A fortified TCB developer for long shelf-life

Discussion in 'B&W: Film, Paper, Chemistry' started by Tronds, Dec 1, 2011.

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  1. Tronds

    Tronds Member

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    Developers containing ascorbic acid as antioxidant may well have long shelf-life, but when used similar to D76, they loose their power rather quickly due to oxydation of the ascorbic acid from the air introduced into the developer when used.

    The solution to this may be my version of the TCB-developer.

    More information and picture at A TCB developer with long life.
     
  2. Gerald C Koch

    Gerald C Koch Member

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    I don't understand your post. First you talk about developers using ascorbic acid as an antioxidant. Then you state that such developers loose their power rather quickly. The lose of "power" would be due to lose of developing agent due to oxidation not to lose of antioxidant. The pH of the TCB developer is >9 and at this pH the ascorbate ion is an active developing agent. If by "used similar to D-76" you mean replenishment then Kodak states that Xtol (an ascorbate developer) will keep indefinitely as long as it is replenished regularly.

    Since TCB contains no chelating agent to prevent Fenton oxidation its keeping properties will be poor as compared to Xtol and other formulas that do use a chelating agent.
     
    Last edited by a moderator: Dec 2, 2011
  3. albada

    albada Member

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    Thank you for posting this interesting formula, which I copied below:

    500 ml water.
    8 g Sodium carbonate. (Soda)
    10 g Ascorbic acid. pH at this moment is 9.6
    80 g Sodium sulfite
    10 ml Parodinal
    20 g borax.
    Water to 1000 ml. pH at this moment is 9.15

    I have one question: Why does the formula have both Sodium carbonate and Borax? By adding more carbonate, you can omit the Borax. Does the Borax improve the image quality?

    Cheers,

    Mark Overton
     
  4. Tronds

    Tronds Member

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    Well, Go head and do a test run if you don't understand this.

    The ascorbic acid is converted to ascorbate.
    When using ascorbic acid both as an antioxydant and a developer agent, it works well until you start using and reusing the developer. It will be oxydated by aerial oxydation.
    When enough of the ascrobate is oxydated, it will loose it's powers. Since phenidone forms a superadditive pair with ascorbate, the loss of ascorbate will kill the developer.
    This has been tested and I know for sure it will stop working after very short time.

    By using it as D76 I mean using it as D76, not as XTOL.
    Replenishment is another issue. If this developer is replenisshed, it will keep forever.
     
  5. Tronds

    Tronds Member

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    The reason for using sodium carbonate is that you have to convert ascorbic acid to ascorbate. The pH required for this conversion is above the pH of borax.
    This is done when adding the ingredients in the listed order.

    Adding more carbonate will make the developer more active, but you will get more grain.
    Keeping pH as low as possible helps keeping the fine grain properties of ascorbic developers. The pH must be over 9.0, so using borax as buffer is great since the pH will be in the range 9.1 - 9.2.
    The parodinal amount is 1:100 in this developer and not enough to develop a film in 10 minutes alone, so the ascorbate is doing a great job.
    The p-aminophenol in the parodinal does help the shapness. This is a well known property of the Rodinal developer. Combining fine grain and sharpness isn't easy, but this developer does this.
     
  6. Alan Johnson

    Alan Johnson Subscriber

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    Your brew contains more ascorbate and sulfite than some Xtol-Rodinal mixes that have been tried,but probably has similar development chemistry.For example:

    Xtol(1+0).........200ml
    Rodinal...............6ml
    Water to..........600ml
    http://www.apug.org/forums/forum37/58171-acutance-6.html

    It does not appear to be known for sure if the increase in sharpness over Xtol (1+2) is the result of increased pH or some chemical effect of p-aminophenol.
     
  7. michael_r

    michael_r Subscriber

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    I would like to see data supporting this. Rodinal is a little sharper than XTOL (and Rodinal's sharpness is generally overstated) because it is a non-solvent developer, not because of its developing agent. Second, combining high sharpness and fine grain is not really possible, unless you develop to a low contrast index, which works quite well with XTOL 1+3 incidentally. I think formulating a developer with a better combination of sharpness and graininess than XTOL would be pretty difficult.
     
  8. Tronds

    Tronds Member

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    You don't have to try this if you don't want to. It's your call.
    Besides that, I never ment this to be another XTOL clone.

    To me it is about enough that it gives fine grain and good sharpness in a developer that gives predictable results and is easy to mix and has low cost.

    Try it if you want. If you don't want to try it, I don't care. It's your problem.
     
  9. Tronds

    Tronds Member

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    In the testing process I have tried several different mixes with and without the rodinal addition. PCB, PCS, combinations of them etc.
    The TCB version IS sharper. p-aminophenol is known to develop sharp images, so in my opinion it is the key element here.

    I may be wrong about this, but do some tests and decide for yourself.
     
  10. Alan Johnson

    Alan Johnson Subscriber

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    Actually metol is the preferred agent for this purpose. Metol and phenidone (in FX-39) both come above p-aminophenol (Rodinal) in the tables given on p55 of the Film Developing Cookbook.

    I don't think others will work to verify your claims if you present no evidence.
    Did you compare sharpness with and without p-aminophenol at the same pH?
     
  11. albada

    albada Member

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    Here is a PC-type developer called PCB which only uses Borax as its alkali: www.apug.org/forums/archive/index.php/t-91805.html
    It consists of 19g borax + 6g ascorbic acid + 0.15g phenidone in 1L water.
    Therefore, Borax alone is sufficient, so carbonate is not needed.
    I suggest that you try omitting the carbonate from your formula, and adjust the pH another way, perhaps with Sodium metaborate or more Borax. It may work well, and maybe with less grain.

    But here's another question: You can increase the carbonate and then omit the borax, keeping the same pH. How would this affect image-quality? I guess that grain will be worse, but I'm not sure.

    Mark Overton
     
  12. MichaelMadio

    MichaelMadio Member

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    You can probably do away with or use less of the sodium carbonate as there's already enough borax to neutralize the ascorbic acid. To neutralize 10g of ascorbic acid (0.057 moles) you can use the following:

    borax = 10.83g
    sodium carbonate = 6.02g
    sodium bicarbonate = 4.77g
    sodium hydroxide = 2.27g
     
  13. Photo Engineer

    Photo Engineer Subscriber

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    I am not aware of any great degree of synergy between phenidone and ascorbate. Certainly none like we have between Metol and HQ. As for the claims here, it seems more like hand waving or smoke and mirrors. For example, the statement that Carbonate is needed to convert Ascorbic Acid to Ascorbate, and then you add Borax is quite contradictory.

    Gerald has it right! You need to suppress Fenton oxidation (although we refer to it mainly as involving just Iron salts), which is what is effectively the real problem with Ascorbate developers.

    PE
     
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  15. Tronds

    Tronds Member

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    Increase carbonate and omit borax to get the pH where borax is a perfect buffer? (9.1 -9.2)
    Why? at pH 9.1 to 9.2 I can add a lot of borax and the ph won't change. The acid products created during development will not change the pH when a lot of borax is used.
    Why shouls I increase carbonate then?
    The best is to get rid of the carbonate alltogether.
    The reason for having it there is to convert ascorbic acid to ascorbate in a way that ensures me that all of it is really converted. There is no other reason for having the carbonate there.
    I am not completely satisfied with the conversion of ascorbic acid to ascorbate in a pure borax solution. You will get ascorbate, but how much? How fast?
    Using carbonate works great for this purpose.
    The amount of carbonate doesn't affect the pH of the finished developer, so I don't use it to adjust pH.
    Please do some tests and you will discovder that this is true.
     
  16. Tronds

    Tronds Member

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    You are probably right. I just want to make sure that I get ascorbate from the ascorbic acid.

    It doesn't matter when it comes to cost. Carbonate is dirt cheap.
    It doesn't matter when it comes to pH either since the large amount of borax controls the pH.
     
  17. john_s

    john_s Subscriber

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    Why does this developer have long shelf-life?
     
  18. Tronds

    Tronds Member

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    You don't know that phenidone and ascorbate forms a superadditive pair?
    Yeah! You are a great photo engineer. NOT!

    Besides that, the TCB-developer we are discussing here doesn't have any phenidone.
    You talk about Fenton. What is that? A friend? A foe?
    Can you please stick to discussing what this developer does and what it contains.
    All your talk about Fenton seems more like hand waving or smoke and mirrors.

    Oxydation of Fenton (whatever or whoever that is) isn't the problem with ascorbate developers. The problem with ascorbate developers is oxydation of the ascorbate. When the ascorbate has oxydated, it can't protect other developing agents anymore, and since it doesn't woirk as intended anymore, the activity of the developer goes down.

    If ypu want to test this with phenidone and ascorbate, just mix a PC-developer and omit the ascorbate. Then you have a developer just like a PC-develper with oxydated and useless ascorbate. Use a carbonate alkali that places the pH at about 11.2.

    Hint: 0.15g phenidone per 1000ml.

    Check if you can get a ISO-100 B&W film developed in 6.5 minutes @20C with that.

    If you get good development without the ascorbate I will shut up and never dispute this.
    Hint: You won't!

    Add 6g ascorbic acid and do a new test.
    This time you will get good development i 6.5 minutes@20C.

    Do a new test. This time with 6g ascorbic acid in the pH 11.2 carbonate solution.
    Check if you can get a ISO-100 B&W film developed in 6.5 minutes @20C with that.
    Hint: You won't!

    But as I initially said, This TCB developer DOESN'T contain any phenidone or your friend "Fenton", so when and how fast phenidone are oxydated isn't of ANY interest with this developer.

    I suppose that you are trying to twist the discussion over to that theme because you haven't anything to discuss about this developer.

    That is hand waving or smoke and mirrors to me.
     
  19. Tronds

    Tronds Member

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    Who is Fenton?
    I don't care if Fenton is oxydized, because he isn't in any way connected with this developer.

    Tylenol, ascorbate and alkali.
    NO "FENTON" whoever or whatever that is.

    I have read a lot of books about developers. I also has worked in a photo finishing lab for aan extended time.

    I have NEVER heard or read the word Fenton in any realation to developers.
    Stick to correct or well-known names on the chemicals involved.

    Your statement about Fenton is just a method of twisting the thread away from the original issue and over to a issue you want to discuss.
    That is the way you want to "win discussions" on the net.
    Smoke screen?

    Start your own thread about "Fenton" if you want to discuss him.
     
    Last edited by a moderator: Dec 2, 2011
  20. albada

    albada Member

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    In this article, http://unblinkingeye.com/Articles/Synergism/synergism.html , Patrick Gainer has a graph of the synergy between phenidone and ascorbate, based on the ratio of ascorbate-to-phenidone. He found that the curve began flattening at around 40:1, and was quite flat at 80:1.
    Any comments on his work?
    I'm also aware that phenidone doesn't need a partner for development, as in POTA.

    Mark Overton
     
  21. Lukas_87

    Lukas_87 Member

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    OXIDATION, for Christ's sake!
     
  22. Tronds

    Tronds Member

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    Meaning what?
    Interesting statement BTW.
     
  23. Tronds

    Tronds Member

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    Soduim Sulfite.
     
  24. Photo Engineer

    Photo Engineer Subscriber

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    I will answer these comments one at a time.

    1. In post #4 synergy with phenidone and AA is mentioned. I said it was not on the order of the synergy between HQ and Metol. Here is what Gainer says:

    "Phenidone is often described as the primary agent in developers like the one tested here. The secondary agent is said to regenerate oxidized phenidone to its original state. In fact, the ascorbic acid is a scavenger of anything that might be, at least in old-fashioned terms, a free radical. Oxygen in water solution is such, as is chlorine used as disinfectant. Halogen atoms set free from silver halides by photolysis or by phenidone are taken by ascorbate and converted to hydrobromic acid and dehydroascorbic acid. Phenidone is not lost in this process, but ascorbate is. The experiments presented here have shown that adding ascorbate to a phenidone-ascorbate developer above the amount that can be activated by the phenidone content will cause little change in developer activity. The excess serves as a preservative and as a reserve."

    There is no synergy really mentioned here nor shown in the article to my satisfaction. He does, however, make a good case for AA being an effective antioxidant. So, I answered a specific comment and based it on the above comments by Gainer.

    2. Fenton is the well known iron - peroxide caused decomposition of reductants in solution, and the basic cause of instability of AA developers in the opinion of some. It is said to be offset by salicylic Acid and other sequestering agents added to developers. See the many threads on this subject here.

    3, The correct spelling is OXIDATION!

    4. I am a chemist and so is Gerald Koch.

    PE
     
  25. Tronds

    Tronds Member

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    Thanks for correcting me on that.
    Very important.
    Enligsh (US or UK variant) isn't my first language, so you have to live with that.

    If you can't stand a few spelling errors, please stop reading my threads/comments.

    You have now proved that you can safely be ignored.
    Welcome to my ignore list!
     
  26. mwdake

    mwdake Member

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    I stopped reading when it just got rude.
     
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