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  1. #1

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    Paterson Orbital pre-soak calculator

    I've just bought a second hand Paterson Orbital print processor with the intention of developing BW 8x10 prints in it. The manual makes reference to the "pre-soak calculator", which I do not have. As I understand it, assuming you want to raise your temperature to 20C, and the room is say 18C, you let your chemicals be at room temperature, and pre-soak the tray/print for 30 seconds in water at a temperature greater than 20C, determined by the calculator. This is appealing to me!

    Does anyone have a pre-soak calculator from which they'd be able to give me a few examples of how to get to 20C, so that I have an idea what temperature to set the pre-soak at?

    Many thanks,

    Simon.

  2. #2
    Steve Smith's Avatar
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    I only use my Orbital for 5x4 negatives. For B&W prints, I don't think I would worry about a 2 degree difference. I never measure the temperature of my developer when using normal trays.

    For black and white I would always process at room temperature. The paterson Orbital was originally intended to be used for processing colour prints where temperature is more critical so I think the calculator is only really valid for colour.

    However, I will have a look tonight to see if I have my instructions. If I can find them, I will post them.


    Steve.

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    Thanks very much Steve.

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    I've just joined up and came across this thread. By coincidence it was I who invented the Pre-Soak Temperature Calculator for the Paterson Orbital Processor in the 1970s when I worked for Paterson.
    The temperature control system is pretty much as you have all described it except that it relies on a pre-soak of a large volume of warm water to bring the temperature of the processor somewhat above the temperature you want the solutions to be at. As you surmised, the temperature will fall gradually back down through the room temperature to provide a satisfactory average over the development time for a print. The subsequent solutions are not very critical as long as you give enough time. You can't easily overdo them! The Processor and the solutions should all be at room temperature. A minor issue is that you may need to raise the room temperature a bit if your solutions have to be very high, after all you can't very well pour boiling water onto your film or paper!
    I still have a Processor and have recently decided to revert to large-format photography just for fun and intend to process 6.5 x 8.5 inch film in it. I know the requirements for paper and film are a little different but I know a couple of photographers nearby who do that already.
    I have a copy of the original instructions but not the pale blue and white Calculator. Would anyone care to swap a scan of the Calculator parts for a scan of the instructions? I could repeat some of my original tests but it would save me a bit of bother!
    In any event, if I can answer any other queries on it I'm always glad to help.
    Regards, Pixal8

  5. #5
    Steve Smith's Avatar
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    Welcome.

    Quote Originally Posted by Pixal8 View Post
    By coincidence it was I who invented the Pre-Soak Temperature Calculator for the Paterson Orbital Processor in the 1970s when I worked for Paterson.
    It's a great design. A lot of us use them for 5x4 and 10 x 8 negatives now. I know they were intended for prints but were negatives ever a consideration when it was being designed?


    Steve

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    Quote Originally Posted by Steve Smith View Post
    A lot of us use them for 5x4 and 10 x 8 negatives now.
    Same here. Although I must one day do something about modifying the inside base so that the negatives don't stick to the bottom...

  7. #7
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    I regularly use a Paterson Orbital for processing my 5x4 film - I chose to cut a piece of mesh (as used on drying screens) to sit in the bottom of the tray. This stops the film from sticking to the bottom and avoids having to indulge in putting globs of hot-melt glue everywhere.

  8. #8
    Steve Smith's Avatar
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    I just scored the bottom of mine with a knife. It was the easiest method and I'm sure it could still be used for prints. I haven't tried prints in it yet but I might give it a go.


    Steve.

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    I can state that the idea of processing film in the Paterson Orbital was never suggested. It just goes to show what an inventive lot you large-format users are!
    My first thought today, when starting to read the point about film sticking to the bottom, was whether a series of small bumps would avoid the partial vacuum under the sheet but I then read on to see that you've already sussed it. I think the use of blobs of hot-melt glue is genius and we could have done with your brain at Paterson! My concern would be that any texture mustn't cause scratches on the back of the film. I wonder, though, if it really matters if the film does stick. It certainly doesn't matter with prints and the only issue is if solution is retained around the paper or film and causes contamination of the next solution.

  10. #10
    Steve Smith's Avatar
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    Quote Originally Posted by Pixal8 View Post
    I wonder, though, if it really matters if the film does stick. It certainly doesn't matter with prints and the only issue is if solution is retained around the paper or film and causes contamination of the next solution.
    It doesn't matter if you process it emulsion side up. All that happens is that the anti-halation layer doesn't get washed off properly so it needs a separate wash afterwards. This is exactly how I did my first four sheets before I read about the scoring/glue blobs solution.


    Steve.

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