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  1. #11

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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

  2. #12

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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.

  3. #13

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    Quote Originally Posted by Jorge
    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.
    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?

  4. #14
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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

  5. #15

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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/
    Tom Hoskinson
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  6. #16

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    Quote Originally Posted by Tom Hoskinson
    Jim, I recommend dissolving the phenidone and catechcol in propylene glycol (PG) as the "A" stock solution.

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

  7. #17

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    Quote Originally Posted by j_landecker
    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?
    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.

  8. #18

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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.

  9. #19

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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.
    Tom Hoskinson
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  10. #20

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    Quote Originally Posted by Tom Hoskinson
    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.
    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!
    Tom Hoskinson
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