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  1. #1
    dlin's Avatar
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    Color of Pyrocat HD "A" solution in glycol

    I received some propylene glycol yesterday to make a longer-lasting stock solution "A" for Pyrocat HD developer. All of my chemicals were purchased from Artcraft Chemicals, and I've had no problems with them in the past using water to create the stock solutions. The water-based stock "A" solution ends up being a light tan color. This time, putting up the catechol in heated propylene glycol produced a vivid and deep reddish-orange colored solution. Have any other users noticed a difference in color between glycol- and water-based stock "A" solutions? I have not developed any film yet with the glycol- based stock, as I'd like to know ahead of time whether this color difference is indicative of a problem. Thanks for your help.

    All the best,
    Daniel

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    Quote Originally Posted by dlin
    I received some propylene glycol yesterday to make a longer-lasting stock solution "A" for Pyrocat HD developer. All of my chemicals were purchased from Artcraft Chemicals, and I've had no problems with them in the past using water to create the stock solutions. The water-based stock "A" solution ends up being a light tan color. This time, putting up the catechol in heated propylene glycol produced a vivid and deep reddish-orange colored solution. Have any other users noticed a difference in color between glycol- and water-based stock "A" solutions? I have not developed any film yet with the glycol- based stock, as I'd like to know ahead of time whether this color difference is indicative of a problem. Thanks for your help.

    All the best,
    Daniel
    I don't know the anwer to your question. But I have not had a problem of color. What I do is mix the sodium metabisulfite and potassium bromide first in the glycol at 260º F or so and allow them to completely dissolve, and then I let the temperature of the solution go down to about 160º F before adding the phenidone and pyrocatechin. I mixed a batch up just yesterday this way and it is completely clear. The key to clear solutions, in my experience, is keep the solution at 160º or less when adding the pyrocatechin and phenidone.

    The only way to know for sure whether the color means anything in your case is to develop a sheet of film and see what happens. There is the possbility that the coloring is from some kind of food dye but I would also be concerned that the heat has negatively impacted the reducers. Once when mixing some PC-TEA I added the the phenidone with the glycol at about 250º F and the resulting solution was heavily colored and the working solution was weaker than it should have been.

    Sandy

  3. #3
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    When I first made up a glycol A solution to simulate Pyrocat for my article in PT I left out everything but the catechol and phenidone, figuring anything else could be put into the B solution. That solution is a light tan color. Catechol's first cousin, hydroquinone, makes a pretty clear solution in glycol. Both of these as well as pyrogallol are more easily dissolved in glycol than ascorbic acid. Sandy is right that the temperature need not be at 250 F to dissolve the developing agents in Pyrocat HD.
    Gadget Gainer

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    dlin's Avatar
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    Thank you for your suggestions. I have remade the solution at a lower temperature (140 F), and the color is a bit lighter. The catechol dry chemical I received clearly has a color (crusty brown flakes), so that might be contributing to what I'm seeing. I will give this solution a try.

    Daniel

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    Quote Originally Posted by gainer
    When I first made up a glycol A solution to simulate Pyrocat for my article in PT I left out everything but the catechol and phenidone, figuring anything else could be put into the B solution.
    I would guess that there would be not the slightest problem putting the potassium bromide in solution_B.

    But would there be any problem in putting the metabisulfite into the potassium carbonate solution? Would there be a reaction between them? Would it last as long?

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    Quote Originally Posted by dlin
    Thank you for your suggestions. I have remade the solution at a lower temperature (140 F), and the color is a bit lighter. The catechol dry chemical I received clearly has a color (crusty brown flakes), so that might be contributing to what I'm seeing. I will give this solution a try.

    Daniel

    My current stock of Pyrocatechin came from Artcraft and is slightly off-white in color. I experimented with an older stock that Clay Harmon sent me, and it was different from my current stock, more like the crusty brown flakes you describe. But it worked fine, and in fact I mixed a small amount of it in glycol and the color was quite clear.

    Sandy

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    My Pyrocatechin came from Artcraft, my Phenidone came from Ilford (many years ago) and my propylene glycol came from The Chemistry Store. My Pyrocat-HD "A" solution is clear and it works fine (it is the last of a liter I mixed up about a year ago).
    Tom Hoskinson
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    Having just sent to Formulary for my first batch of Pyrocat, I'm curious about the shelf life. I ordered the liquid kit (for 50 L) which has not arrived yet. What time limit am I looking at for the "A" solution?

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    Quote Originally Posted by noseoil
    Having just sent to Formulary for my first batch of Pyrocat, I'm curious about the shelf life. I ordered the liquid kit (for 50 L) which has not arrived yet. What time limit am I looking at for the "A" solution?
    From my own work and reports of others the shelf life of Stock Solution A, mixed in water, is about one year. Whether or not it makes sense to mix in glycol depends on how much film you plan to develop within that period of time. My own feeling is that if you mix the Stock Solutions in 1 liter or more sizes it would work out better for most folks to mix in glycol. The shelf life in glycol is in theory like HC-110 concentrate, i.e. it should last for years and years without going bad.

    Sandy

  10. #10
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    I think the metabisulfite is for preservation of the water A solution. When you mix the A and B, it turns to sulfite and has a slight effect on the pH. If you use glycol as a solvent, you do not need preservatives in the A solution. Anything you do need that is not subject to decomposition or that is easilly mixed at time of use, I would leave out of the glycol.
    Gadget Gainer

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