Stand Developer Concentrations

Discussion in 'B&W: Film, Paper, Chemistry' started by Kirk Keyes, Aug 20, 2005.

  1. Kirk Keyes

    Kirk Keyes Member

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    All this recent talk about stand developing has inspired me to ask a longstanding question that I've had about this technique - I notice that when making up the developer using a 2 part developer like Pyrocat-HD, practitioners seem to maintain the ratio of the A & B parts fairly close to what is used in the "normal", non-stand application. I often see suggestions for 1+1+200 or 1+1+250, or sometimes like Steve Sherman's View Camera article which mentions 1.5+1+233. All these developer concentrations require relatively long development times.

    So what I'm wondering, is has any one tried dilutions where the B part is at a higher conc than the A part, and still in proportions that are similar to the original formulation (1+1+100 or sometimes 1+2+100)?

    I'm curious to find out what happens when the pH of the developer remains similar to what it is in normal dilutions, or perhaps even higher? Using the developer at a higher pH should help push the kinetic balance of the development process, and this should result in shorter development times. But by keeping the A part limited, it should promote the exhaustion of the developer in the highlights.

    So has anyone tried dilutions like 1+4+200 maybe even 1+6+200?

    Kirk - www.keyesphoto.com
     
  2. gainer

    gainer Subscriber

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    Increasing the pH should also increase the initial rate in both shadow and highlight. From there it's a race to see whether the shadows develop faster. Maybe it's a little like asking if a glass is half full or half empty. If anyone knows the answer, it is Sandy King. If no one knows, an experiment is called for.
     
  3. Kirk Keyes

    Kirk Keyes Member

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    I don't get the water glass analogy, Patrick, but I agree that the initial rate, and other development rates should increase at the higher pH. And granted, with a well buffered developer the pH may not change all that much, but it should increase some.

    And since the development is being pushed along at a faster development rate from the higher pH, that leaves us to the diffusion rate of the chemicals in and out of the film. So I would suspect that this approach may give higher edge effects than the weaker pH versions of the same developer - the exhaustion rate of the developing agents will increase, while the diffusion rate of these agents (and their by-products) should be very close to the same rate as at lower pH levels.

    Perhaps the diffusion rate will be the limiting factor in this type of development approach. But then the higher pH solutions may benefit from more frequent agitation than what is used with the "traditional stand" technique and therefore help lower the development times.

    Maybe this would lead to less "standing" around in the darkroom? Talk about kinetics!
     
  4. Photo Engineer

    Photo Engineer Subscriber

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    Kirk, I'm rather amused at this thread.

    I can understand criticism of using a microdensitometer as being to expensive and 'technical' for common usage in the other thread, but here you are dragging pH into it.

    Now, even with pH meters being so inexpensive, how many times do we see people discussing the pH of their developer, or adjusting the pH in their experiments to insure batch to batch uniformity? Seldom, right?

    I think that your direction has merit, but as for quantifying it or getting repeatable results it will not happen until the pH and buffer capacity are documented for all of the conditions. This will probably draw a lot of criticism, I'm sure, but some of the effects of stand and dilute developers are due to halide edge effects, and others are due to pH effects (buffer exhaustion) and no one has gone to the trouble of distinguishing between them, even though they do different things and act different ways.

    In the other thread, you propose standards, but standards imply measurment and numeric values and this was negatively viewed for the most part.

    I think your suggestions here and earlier have great merit. Keep it up. Non illegitemati carborundum (just in case they try).

    PE
     
  5. sanking

    sanking Member

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    Kirk,

    My experience is that the opposite is true, i.e. for stand dilution with long development times it is better to slightly incrase the proportion of A to B. Having more A in the working solution seems to slow down the rate of exhaustion and results in less general stain. If one increases the prorportion of B to A, the result (at least my result) is more general stain, even with slightly shorter times of develoment.

    This is my experience, though the observations are based on just a few, and perhaps incomplete, direct tests. It may well be that more extensive testing will prove me wrong.

    Sandy
     
  6. sanking

    sanking Member

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    I can not speak to the practice of others but I have always used pH meters in my work in comparing developers.

    I don't know about the relationship between dilution and pH with other developers sometimes used in stand developing, such as HC-110 and Rodian, but I do know it for Pyrocat-HD. This is virtually no difference in pH in Pyrocat-HD solutions ranging from 1:1:100 to 1:1:400.

    Sandy
     
  7. Tom Hoskinson

    Tom Hoskinson Member

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    I don't mention pH and the use of my pH meter in every thread. Then again, I don't mention my microdensitometer either...
     
  8. Photo Engineer

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    Sandy, the buffer capacity of a solution can decrease with dilution while the pH can stay the same. This is due to the buffering effect itself. As buffer capacity decreases, the production of hydrogen ion becomes gradually more and more significant in the overall reaction, and begins to have its own effect similar to bromide in edge effects. It does not 'drag' in the classical sense of 'bromide drag' due to the lighter nature of hydrogen ion, but rather it tends to diffuse further in all directions.

    Tom, I would love to see some data from your microdensitometer. Of course, to use it properly, you do have a microsensitometer, right? Oh, I suppose you also have a source of soft x-rays for it so you can separate out edge effects and turbidity.

    I, of course, have all of the above powered by a small 1.21 gigawatt Tokamak in the basement. It was given to me by a Vorlon named Kosh, but then aren't they all?

    PE
     
  9. gainer

    gainer Subscriber

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    It's another way of saying that maybe it half a gross of one and six dozen of the other.
     
  10. gainer

    gainer Subscriber

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    Does "carrying coal to Newcastle" mean anything to you?
     
  11. gainer

    gainer Subscriber

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    If you want to make use of pH change to reduce local development rate, consider ascorbate developers, which produce acidic byproducts of development.
     
  12. gainer

    gainer Subscriber

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    And don't say anything about lack of stain. I, and even you, Photo Engineer, can produce a stained image from an unstained one by bleaching in a rehalogenating bleach and redeveloping in any staining developer. You can have the color of PMK, or Pyrocat, or even hydroquinone.
     
  13. Photo Engineer

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    Patrick, ALL commonly used developing agents produce acidic byproducts. Even I know that. That is why buffer capacity as well as pH are important factors in most all developers. They all change local pH, not just ascorbic acid.

    I grew up not far from Newcastle Pa, and heard that old expression a lot.

    PE
     
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  15. Tom Hoskinson

    Tom Hoskinson Member

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    It's published.

    Let's see yours. Does your microsensitometer run on psi energy from Aldeberan?
     
  16. sanking

    sanking Member

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    PE,

    OK, so how do you measure the buffer capacity of a solution, as distinct from mesuring its pH.


    Sandy
     
  17. Photo Engineer

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    Sandy, buffer capacity is defined as the resistance of a solution to change in pH by addition of acid or base. For example, water is said to have a buffer capacity of zero, and a drop of acid or base will cause a wide swing in pH.

    A solution of Sodium Carbonate at 1 g/l at pH 10 has low buffer capacity, and a solution of Sodium Carbonate at 100 g/l at pH 10 has very high buffer capacity. Addition of one drop of acid to one will cause less change than one drop of acid to the other. The actual capacity is measured by using the pKa of the buffer in question and the concentration. It is usually derived by titrating the solution with acid or base and plotting pH vs the equivalents of base or acid added. The slope of the graph falls to about zero at the maximum buffer point, and the length of the flat portion of the curve is the indicator of the buffer capacity.


    Mixed salts are better than single salts. Therefore, a solution of Sodium Carbonate and Sodium Bicarbonate is better buffered than just one or the other.

    Sodium Acetate and Acetic Acid make a good buffer pair at pH 4.5 and that is why they are used often together in acid fix solutions. They buffer well up to about 6.5 and are often used that high.

    PE
     
  18. sanking

    sanking Member

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    PE,

    OK, but what is the relevance of this, for this discussion, to a developer that when mixed has a given pH, and at the end of devleoment has the same pH.

    Based on one of your previous messages I assume that it has something to do with the pH in border areas of heavy and light densitities where the developer is exhausting more than in the general solution. But if so, specifically how does this relate to a developer that begins with a general solution of around pH 10.9 and maintains that pH throughout the development.


    Sandy
     
    Last edited by a moderator: Aug 20, 2005
  19. gainer

    gainer Subscriber

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    Actually, the expression originally referred to Newcastle in the British Isles. I was referring to your lecturing Sandy King about pH.
     
  20. gainer

    gainer Subscriber

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    Not as much as the ascorbates. A product of development by ascorbic acid is the dehydroascorbic acid whiich is more acidic than ascorbic acid, as well as the hydrogen bromide, etc.
     
  21. gainer

    gainer Subscriber

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    I am not the only one who holds that the products of development by ascorbic acid are more acidic than those of development by hydroquinone and its brothers. See the article by Ryuji Suzuki at his silvergrain.org website
    about ascorbate developers.

    I quote here a portion:

    "The oxidation products of hydroquinone (ones that are exhausted after developing reaction) is alkaline. This may accelerate development in the area
    surrounding areas of intense development reaction. On the other hand, the
    oxidation products of ascorbates are acids, potentially inhibiting development in areas nearby the site of intense reaction. This means that ascorbates are more desirable when adjacency effect and compensation effect are sought."
     
  22. sanking

    sanking Member

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    To be precise.

    Carrying coals to Newcastle.

    1. To do something that is obviously superfluous;
    2. Used to describe a foolhardy or pointless action.
    3. To describe or add to something for which an excess already exists.

    Logic of the expression. Newcastle was historically an area where coal was mined in great abundance. It woul therefore have been a ridiculous and pointles action to carry coals to that place.

    Rough equivalents in other languages.

    French Porter de l'eau à la rivière Water to the river
    Portuguese Vender mel ao colmeiro Sell honey to a beekeeper
    Spanish Echar agua al mar Throw water into the sea
     
  23. fhovie

    fhovie Subscriber

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    Now I am confused - It seems in a previous post - Sandy quoted Hutchings as stating that ascorbic acid as well as phenidone would create very low accutance/adjacent effects. Now here Patrick has quoted Suzuki stating that accutance is greater with ascorbic acid. I notice that accutance is pretty good with XTOL and not very good with PC TEA. I had thought that it was the sulfite in the mixture that helped create the accutance. TEA may be a good buffer and stableizer but not a silver solvent needed to cause silver grains to erode and redeposit on the edges - as I have read from Anchell. What is the truth of this? anyone?
     
  24. john_s

    john_s Subscriber

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    So maybe Hypercat and Pyrocat-HD are opposite in their behaviour when diluted for stand/minimal agitation development. The hydroxide is so poorly* buffered that increasing the ratio of B/A might be needed to keep the developer going, but in the case of Pyrocat-HD, the carbonate is much better buffered, and doesn't need the ratio of B/A increased.

    This is merely armchair conjecture. I have used Pyrocat-HD a lot at 100+0.6+0.6 with minimal agitation for about 18 minutes and it still has plenty of power left to increase contrast if development is extended. (I use 500mL for one 120 roll)

    * by using the word "poorly" I am not being derogatory. I understand the benefit of local developer exhaustion (edge effects).
     
  25. Kirk Keyes

    Kirk Keyes Member

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    Sandy - I did expect this to be part of the observations with this approach - a higher base+fog or stain level.

    But I now see that I failed to mention a very important part of my question in the original post - what happens to the edge effects. (Sorry about that... I didn't mean to send people off on a wild goose chase.)

    I take it this is why Patrick was talking about glasses of water and other such metaphorical euphamisms. I suspect he thought I was only concerned with the over all H&D curve of the prcessed film. I was really interested in using this technique to get increased adjacency or edge effects - the microdensity effects.

    So yes, higher stain/fog would be expected due to the developer being more active, but do the adjacency effects benefit from this approach?

    I can see that one may reject the results from initial tests of these dilutions because of the higher stain, but if adjacency effects benefit, then the increase in fog/stain may be worth it.

    Kirk - www.keyesphoto.com
     
  26. Kirk Keyes

    Kirk Keyes Member

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    Ron - glad to brigthen your day!

    Yeah - I wish there was a reasonable inexpensive approach to the microdensity issue - I would certainly spend several hundred dollars (probably more over time!) to get a system that could give me this type of info. Simply because it would allow my film/developer testing to go to the next level of information.

    And that is a good point about using a pH meter to check formulation consisitency. I have never done it other than on a very occasional basis. I have titrated a few things - such as when I was attempting to reverse engineer Xtol back when it came out.

    But yes - excellent point on the buffering capacity being just as important as pH. My proposed approach would certainly greatly increase the buffering capacity (alkalinity) of a developer. And as Sandy pointed out, diluting Pyrocat doesn't change the pH significantly with dilutions from 1+1+100 to 1+1+400. But the bufering capacity is going to be 1/4th as much in the second dilution. And in the dilutions I suggested it would be 4 or more times greater.

    Side note: I'm always amused when people say that their tap water has a pH of such and such, and that's why it is unsuitable for some particular application. Without knowing the buffering capacity, i.e. the alkalinity or less frequently the acidity of that water, they really can't make any such claims. There's a whole lot more to water chemistry than just pH.