Measuring Graduate Turning A Milky Colour

Discussion in 'Talk About Developing Film' started by Ian-Barber, Mar 10, 2018.

  1. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    I have noticed that the plastic of two of my measuring graduates, mainly the ones which I put the developer in (not Paterson branded) appear to be going a milky colour. Rinsing with water returns the plastic to close to its original colour but after its dried the milky colour returns.

    Is this just a side effect of what could be cheap plastic or could it be something else.
     
  2. David M

    David M Active Member Registered User

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    They are probably polystyrene. I think it's the effect of age and micro-cracking. Water is filling the cracks. I have some that were made by Photax from polypropylene with don't suffer from this, although they do need de-staining from time to time. The best thing about them is that they have click-on bases in different colours so each solution is clearly identified. I don't think they are made any more.
     
  3. Stephen Batey

    Stephen Batey Well-Known Member Registered User

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    The only thing that suggests itself to me are small abrasions that scatter the light like ground glass, but when filled with water the abrasions are filled in and the plastic appears clear again. I don't know if this can be confirmed (or rejected) by visual inspection under a loupe.

    Edit - David's post above was made while I was typing. You wait an hour for a reply, and then two come along together :D
     
  4. Ian-Barber

    Ian-Barber Admin Staff Member Registered User

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    After further inspection I think you are correct Stephen, I have a plastic stirrer which I use and I think over time it has scratched the plastic of the graduate.
     
  5. Alan9940

    Alan9940 Active Member Registered User

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    One word: Paterson. :D

    3 of my graduates are nearly 40 years old and perfectly clear. I now, also, have two 600ml Paterson graduates that I bought recently; we'll see what they look like in another 40. ;)
     
  6. Graham Patterson

    Graham Patterson Member Registered User

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    If it is just scratches on clear polystyrene, you may be able to polish them out. A good dab of (cheaper) toothpaste on the end of a soft tool can help. If the plastic is crazing (think crazy paving texture), then it is probably going to collapse at some point. I have an older Jobo where the 270ml measures are going at the top.

    I have seen some cheap plastic measuring jugs in supermarkets that should be fine for mixing normal chemicals, but not measuring them. If they get scratched up it is not so bad or expensive to replace as a graduated cylinder. I do a lot of mixing in a stainless steel jug. It won't scratch and it is easy to warm it up.
     
  7. David M

    David M Active Member Registered User

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    https://en.wikipedia.org/wiki/Crazing
    The second paragraph under Polymers mentions the whitening of polystyrene. It tells me much more than I want to know.
    The supermarket jugs can easily be checked by adding a weighed quantity of water, preferably using a digital scale.
    [Aha! I've just had the thought that there's no need to mark conventional graduations; you could mark the exact quantities that you use in practice. (16US oz for the Strearman tank for instance) Or you could covert entirely to using weight. I haven't done this myself.]
     
    Last edited: Mar 14, 2018
  8. Stephen Batey

    Stephen Batey Well-Known Member Registered User

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    As a trip down memory lane, when I first started making contact prints (before I'd started developing films) I used Johnson's Pactum universal developer and hypo crystals. I used a saucer as a developing dish, and not having any graduates or measures weighed the water on kitchen scales.

    I suppose if we are being really picky, we could argue that as water expands and contracts with temperature, we should either make all our measures at the same temperature or simply weigh it. In practice, I suspect that scales would give a more accurate result than squinting at the meniscus level and cetrainly better for larger volumes which usually are measured in wider graduates.
     
  9. David M

    David M Active Member Registered User

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    I suppose all the solutions would be in the same room and thus at the same temperature, but in practice I can't see it making much difference. The zero function on digital scales could mean using only one container to make up a solution instead of two. I might have to try it.
     

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