Paterson Orbital blades

Discussion in 'Darkroom Equipment' started by wintoid, May 5, 2008.

  1. wintoid

    wintoid Member

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    I'm using a Paterson Orbital to develop my 8x10 prints (manual agitation). I basically like the thing but have one niggly problem that I could use some advice about.

    The top lid of the Orbital has 2 "blades" which are obviously intended to help keep the paper bowed in a concave manner to aid circulation of the chemicals. In about 60% of my prints, I am finding I get 2 white lines where these blades have presumably been in contact with the paper.

    So far, I've tried using varying amounts of solution, from the recommended 55ml up to 150ml. I've tried agitating extremely slowly, and also faster. I've spent a fair amount of time trying to seat the prints onto the base of the Orbital because the paper does seem to bow in a convex manner (Ilford MG IV Multigrade RC Glossy).

    If anyone can help me to get rid of these 2 lines, I would be very grateful!!
     
  2. Dave Miller

    Dave Miller Member

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    I have suffered this problem in the past and believe it to be due to incomplete washing of the lid between use. I think traces of fixer remained on the blades which locally kill the developer on the next use.
     
  3. RH Designs

    RH Designs Advertiser Advertiser

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    I used to get a similar problem in the past with Cibachrome. Eventually I worked out that the presoak that is recommended for RA4 processing at higher temperatures also served another vital function - to "stick" the print to the bottom of the processor as it was poured out. Try presoaking the print for a minute or so before pouring in the developer and see if that helps.
     
  4. wintoid

    wintoid Member

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    Both good and probably worthwhile suggestions. Thanks! I'll try paying particular attention to the blades when cleaning the lid, and will also try a presoak.
     
  5. RH Designs

    RH Designs Advertiser Advertiser

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    If the print doesn't stick to the bottom of the processor then the blades can touch the surface during processing, and I suspect that is the cause of the problem.
     
  6. Dave Miller

    Dave Miller Member

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    It's just possible that the presoak dilutes any residual fixer on the blades Richard.:smile:

    I also sometimes use a presoak with thicker FB mono papers to get the paper to lay flat, but I've never found the need with RC papers.

    Let us know how you get on.
     
  7. wintoid

    wintoid Member

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    Well I made 3 prints tonight.

    Print 1 - I used presoak and also rewashed the blades of the already-dry Orbital. Result - Perfect
    Print 2 - I used presoak and took great care over the blades. Result - I got the line from one blade, but not in the middle, just the extremities

    Then I thought a bit and realised that when I wash my print in cold tap water, it arches upwards away from the base of the Orbital as it cools, so I thought perhaps if I heated the orbital a little before processing the print, it might arch the other way, away from the blades.

    Print 3 - No presoak, but did take great care over the blades. Warmed the whole orbital up with a soak in warm tap water. Result - Perfect

    At this point, I don't yet know if I've cracked it. 2 out of 3 is certainly better than I was doing before. I will continue experimenting.
     
  8. Dave Miller

    Dave Miller Member

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    If it's any help both my tray and developer are at 20 deg C at the start of processing.