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Odourless Stop Concentrate (Citric Acid) Going Bad

  1. I had a bottle of odourless citric acid based indicator stop open (the concentrate). It has been open for about 6 weeks. I went to mix up some working solution today and noticed strange gelatinous filaments in the solution. I realised I could not use it like that so I phoned the company and spoke to their technical chap. I was told that microbial growth can occur in citric acid stop unlike in stronger acetic acid based concentrates. I was advised that I could carry on using it if I filtered it through a coffee filter. I said thank you, put the phone down, threw the old stop away and opened a fresh bottle.

    I think I may switch to acetic acid based stop in future. I only used the citric acid type as I was processing in open trays in a poorly (not) ventilated darkroom. Now I have a slot processor and there is no good reason to be using the odourless stop especially as it seems to go bad quite quickly.
  2. get yourself down to the greengrocer and buy 5 litres of white vinegar. (non-brewed condiment it's sometimes labeled)
    should cost about £2.50.
    dilute 1:4

    make sure however it doesn't have flavourings added.
    I bought some once with pimento.

    my pictures got rather spicy for a while
  3. I use citric acid as a stop bath. I buy it in a powder form which I mix a tablespoon per liter of water right before I use it. I toss it after I use it.
  4. Bacteria and Yeast can decompose Citric Acid.
  5. Yes they can use it as food. Actually we can metabolise it too, it's called the Citric Acid Cycle and is absolutely essential for life (Kreb's Cycle). I never really did pay enough attention to undergraduate biochemistry.... I thought the concentrate would be too strongly acid to support microbial life. Evidently not.
  6. Add 1g/l of Benzoic Acid to the stop bath. This retards the growth of "bugs".

  7. PE, Thanks for the tip!
  8. It's a food additive also known as "sour salt". I prefer a citric acid stop over the pungent order of acetic acid which is vinegar.
  9. True the reek of vinegar is not pleasant but now I'm not using open trays it should not be a such an issue.
  10. Incredibly bad advice from the manufacturer. If the microbes are capable of chewing up citric acid just think what they can do to a gelatin based emulsion. Does anyone want to infect their film or prints by attempting to use this stuff.
  11. Try adding 10% of 70% isopropyl alcohol, works for me when added to the final film rinse in 2 drops/500ml photoflo.
  12. Yes, I thought that too which is why I have thrown it out. I think I am going to switch to a highly concentrated acetic acid stop concentrate in future. The indicator feature sounds useful but really is not very useful to me; I never use the working solution to anywhere near exhaustion. I use a slot processor and all of the chemical baths are replenished at the same rate so exhaustion is not going to happen.
  13. +1
  14. I have good experience with Ilford Ilfostop which is citric acid based. I use in the Nova slot processor and keep another batch in a PET bottle for film. I use it up until it starts to change colour which can take a few months. I mix it with plain tap water and never have seen any growth of anything in it.
  15. Perhaps there is a preservative in Ilfostop. This problem was NOT with Ilfostop but I not not going to "name and shame" the manufacturer on the basis of one bottle of concentrate going bad. Having said that, the manufacturer clearly knows it does go bad with reference to my telephone call to them.
  16. I wonder if the Ilfostop concentrate is more concentrated than the product you were using? If so, that might help prevent the "growth" that you are concerned with. The Ilford product is designed to be diluted 1+ 19.
  17. Matt, there are any number of bug inhibitors that can be used. Just as a thought, Kodak E6 or C41 final rinse contains one (as well as Photo Flo) and most aldehydes such as Formalin will do the trick. So it is not impossible to make a bug stable stop with citric acid.

  18. To be fair to whomsoever produced your stop-bath, I have had similar problems with Ilford's citric acid stop in a Nova slot processor but this was only after a considerable non-printing period. Leave citric acid stop in any kind of open container, even a slot container with its tube fitted and I suspect that "bugs" will grow

  19. Ron, do you know of any sources? I checked Artcraft, Photoformulary, and Bostick-Sullivan - none of them list it.
  20. Somewhat surprisingly. the OP's problem is with undiluted concentrate, not working strength solution.
  21. God point, Matt. I cannot recall ever seeing growth in the Ilford concentrate and mine has been open for a lot longer than 6 weeks.

  22. Steve, I'm sorry but IDK. Some of these places have unlisted chemistry that they will sell. You might try ANTEC chemicals or ESP chemicals. They are most helpful.

  23. These beasts are quite specific on their food.
  24. This product is also 1+19. It's a bit annoying as I have several unopened bottles of it. I use an online supplier and so I tend to stock up when I make an order so as not to have repeated delivery charges on small orders. The manufacturer asked for the batch number and it isn't old stock.
  25. Citric acid stop baths are excellent media for some bacteria. You may be seeing the beginnings of a culture. I once had a tray develop a full grown culture over about two days.
  26. A bit off topic but ... Awhile back big brother decided that kids were "huffing" glue to get high. They required that oil of mustard be added to the glue to make its smell irritating. Sort of spoils the experience of building models for everyone else. :sad:

    I realize that kids need protecting but it reminds me a bit of the old definition of puritanism: "The vague, uneasy feeling that somewhere someone is having fun." So the honest model builder or handyman is collateral damage. I don't know if mustard oil is still used but using such cements indoors was quite a challenge. Far better to limit sale of glue to adults.
  27. I wish they'd ban crack. I just can't keep still
  28. I hadn't thought of that- good point. I use sodium metabisulphite as paper stop in a Nova vertical slot processor. It sure isn't odorless (SO2): in a tray it would be nasty but in the Nova in a moderately ventillated darkroom it's ok. I chose it because I thought its carry-over to neutral pH fixer would be more compatible. Now I have another reason: bugs aren't going to grow in it!

    I sympathise with those whose memories are activated by the small of acetic acid. We still have a commercial print processor nearby and the acetic acid aroma never ceases to bring back fond memories. But my own darkroom has its distinctive aroma (mild fixer) and I love that too.
  29. Prompted by this thread I got my 2x 1 litre brown glass bottles of ready to use stop and fixer out of the cupboard. Holding up to the light I can see both have these tiny filaments floating about in them that certainly were not there a month ago, bugger only done a couple of rolls with them. Luckily the part used bottles of concentrate seem fine (Ilford ilfostop and rapid fixer). Tempted to get a cheap beer fridge to stash in the corner of the house somewhere for all this film stuff.