Hello from East Yorkshire

Discussion in 'Say Hello & Introduce Yourself' started by Damnfinecoffee, Feb 14, 2018.

  1. David M

    David M Active Member Registered User

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    I have the old holders with solid backs and I haven't seen any similar effect. I suppose if it was there, it would be evenly spread all over and so, for practical purposes, invisible. I did get some slightly, very slightly under-fixed patches until I drilled a hole in the centre to help the flow. I can see where the ribs were on a wet negative, but this vanishes when they are dry.
    All I can think of is that you are getting slightly less efficient removal of the backing where contact occurs. Maybe your agitation is a little too gentle to penetrate this narrow gap. I swing the tank upside down so that the liquid falls down through the film assembly and then swing it back again to repeat the effect.
    Do you use a pre-soak? I don't see how this would make a difference, but it's another factor. I always pre-soak. Does Ian?
    Is your tank at the same temperature as the developer? Could a cold or warm holder be altering development slightly where it touches? A pretty desperate idea, I know.
    I'm afraid I've run out of ideas, however improbable. I do hope you find a cure.
     
  2. martin henson

    martin henson Admin Staff Member Registered User

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    Yes always presoak, so does Ian. I use a tempering unit so everything is stable temp, might try a more vigorous approach and do a side inversion as well as a frontal.
     
  3. David M

    David M Active Member Registered User

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    I suppose as a last ditch remedy, you could make a holder-shaped selection mask in Photoshop and apply a gentle correction through it. Better you than me.
     
  4. David M

    David M Active Member Registered User

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    A more sensible approach, rather than my wild Photoshop scheme would be to take a shadowed negative and re-fix it in an open tray. To be doubly sure of the exact cause, a second neg could be simply re-washed. It does seem reasonable to suppose that that the negative is being masked by the holder. I think the SP-445 tank is the only one where anything other than the chemicals are touching the surface of the neg.
     
  5. Ian Grant

    Ian Grant Active Member Registered User

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    A pre-soak can itself lead to uneven development which is why no B&W film manufacturer recommends one. Many film (and paper) emulsions contain surfactants, these help in the coating process but are also there to help with more even development. However their level is low and a pre-wash can remove them and that can lead to problems of uneven development as you fill a tank.

    It's a bit of a grey area because you really need to use a pre-soak with rotary processing. A lot will also depend on the developer used as well, because many commercial developers also contain a trace of surfactant.

    When I move to Turkey in 2006 I began having unexpected processing issues, in my case air bells, I was using Pyrocat HD that I make from raw chemistry (it would be the same if bought pre-prepared). I did various tests and eventually began adding a very small amount of wetting agent to the stock Developer (Part A) talking drops no more or you'd get foaming which is just as bad if not worse. In this case it was the high mineral content of the tap water used for dilution.

    I don't use a pre-soak, the few time I tried with a Jobo 2000 tank I got uneven processing, you have to find what works best with your own equipment, film, and developer.

    Ian
     
  6. David M

    David M Active Member Registered User

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    Interesting.
    I began using a pre-soak for tray processing, because of the fear of getting two sheets stuck together in an active solution. Subsequently, I've moved to a tank but continue to pre-soak. I've never observed any adverse effects.
    I inadvertently avoid air bells too. My darkroom has no running water (One day, I keep telling myself.) and I keep a camping jerrycan of filtered water for mixing. I refill it after each session so the water stands and de-gasses itself until the next time. Washing is in the bathroom, which would be a nuisance if I were more productive.
    I've never used rotary processing for film. I'd like to know why pre-soaking is different in this case.
     
    Last edited: Feb 20, 2018
  7. martin henson

    martin henson Admin Staff Member Registered User

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    I think you are more likely to get uneven development without a presoak with stand or EMA method (semi stand). The other thing to remember if you presoak at the development temperature you will not get a temp drop leading to more even dispersion of the chemicals.

    For short to normal dev times I don’t think a presoak is as critical and would say not nessesary, maybe this is what the film manufacturers mean, although through habit I still do it with no adverse effects.
     
  8. David M

    David M Active Member Registered User

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    Yes. I wonder if this advice relates originally to deep tanks, where the film comes in contact with the developer very quickly and irregular carry-over from a pre-soak would dilute the developer tank unpredictably. A long time ago, I developed X-ray film in deep tanks without a pre-soak and with no apparent problems. The business of X-raying steel castings is much less refined than producing fine prints.
    We do seem to be coming to a consensus that pre-soaking is a matter of personal preference. Its usefulness might depend on the hardness of the local water, perhaps.
    I'm still wondering about flow mechanics in rotary machines. I can understand the desirability of stabilising temperature, but that would be common to all processes.
     
  9. Ian Grant

    Ian Grant Active Member Registered User

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    In my 50+ years of film processing the first I came across any bath before the developer was with colour processing where a preliminary-hardening bath was used with reversal processing, it wasn't needed for negative films.

    Later a pre wash tempering bath was recommended for home processing when colour processing switched to C41 and later E6 which are both used at 38ºC rather than 20ºC of E3 and C22, E4 used 28ºC but was never available for home processing as the chemistry was too toxic. This tempering bath was to warm the tank and film and prevent a drop in temperature when the developer was added, it wasn't used in commercial processing.

    It's about volume, commercial processor or deep tanks aren't affected in terms of a temperature shift when flims or reels/hangers are added. But when rotary processing became more common, initially for colour printing, you had big tanks and much lower volumes of developer initially because the processing was at 20ºC you either rotated the tanm by hand or a small mootor roller, but with RA4 and again the 38ºC processing you see a change to the Jobo's etc with their heated tempering tanks.

    When I bought my first Jobo 2000 tank around 1976/7 there were no rotary film developng tanks (they are inversion tanks).

    It was Jobo and other rotary tank manufacturers who introduced th eidea of the pre-soak, and also chemistry manufacturers for E6/C41.

    Ian
     
  10. David M

    David M Active Member Registered User

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    So, presumably the tanks that use a water bath don't really need a pre-soak for temperature control, because they can use a period of initial rotation without chemicals to warm the tank. I had imagined that the soak was to encourage a rapid spread of the small amount of developer along the axis, to avoid streaking.
    The Paterson Orbital has been mentioned elsewhere on the forum. This used a warming pre-soak. It operated at room temperature, and processing began above the official process temperature, then drifted downward, so that the average gave correct results. Paterson provided a rather flimsy calculator to give the correct pre-wash temperature for different ambient and processing temperatures.
     
  11. Ian Grant

    Ian Grant Active Member Registered User

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    It's about volume, My Jobo 2000 tanks are the same size as the later Rotary Jobo tanks but fills from the bottom as you pour the developer in the top via the central column, this can be done quite quickly and is followed by a few inversions. But a rotary tank isn't filled to cover a reel (or two) and leaves part of the film out of the developer which could lead to streaking etc and you run the risk of splashing developer on areas of film not submerged, the pre-soak slows down the initial development and helps prevent streaking. So just warming the rotary tank is not a good option.

    A lot depends on where you're processing as well. When I'm in Turkey I process at 27ºC and can keep to within +/-0.2ºC with no effort as that's the "cold" water temperature most of the year, but in the UK at my old house I had no central heating and had to warm my tank in the winter and used two 5 litre jug as a tempering bath for the developer etc and the tank.

    I have used a Paterson Orbital but at a friends in Turkey and there was no need to use a pre soak due to the ambient temperature plus they fill really quickly. I have a similar flimsy Paterson calculator that cam e with a colour print drum.

    ian
     
  12. David M

    David M Active Member Registered User

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    Yes, it's the risk of splashing that makes me use a pre-soak. I also imagine having to pause in pouring – a sneeze, a slippery grip on the graduate, an undetected kitten under the feet, a sinister knock on the darkroom door... I visualise the level stopping and leaving an ineradicable sharp line halfway up the neg. As both you and Ilford say, pre-weting the emulsion slows down penetration of active chemicals and my hope is that any boundary would be blurred. As this happens either inside my head or inside a sealed tank, it may all be superstition.
    The Orbital was a well-thought-out piece of kit, I thought.
    (A note to prospective users of the Orbital for film development: There are a couple of things you may need to modify to make it more suitable for film. They are well-documented on the web.)
     
    Last edited: Feb 23, 2018

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