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Thread: Pyro-Uno

  1. #31
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    Did you heat the TEA before mixing to drive off as much water as possible? The temperature must be above the B.P. of water, and you should stir it gently with a long handled spoon. You will see steam if it has water in it. That is not TEA vapor.
    Gadget Gainer

  2. #32

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    Quote Originally Posted by gainer View Post
    Did you heat the TEA before mixing to drive off as much water as possible? The temperature must be above the B.P. of water, and you should stir it gently with a long handled spoon. You will see steam if it has water in it. That is not TEA vapor.
    No, I did not. Could there be so much water in TEA that it makes the difference?

  3. #33

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    There may be a problem in mixing TEA with Glycol. Pyrocat-HD mixed in glycol remains clear for years. Pyrocat-MC, mixed in glycol with a small amount of TEA, darkens appreciably after one year, and more after two years. Other than the metol/phenidone difference in the two formulas, the only other difference is the small amount of TEA in Pyrocat-MC.

    The fact that you mixed the 510 Pyro 1:1 with glycol may have accelerated the reaction between the TEA and glycol.

    On the other hand, I have on hand a 510 Pyro solution that is several years old. It was clear for at least two years, but now has darkened considerably. It may or may not still be good, have not tested it with film recently. But as I noted earlier re: the darkened Pyrocat-MC, the fact that it is so dark makes me very suspicious that the reason is oxidation.

    Sandy King



    Quote Originally Posted by Olli J View Post
    Speaking about oxidation, I made recently an unexpected finding which bothers me. About three months ago I mixed 510-pyro developer, it's in TEA as you know. To reduce viscosity I mixed the ready developer with propylene glycol 1+1. Originally the solution had a pale color. After mixing the solution was divided in two parts. Within the first week I developed some films with it and they came out fine. Since then the developer has been undisturbed on the shelve in my darkroom, in well capped glass bottle, about 100ml solution in a 250 ml bottle. A couple of weeks later I noticed that the solution had begun to darken, starting from the surface and proceeding deeper. Now it's all dark but still the solution is darker on the surface than in the bottom. To me it looks like airborne oxidation, but it started much earlier than I would have expected. The other part of the developer was used by another person, who recently reported that his developer also had dark color but still functions as well as earlier, but the "life expectancy" of this developer is not very good.

    I have to admit that my pyrogallol is several years old, but it still looks good, almost white, a little sticky powder. All other chemicals are fresh. Any ideas why the solution oxidized so fast? Could there be a problem in mixing TEA and glycol?

    Olli

  4. #34

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    Gadget Gainer

    Quote Originally Posted by sanking View Post
    Ed,

    First, about the precautions. I wear a mask and make sure that any powder that might get in to the air will go downwind from me.

    Second, the amount of useful practical information Gadget has shared with our community about formulating developers for films and papers is nothing short of amazing. And in large measure, the information he has shared has been empirical data, which I find to be the most useful.

    I had hoped to get out today and do some exposures for comparison testing of Pyro-Uno with D76 1:1. Unfortunately, the transmission on my old Nissan Pathfinder is causing problem and won't allow me to back up. For that reason the Pathfinder is now in the hands of a local mechanic, who to this point (three days and running) has not been able to identify the source of the problem. So here I am, stranded at home and at the mercy of my wife who has a fully operational vehicle.

    Sandy
    I fully agree. Gadget adds so much to our discussions and general knowldege. The information that he supplies is not available easily-if at all-from any other source. Very grateful that he takes the time to help.

    Ed

  5. #35

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    I've been using MC-TEA for something like 3 years. It darkens over time, but it does so evenly, throughout the solution. If the darkening was due to aerial oxidation, I'd expect it to be strongest at the surface, given that TEA is so viscous. That's what happened with a solution I made of phenidone in propylene glycol - it went red at the surface, but stayed clear below that.

    I also haven't noticed any real change in the activity of MC-TEA over time, despite the darkening, though I haven't tested this very carefully.

    Put supposing activity over time is nearly intact, that plus the even nature of the darkening leads me to wonder if it is due to some slow reaction in the solution other than aerial oxidation. Perhaps it's a reaction between impurities.

  6. #36
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    Quote Originally Posted by Olli J View Post
    No, I did not. Could there be so much water in TEA that it makes the difference?
    I believe so. See the hygroscopicity chart I posted earlier. In 50% relative humidity the equilibrium weight gain is 20%. A liter of dry TEA weighs 1126 grams. In equilibrium with 50% humid air it will weigh 225 grams more. I don't really know how much water it takes to allow developers dissolved in TEA to become active. I once placed a piece of film in a saucer of PC-TEA in light and saw no response over some period of time, but do not remember how long. It was reported in my original article in Photo Techniques. You can do the same sort of experiment with HC-110 concentrate with the same results. But add a bit of water and see what happens.
    Gadget Gainer

  7. #37

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    Any updates ?

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