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  1. #21
    AllanD's Avatar
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    I don't like the idea of selenium on the garden. If in years to come someone grows cabbages or one of the many other types of brassica on this plot, then these will draw the selenium out of the soil and concentrate it in a food crop. Brassicas are used in this way to clean up old industrial sites. In certain places (Stroud in the UK for instance, although it is cadmium in this case), residents are advised not to grow these crops for fear of concentrating naturally occurring poisonous metals in their food crop. The problem is that this kind of contamination can remain in the soil for years.
    Heat or light; it depends on your sensitivity.

  2. #22

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    Quote Originally Posted by AllanD
    I don't like the idea of selenium on the garden. If in years to come someone grows cabbages or one of the many other types of brassica on this plot, then these will draw the selenium out of the soil and concentrate it in a food crop. Brassicas are used in this way to clean up old industrial sites. In certain places (Stroud in the UK for instance, although it is cadmium in this case), residents are advised not to grow these crops for fear of concentrating naturally occurring poisonous metals in their food crop. The problem is that this kind of contamination can remain in the soil for years.
    Yes fair point in theory, but it is a matter of concentrations and total quantity. The concentrations of toxic substances in the soil in industrial sites as well as the quantity over the whole site as a whole can be absolutely enormous! I dont think a private user dumping a few lites of working solution every 3 months into the hundreds of tonnes of soil in his back garden can be compared. Wouldn't the selenium would distribute istself far and wide and thus become even more dilute than it already is? We need an industrial land reclamation expert!

  3. #23
    ann
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    that is a good question. The prints are washed after the selenium has stopped working and thrown away.
    The selenium converts the silver to silver selenide, so it isn't the same as just tossing out active selenium.

    I think the whole question comes down to how much selenium is being discarded, not that it is discarded.

    As with most other things in life, one makes a decision based on their own experiences, and their beliefs . Which means there just isn't one way to do things.

    Holly asked a good question about something she knew nothing about, she nows has a variety of answers which should help her decide what she needs to do.

    As tom suggest "if some people take a very cautious approach that cannot be a bad thing" . That is the road we take at our lab. Is it for everyone? That is up to the users.

  4. #24
    Bob Carnie's Avatar
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    I agree with being careful with spent chemistrys and pass these onto the reclamation experts.
    Volumes of chemistry seems to be a problem here. I have a lab enviornment, therefore I would assume I use more chemistry than most. But in the GTA (toronto) there are numerous private darkrooms in homes , surrounding me. If lets say 4 of these darkrooms are active on a weekend and start producing shows or portfolios for themselves , they then would be producing more spent chemistry than my lab. Is it ok to dump since each darkroom is a hobby enthusiast ??
    Any one working with our craft chemicals should be fully aware of any potential harm that these chemicals can cause inside and outside of their darkrooms. Sadly there are so many different arguments for or against dumping.
    I will say this , my Honey is a gardener and printer, if she starts dumping the spent selenium on our radishes I think Im out of here.

  5. #25

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    how you know when selenium toner is exhausted?

    Quote Originally Posted by Mongo
    Two points:

    First, I never mix fresh selenium toner. As my toner gets exhausted I just keep adding concentrate as necessary.
    How?
    Jose A. Martinez

  6. #26
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    Quote Originally Posted by Jose A Martinez
    How?
    I find that if I wait until my toner is taking about 50% longer than when it was fresh and I add 7.5% of concentrate by volume, I get back very close to my original toning times. (I originally mixed at 1:9...I get close enough to that using this method.) I add a bit of water to bring the whole thing back to 2L (but it never takes much water to do that).

    I've never tested the solution to find out what the actual concentration of selenium is (and I have no idea how I'd go about doing that), but this method has worked for me for quite a whlie.

    It is important to filter the solution occasionally...again, I don't know why, but I do know that it is. I use unbleached coffee filters and a funnel that I reserve for use with selenium toner only.
    Film is cheap. Opportunities are priceless.

  7. #27
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    When you start to see a lot of little black bits (silver selenide), your Se solution is starting to go. When you accumulate a lot of this precipitate, you should notice that it is taking longer for you prints to tone. This is the time to throw it out. In many soils, particulary in the arid SW US, Se is encountered relatively in high levels. When these levels get too high, it will effect plants. I think dispersing it in the soil is the best way. Typically, I find that a 1/2-gallon of working 1:20 solution will do about 40 or more 8x10 prints before it gets to this stage.

  8. #28

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    Thanks, Mongo and Hortense.
    Jose A. Martinez

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