My Bleach has gone Blue?

Discussion in 'B&W: Film, Paper, Chemistry' started by hywel, Jan 5, 2008.

  1. hywel

    hywel Member

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    The last two batches of bleach for Kodak Sepia I made up, having sat unused in it's bottle for a couple of weeks, has changed from it's original yellow colour to a blue. Moreover it has stained the (translucent plastic) bottle blue as well. I threw the first one away and made the second, kept it in a new bottle, but it's done the same. Both worked fine the first (and only time) I used them.

    My previous batch of bleach lasted me about six months, possibly longer, never anything but yellow in colour.

    I cannot think of anything I've changed but something obviously has. Anyone have any ideas?

    Hywel
     
  2. Ole

    Ole Moderator Staff Member Moderator

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    I assume that's a ferricyanide bleach. :smile:

    what has happened is that some of the iron in the ferricyanide has become reduced to ferro. This then reacts with the remaining ferri- forming an insoluble blue deposit. That's the same blue stuff that makes up a cyanotype.

    So either your mixing water or your bottle is contaminated with either something reducing (like most organic matter) or a ferro compound.
     
  3. hywel

    hywel Member

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    Ole, thank you, a very clear answer. And yes, Potassium ferricyanide.

    If it is the mixing water that is the cause and it's the same water I use for the whole of my photographic process, all mixing and all washing, are there going to be other problems? Something nasty that will show up in a few years time?

    It can't be the bottle, I've used two and the first one had yellow bleach in it for the previous year.

    But I may well have made those original old batches up with distilled water, I used to use it quite a lot. Now I don't bother. I do not trust my local water (when it sometimes comes out of the tap brown I just think perhaps all is not well) but I now have two filters in the line and use this water for everything.

    Need to go and mix a new batch with distilled water. Will know in a couple of weeks if it was the problem.

    Hywel
     
  4. Ole

    Ole Moderator Staff Member Moderator

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    Most photographic chemicals are well buffered and full of sequestrants - which in English means that they should be able to handle any "nasties" in the water. So if your tap water is filtered I believe that should be fine.

    The brown colour of the (unfiltered) water is either organic "stuff" or iron compounds (could be both), which are exactly what would give blue precipitate in the bleach - especially if the bottle is stored in the light. The good thing is that the blue stuff is totally harmless and practically insoluble, so you can use the bleach even if the bottle has turned blue. if it's really bad you can try filtering it; if what comes through a filter is yellow (or even pale green), it should still work as a bleach.
     
  5. hywel

    hywel Member

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    I thought about trying out the blue stuff, even thought of filtering it. Then decided that the print I was working on was the important thing and threw the blue stuff away and mixed some new with distilled water. Gives me the chance to see if that solves the problem.

    Happy that even if it is the water it shouldn't cause me any other problems. It never has that I've noticed. I just hope that it doesn't show up in the future. Especially as today's two prints are just lovely.

    Thanks again for your help, shall be back in a few weeks if the latest batch turns blue!

    Hywel