What happened to my Pyrocat?

Discussion in 'B&W: Film, Paper, Chemistry' started by j_landecker, Jun 28, 2004.

  1. j_landecker

    j_landecker Member

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    Hi everyone...heh, my first post here after much lurking...

    Until yesterday I've been very happy with the negatives from my home-mixed Pyrocat, and was thinking it could become my main developer. My original 100 ml batch, now 2 months old, is about 2/3 gone, and I've been processing some film every weekend for the last few weeks with some really great results. Yesterday, however, my Pyrocat experience suddenly took a turn for the worse.... I shot some 4x5 Classic 200, exposing it at ISO 100 and processing it in my Jobo (1:1:100) as I've been doing, and every one of my negatives looks severly underexposed! The shadow areas are beautifully clear, and there's hardly even any midtone density, but the highlight areas are quite dense....it's as if the film took a sudden dive in effective speed. After racking my brains trying to figure out whether the problem is equipment or exposure related, I came to the conclusion that it must be the developer. So today I shot some test negatives of a contrasty sunlit scene, all at the same exposure, and developed one in Pyrocat and the other in Xtol. The Pyrocat negative has the same look of severe underexposure, while Xtol produced a full negative, consistent with the metering technique I've been using all along.

    So what happened to my Pyrocat? One possibility that occurred to me is that the phenidone in the part A has conked out. If I've got the concept right, phenidone is usually superadditive with a second developing agent in a developer, in this case catechol. My negatives still show a brown stain, implying that the catechol is still doing some work, but without the kick of the phenidone, it's only active enough to develop the highlights. Since I mixed the stock solutions using spoon measurements, I'm wondering if I had too little phenidone...enough for the developer to work for a while, but too little to resist decay in the slowly emtying glass bottle. Come to think of it, the diluted solution doesn't have the pinkish or tan color it may have had originally....but I'm not sure.

    Do these conclusions make sense to anyone, or has anyone had a similar experience? I keep the solutions in 100ml brown glass bottles, but are there better storage ideas?

    Thanks for any ideas....

    Jim
     
  2. john_s

    john_s Subscriber

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    I had exactly the same result from my first batch of Pyrocat-HD, but right from the start. At the time, I put it down to bad phenidone, since the other chemicals have proved since then to be ok. I don't believe that I made a mistake in mixing.

    I need to make the following admission to not following the instructions completely. I made up a stock solution of 5gram phenidone in 100mL of alcohol (95% food grade). I used the appropriate amount of that stock solution

    My next batch was using metol (at Sandy's recommended amount) instead of phenidone since I was worried about my source of phenidone. I have been absolutely delighted with the metol version, and I get at least EI 320 out of Neopan 400, which is fast enough. Probably a bit more with minimal agitation.
     
  3. sanking

    sanking Member

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    If the developer was working fine when you first mixed it I believe you should discard the theory that there was too little phenidone. The amount you need anyway is miniscule and in my experience it would not go bad in two months in a partially full bottle.

    The two most likely reasons why the developer may have failed, in mind would be.

    1. Somehow either one or both of the stock solutions was contaminated.

    or

    2. You failed to add the B solution when mixing the working solution, or the B solution is mislabeled and contains something other than potassium carbonate at the necessary strength.

    The very thin negatives that you describe would in fact be what one would expect from using a very weak Stock B solution. This is the accelerator part of the developer that increases the working solution to the pH needed for development, and without it the catechol and phenidone will just sit there and do nothing.

    Next time you mix a working solution check the pH if you the means to do so. It should be around pH 10.9 or so.
     
  4. j_landecker

    j_landecker Member

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    Sandy,

    Thanks for the information and for debunking my chemistry "theories". The solutions were definitely from the right bottles, so I guess that leaves contamination. I use a pipette with a rubber bulb on the end to measure out the concentrates, and although I try to wash it out thouroughly, a few drops of tap water are always left inside. The rubber bulb is also hard to control, and if I suck up too much concentrate, I squirt the excess back into the bottle, but maybe I shouldn't do that! I'll try to mix up some new sol'n B, and see what happens...

    Jim
     
  5. PJC

    PJC Member

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    Greetings Jim,

    It's been my experience that you need to be extremely careful when using pipettes, because contsmination is very easy. Your best recourse is to use pipettes dedicated to each solution, or small graduated cylinders, again dedicated to each solution. I try never to put excess stock solution back into the bulk container and never had a problem with contamination of this type.

    Regards, Pete
     
  6. Jim Chinn

    Jim Chinn Member

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    I have discovered that the best way to avoid contamination is to get a graduated cylinder small enough to accurately measure small amounts of chemistry. I have a couple that measure 10ml in (1cc?) increments.

    if you want to use pipettes, the best procedure is to have several on hand and never use the same one twice when measuring chemicals. This way you are sure you have a clean one for each different solution. Wash them up when you are done and you are ready to go next time.
     
  7. roy

    roy Member

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  8. john_s

    john_s Subscriber

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    I use 10mL pipettes with some rubber bulbs that have a valve at the top (for expelling some air) and below (for controlling the amount of liquid sucked up). They are from a lab supplier. The valves are simply moulded into the bulb, and release very gradually with pressure from finger and thumb, so the movement of liquid up the tube is slow and steady if you want it to be.

    Smaller ones are available, and would be adequate for me in terms of volume, but they're harder to rinse because of their narrowness.
     
  9. philldresser

    philldresser Subscriber

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    Dear all

    I have been using the same pyrocat premix solutions for 8 months with no let-up in effeciency. For dispensing of the 2 solutions I use childrens medication syringes which are calibrated to 5ml (in 1ml increments) and cost under a £1 each. You can take them apart for cleaning (and drying) plus they come with a rubber stopper for the top of the (100 ml medicine) bottles that use. I have labelled each one so reduce risk of contamination. This works very well for me.

    Phill
     
  10. Leon

    Leon Member

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    i use those little medication syringes too, have done with all of the 2 solution developers I have used with no cross contamination at all - and the pharmacist gives me them for free!
     
  11. j_landecker

    j_landecker Member

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    Hi again, back with an update.....

    It turned out that my part A was bad. When I poured the rest of the bad part A into a clear graduate, it was colourless or perhaps slightly yellowish, rather than the pinkish colour of the freshly mixed stuff. I also noticed right away on my first test run with the new solution that, after developing, the developer came out clear and with the same dye colour as the prewet, whereas the bad batch was coming out dirty brown and clearly oxidised. I don't remember what the previous batch was like when new.

    Mixing up the new batch brought up some other questions about getting the proper 0.2 g of Phenidone for 100ml of concentrate. How are others handling this? In The Darkroom Cookbook, Steve Anchell suggests making up a solution of 2g Phenidone and 6g Sodium Bisufite in a litre of water. This would require using 100ml to get the 0.2g of Phenidone, which is not very practical for the mixing order in the formula. What if I started with 70ml of this Phenidone solution, add the other ingredients, and then top up to 100ml from the Phenidone solution? Another idea would be to make the Phenidone solution with 10g of Sodium Metabisulfite substituted for the Sodium Bisulphite, so the 100ml would have the right amount both of those ingredients in it. Would this different mixing order cause any problems? Any idea what the life of such a solution would be? It would take me a while to work through a litre, although 500ml would also be a mixable amount. I tried mixing 5g of Sodium Metabisulfite and 1g of Phenidone in 100 ml of water (with the idea of using 20mls in my 100ml concentrate), but the Phenidone was hard to dissolve, and after cooling down it came out of solution again.

    Also on the the subject of the Potassium Bromide, how well does a 2% solution of this in water keep? It might be convenient to have a few small bottles of these solutions to mix up, leaving only the Catechol to dissolve from solid.

    Thanks,

    Jim
     
  12. Jorge

    Jorge Inactive

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    I have always just poured 5 or 10 ml of alcohol on the phenidone, dissolve it and pour the solution in the water with the rest of the ingredients. So far I hav not had any problems doing it like this.
     
  13. j_landecker

    j_landecker Member

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    Jorge, are you using a scale to measure the Phenidone? 0.2 g is such a small amount, and I'm using measuring spoons...or do you mix up larger amounts?
     
  14. juan

    juan Subscriber

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    I've always mixed a liter of part A - meaning 2g of phenidone. It takes me 4-5 months to use a liter of A, and I've never had a problem with it going bad.
    juan
     
  15. Tom Hoskinson

    Tom Hoskinson Member

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    Jim, I recommend dissolving the phenidone and catechcol in propylene glycol (PG) as the "A" stock solution. Both chemicals will dissolve in PG around 160F to 170F. The resulting stock solution will last a for very long time. I mix 1 liter of the A solution at a time: 2 grams of phenidone, 50 grams of catechcol mixed in 800 ml of hot PG, then add PG for a total volume of l liter.

    If you wish, you can prepare separate stock solutions of phenidone and catechol in PG.

    I eliminate the metabisulfite, it is not needed with the PG as the preservative.

    I mix a separate 2% stock solution of potassium bromide (KBr) in water: Dissolve 2 grams of KBr in 90ml of water at 125F, then add water for a total volume of 100ml. 10ml of this solution contains .2 gram KBr. Thus, you can add 10ml of the 2% KBr solution to 1 liter of the working developer.

    The B solution and the mixing ratios remain unchanged (mix the B solution in water, not PG).

    I recommend The Chemistry Store for propylene glycol: http://www.chemistrystore.com/
     
  16. sanking

    sanking Member

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    My recommendation would be to keep the meteabisulfite when mixing the stock solution with propylene glycol. It is true that it is not needed as a preservative when mixing with PG, but metabisulfite has another function in the Pyrocat-HD formula, and that is to keep the genral stain as low as possible. When mixed with water metabisulfite produces sulfite and a small amount of sulfite is really important in the Pyrocat-HD formula to keep general stain down as low as possible.

    Sandy King
     
  17. Jorge

    Jorge Inactive

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    I use a scale originally intended for reloading. It measures in grains and grams. I have both a digital one and a "scale" or analog one. If you go to a gun shop they sell them far cheaper than the lab supplies stores and are just as good. Measuring spoons and the like are somewhat unreliable, if you are going to do this I would recommend you invest on a scale. The digital I bought is an RCBS, cost me $90 new and it works great.
     
  18. j_landecker

    j_landecker Member

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    Tom, thanks, that's interesting. Why do you add the KBr separately? Does it not dissolve well in the PG? Also, for 1 liter of part A you'd need the full 2g of KBr...not the 0.2g as you stated.
     
  19. Tom Hoskinson

    Tom Hoskinson Member

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    Sorry, I confused you. You need .2 grams KBr per liter of the working developer. The directions I gave you were for mixing a 2% stock solution (2 grams/100ml water). KBr will dissolve in PG, but requires a higher temperature - around 200F in my experience.

    I prefer to add the KBr to the working developer solution.

    With regard to the metabisulfite, I have mixed Pyrocat both ways, and with the films I am using have seen no differences in developer activity or stain levels (blue channel densitometry). I agree that it is more conservative to leave it in the formula.
     
  20. Tom Hoskinson

    Tom Hoskinson Member

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    Once again, my typing fingers were out of sync with my brain. One ml of Pyrocat stock A should contain .002 gram KBr, so 1 liter of stock should contain 2 grams.

    One liter of working developer containing 10ml of stock A needs .02 grams of KBr, thus 1ml of a 2% stock solution of KBr.

    Sorry!