interesting things about silver mass, covering power, etc.

    I'm not knowledgeable enough when it comes to formulas containing compounds like Ammonia-based alkalis. I've never worked with them. Is this one of Patrick Gainer's things? My understanding is organic Amines do solublize silver halides (at least chloride and bromide).

    But again - I'm trying to get at possible effects of pH exclusive of solvent effects. Hence my choice of a Beutler-type developer as a control.
     
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  20. Rudeofus

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    Kodak may have walked new ways with their research, but Xtol isn't exactly an old formula, so why not base your experiments on the Phenidone-Ascorbate combo? Mark Overton (aka albada) did a great job finding out a formula replicating Xtol, and all your modifications (solvent, alkali, buffering, ...) could start from that formula.

    As I have mentioned, different dev agents and combinations respond differently to pH changes. DD-X/TMAX work at much higher pH than Xtol, and we can safely assume that each has been optimized for best overall performance.

    We both agree that developed Silver grains are not being etched by Sulfite, so the term "grain etching" can only refer to Silver Halide grains. If you dissolve a small part of Silver Halide grains, you create two effects: first, you make these Silver Halide grains a tiny bit smaller. Second, you suddenly have Silver ions in solution that can be physically developed. The term "grain etching", even if applied to Silver Halide grains, suggests to me that the first effect is the dominant one for reducing grain, while I am quite convinced that the second effect is the only one producing visible results.


    Fact is these monobathes contain about as much solvent and etch about as much Silver Halide as you possibly can, but they are still not "costs two stops but gives the finest grain imaginable" kind of developers. This whole theory of solvents and grain must be flawed.

    TEA is a tertiary amine which has no Silver Halide solvent power to speak off. It is an alkali that can dissolve a range of organic compounds and mixes freely with water, which makes it great for developer concentrates. Water free concentrates is what the Ascorbate developer crowd yearned for, because it kept their Ascorbate stable without special, hard to get sequestering agents. It gives pH values around 9, which is a bit lower than Carbonate/Metaborate and therefore quite suitable for developers which want the lower pH.
     
  21. yurisrey

    yurisrey Member

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    great thread, cleared up a few grey areas I had in my own notes.
     
  22. Michael R 1974

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    I guess the reason I'm not basing this particular experiment on Phenidone-Ascorbate is I like to isolate things as much as possible as a starting point, to limit/eliminate as many variables as possible. We all agree the totality of any scientifically balanced developer formula determines its characteristics, and it is nearly always problematic to generalize or extrapolate, even based on a well constructed test. So I figured looking at the effect of pH on a "simple" Metol formula is as good a test as any other. I see what you're getting at though, and it is a good point: Since we likely can't generalize regarding the pH effect on granularity, even sound experimental results with a Metol developer may not be applicable to the more current superadditive formulations we commonly use, such as XTOL, and so the results would be of limited value. I can't really argue there. Then again, I'm not looking to formulate a developer (my ultra low contrast/high speed experiments aside - although those experiments did lead to me wanting to explore this pH question). I'm quite sure I can't come up with anything better than XTOL for general purpose work.

    Well, yes and no. DD-X and TMax both work at pH~8.5 (same as D-76) where XTOL is at 8.2. But I agree the combinations, agents present and relative concentrations are all variables in play when pH is adjusted. And in an experiment such as the one I propose, unless characteristic curves for a given film can be duplicated, not much can be concluded.


    It is possible. The silver halide grains are slightly smaller, but then dissolved silver is "replated" onto the chemically developed filaments, thickening them. In cases where solution physical development is more dominant, the entire structure of the resulting metallic silver can be different (commonly referred to as "compact" vs filamentary or thickened filamentary). We'd need some more input here. One wonders then, in the case of Microdol-X, if the (assumed to be present) anti-silvering/plating agent resulted in it being slightly grainier than Microdol...


    Perhaps. I certainly think it is somewhat flawed where sharpness is concerned. Actually in the case of sharpness the flaws are less in the theory and more in the misinterpretations of the theory and other misimpressions which have formed the conventional wisdom of photographers for so long.

    Yeah, this is where I'm less knowledgeable. Amines in general actually. I only know the basics of these compounds and how they are used, particularly in concentrates.
     
  23. Rudeofus

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    For Metol you need Sulfite in order to eliminate oxidized Metol from the reaction, so you have a lot more complexity to start with.

    If you look at PC-TEA, that's about as simple as it gets. For your tests you don't need to make a concentrate, just mix the compounds as given by the working solution recipe. Three components, all with very well defined purposes (no multifunction compound like Sulfite), and pH trivially adjustable with NaOH and Acetic Acid. You can add Carbonate/Bicarbonate to see the effect of stronger buffering.

    PE mentioned at one time that the mystery compound added to turn Microdol into Microdol-X is a compound that also reduces the yellow appearance of the negative image. Since we know that warm tones come from smaller grains, there is good reason to believe that Microdol-X produces slightly coarser grain. Warning: I have never used Microdol or Microdol-X, so I have no experimental data to back up my claim.

    About the replated Silver: If you take off Silver ions from the Silver Halide grains, then replate it onto the developed Silver grains, I don't see how this would reduce visible granularity. If replating Silver would increase density without increasing granularity, then underdevelopment plus intensifier would give better results than proper development. BTW this was tried early on in the history of photography but never seemed to give improved results.
    I have another argument against the theory with replated silver: there should be plenty of dissolved Silver ions, ready for replating, near a section with a strong contrast feature. If replating takes place in sizable quantity, such solvents would boost sharpness and create strong Mackie lines. To my best knowledge, they don't.
     
  24. Michael R 1974

    Michael R 1974 Subscriber

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    I'll have to consider this PC-TEA idea. I'm also curious as to how this formula, with no solvent effects at all, actually produces fine grain. One of the issues I've always had with Gainer's formulas is I can't recall ever seeing any sort of objective evidence for anything. The results always seemed more or less anecdotal. Then again I haven't reviewed every one of his experiments so I may be overstating/understating the case. By the way, what is the working pH of PC-TEA?

    On the Metol side, I was going to try using a very small amount of sulfite, something like 1-2g, maximum 5g in order to limit solvent effects as much as possible, and perhaps use a decent amount of Metol. Something like one of the "AH" "sharpness" formulas in the Altman/Henn study. Need to think about it some more.


    I never used Microdol or Microdol-X either. I've done a lot of work with Perceptol in the past, which is probably very similar if not identical to Microdol, but not Microdol-X.

    Regarding replated silver, I agree, or rather I should say I don't see how this would reduce granularity. So then I'm at somewhat of a loss to explain the fine-grain effects of solvent developers such as D-76 etc. In cases such as these where filamentary silver is produced by chemical development, but there is also solvent action, what specific aspect of the solvent action leads to lower granularity? It seems perhaps a little more straight forward in Microdol or even PPD-based developers where the resulting metallic silver, rather than being filamentary in structure, is more "spherical" and compact - though apparently with lower covering power. What about DK-20, which included a more powerful silver solvent (thiocyanate) in addition to sulfite? How did that produce extra fine grain?

    And then this brings me back to the possible effects of pH. Microdol, D25, and the old PPD formulas were low pH, solvent formulas. But monobaths, also highly solvent, work at high pH values, and do not form "compact" silver. I believe it is usually of the thickened filamentary type. But there are interesting issues in the case of monobaths with respect to the replated silver adding mass but not increasing covering power (I think). I'd have to go back to Haist's books and re-check, but it is complex. I also remember reading somewhere that pronounced edge effects can occur in monobath development, although I'd have to find the source. It may have been something from Troop in the FDC but I'd have to check.
     
  25. Alan Johnson

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    At one time PC-TEA was tried by quite a few users.I found the finest grain was obtained using it diluted 1:100 and developing for about 20min,but it was not as fine grained as Xtol (no solvent effect) nor did it give such high film EI (no sulfite to uncover latent image specs?)Typically for Xtol EI=100, PC-TEA EI=64,Beutler EI>100.

    Crawley BJP Jan 6 1961 tested the effect of sulfite with metol:
    "...below 5g/L film speed begins to drop; this is interesting, as it can be traced to the solvent effect of sodium sulphite, but this time to its lack...
    By the time the concentration is lowered to 2.5 gm/litre,film speed drops, from the 1 stop practical increase over D-76... at 5gm/litre sodium sulphite, down to normal.
    etc etc.."
     
  26. Rudeofus

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    Pat Gainer did his tests at the worst possible time in history: skilled photographers were defecting to digital left and right, but at the same time he did not enjoy the availability of cheap electronic scales and pH meters and a nice, searchable patent archive. In all his postings and articles I see no reference that he ever did a pH measurement of his developers. We are really spoiled these days and should be amazed what Pat Gainer accomplished with the means he had, and grateful that he published his results so freely.

    I don't know, but I would assume it is somewhere between 8 and 8.3, like all other high performance Ascorbate developers.

    As I have mentioned previously, Metol needs Sulfite to be active at all. You will see very different behavior if you reduce Sulfite to these low levels. That's the great thing about Ascorbic Acid, that it restores oxidized Phenidone yet needs no Sulfite to work. It decouples many of the reactions going on in other developers, and it gives you a high performance developer out of the box. You can add Sulfite if you want (Xtol, DS-10 do this) but you can leave it out completely if you feel like experimenting.

    My personal impression is that different development agents produce different speed, sharpness and granularity out of the box. With extra solvents and different pH/buffering you can trade some of these three properties for the other ones, but you can not create and should not expect miracles. This leaves you with two options: either find novel dev agents that haven't been beaten to death in the last hundred years, or base your experiment on the best dev agents you know of, and find a different balance between speed, grain and sharpness that suits your need better than Xtol.