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  1. #21

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    Quote Originally Posted by Rudeofus View Post
    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.
    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.

    Quote Originally Posted by Rudeofus View Post
    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.
    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.


    Quote Originally Posted by Rudeofus View Post
    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.
    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...


    Quote Originally Posted by Rudeofus View Post
    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..
    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.

    Quote Originally Posted by Rudeofus View Post
    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.
    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.

  2. #22
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    Quote Originally Posted by Michael R 1974 View Post
    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.
    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.

    Quote Originally Posted by Michael R 1974 View Post
    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...
    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.
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  3. #23

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    Quote Originally Posted by Rudeofus View Post
    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.
    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.


    Quote Originally Posted by Rudeofus View Post
    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.
    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.

  4. #24

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    Quote Originally Posted by Michael R 1974 View Post
    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.



    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.."

  5. #25
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    Quote Originally Posted by Michael R 1974 View Post
    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.
    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.

    Quote Originally Posted by Michael R 1974 View Post
    By the way, what is the working pH of PC-TEA?
    I don't know, but I would assume it is somewhere between 8 and 8.3, like all other high performance Ascorbate developers.

    Quote Originally Posted by Michael R 1974 View Post
    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.
    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.
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  6. #26

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    Quote Originally Posted by Alan Johnson View Post
    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.."
    This is true one of the benefits of some amount of etching of the silver halide grains by sulfite is to uncover some latent image sites which might otherwise be left undeveloped by "pure surface" development. The effect has been cited as one of the reasons - apparently unexpectedly at the time it was invented - D-76 gives full film speed. However I've never been clear even broadly speaking, on the amount of sulfite required (although again pH, development time etc. are variables here). Reading some sources you're left with the impression it would have to be considerably higher than 5g/l. But again this would depend on other factors.

    Luckily my investigation/experiment is independent of film speed (as long as the two developers produce the same speed and curve).

  7. #27
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    My question in the past,

    http://www.apug.org/forums/forum47/1...evelopers.html

    is slowly answered here. Though I am not a chemist, the last post about D-76 giving full film speed is quite interesting.

    May I know where I can read more about it?
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  8. #28

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    Quote Originally Posted by Rudeofus View Post
    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.
    Just to clarify, Metol, a tiny amount of sulfite, and different alkalis. I wouldn't be relying on the sulfite to activate the Metol. Although now that you mention it, perhaps another interesting experiment (if there is enough Metol, it can be active even at a neutral pH).


    Quote Originally Posted by Rudeofus View Post
    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.
    Can you expand a little more on your reasoning regarding the relative granularity of different agents out of the box? In an earlier post I mentioned how according to some microscopic studies, active agents such as Metol produce silver that leaves virtually no remnant of the original shape of the silver halide grain, while an agent such as HQ tends to leave the original shape of the grain relatively intact (although obviously with rough edges due to the nature of the protruding silver filaments). Although it would seem to me pH plays a role here, I can't think of how these differences would result in differences in granularity.

    Don't worry I'm not expecting any miracles. Far from it. It's just some experimentation for learning. For normal purposes, I can't imagine there is anything much better than XTOL to be discovered without radical new compounds/approaches. For special purposes, perhaps things can be optimized for specific characteristics (for example, I think we were off to a fairly good start on those ultra low contrast/high speed P-C/P-"X" formulas I was experimenting with in the other thread.

  9. #29

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    Quote Originally Posted by Michael R 1974 View Post
    By the way, what is the working pH of PC-TEA?
    1:50 pH=9.07, 1:100 pH=9.01 (Sandy King):
    http://photo.net/black-and-white-pho...08B3p?start=10

    I found in practice with dilution 1:100 the pH falls from this during development towards ~8
    It still does not match Xtol for EI or grain.

  10. #30
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    Quote Originally Posted by Alan Johnson View Post
    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.
    The definition of film speed assumes that the characteristic curve right of the toe region is a straight line until the shoulder region is reached. If you use a compensating developer, you walk away from this straight line intentionally, which means you can develop much longer and still report a low contrast index. This allows you to claim a boost in film speed, but you have to live with a concave characteristic curve. If that's the characteristic curve you are after, go for it, but not all subjects benefit from such a curve. That was actually the great thing about Michael's low contrast developer: he reached good film speed yet had a perfectly straight characteristic curve.

    One more thing about PC-TEA: I don't think it was optimized as much as Xtol. I already mentioned Pat Gainer's very limited access to lab equipment, chances are he never played with mixing ratios of TEA, DEA and PG (Michael, that's your chance ). One more thing: Pat Gainer also designed PC-Glycol, where he recommended addition of Sulfite to the working solution. AFAIK he made no such recommendation for PC-TEA, which tells me that PC-TEA does not benefit much from Sulfite. He would have most certainly noticed a factor two speed gain with such a simple modification. Several folks played with Sulfite additions to all kinds of prepackaged developers back then, with no real break through success ever reported.

    Quote Originally Posted by Alan Johnson View Post
    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.."
    Was Crawley aware that Sulfite is needed to get oxidized Metol out of the way?

    BTW one thing that never ceases to amaze is the common claim that D-76 gives full speed, followed by a long list of developers that supposedly give at least one stop better speed than D-76. The answer is: D-76 does not give full speed, since Microphen and Xtol mop the floor with D-76, speedwise. IIRC, the definition of ISO film speed was changed after Phenidone/Dimezone-S based developers became common.
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