UV vacuum box for pt/pd

Discussion in 'Alternative Processes' started by coigach, Nov 6, 2012.

  1. coigach

    coigach Member

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    I'm wanting to have a bash at pt/pd printing, and although I plan on using a digitally enlarged positives from my original film, I hope my question still stands and is within APUG's scope...

    I use both 6x7 and 6x17 panoramic medium format cameras. Because of the wonky size of the 6x17, contact frames are likely to be problematic, so I'm looking at a UV vacuum unit instead. (I use a big vacuum unit at the Print Studio for my polymer photogravures, and have come to appreciate the advantages of vacuum units).

    Do you think something like this would be a good option?
    http://www.exposureunits.co.uk/UV-Exposure-Units-With-Vacuum.html
     
  2. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    Those look fine. Just as a point of clarification, if you're doing pt/pd, whether from in-camera originals or enlarged (digitally or traditionally) images, you'll need a NEGATIVE, not a positive. Actually, the 6x17 size/proportion isn't that problematic for contact printing frames, if you have the right frame. I have a vintage (1920s/30s) 12x20 contact printing frame that would be just fine for making prints of that proportion, and I also have a similar vintage 14x17 frame in which I could do two at a time. But vacuum frames are nice, if you can find one you can afford and have space for it.
     
  3. coigach

    coigach Member

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    Cheers for reply.

    Re: positives - excuse my brain-dead typo. I use enlarged positives for my polymer photogravures and think that threw me after typing about photogravure's...! :blink:
     
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  4. jp80874

    jp80874 Subscriber

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    Is it possible that one of you is talking CM and the other inches?

    John Powers
     
  5. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    I'm talking both. If he enlarges from 6x17cm to whatever size he wants to make his final prints, a 14x17 inch contact frame would handle two prints at a time, or a 12x20 inch frame would handle an even larger single print.
     
  6. Davec101

    Davec101 Member

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    You might want to test out the unit before buying, when i started looking at these types of a units quite a while back i experienced problems due to the fact that the uv tubes were set at a fixed distance and could not be modified resulting in uneven expsoure and what seemed to look like some sort of 'uv burn' on the final print. there might be a way around this but like I said see if you can test one that would be best.
     
  7. coigach

    coigach Member

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    Thanks for this, very useful info. Do you remember which models you tested?

    It's unlikely that I'll be able to test equipment - I live north of Inverness in the highlands of Scotland, so things are a bit trickier...!

    Any advice on other approaches or options to consider? (Budget is a consideration, the vacuum box links I posted are my price range).

    Is there an ideal distance for the tubes?
     
  8. Davec101

    Davec101 Member

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    On that link you posted i tried the model at the bottom which is beige in colour.

    Ideal distance with my own set up, shown below is approx 9 inches, bulbs 1 3/4 inches apart.

    6088834755_5bb3e25cf2_b.jpg

    On a budget others options are to create a uv exposure unit yourself with uv tubes in a wooden enclosure, instead of using a vacuum use a heavy sheet of glass, will work upto 11x14 inches any larger you really need a vacuum unit to maintain sharpness across the print.
     
    Last edited by a moderator: Nov 7, 2012
  9. coigach

    coigach Member

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    Thanks again for info. Will now investigate the possibility of a homemade unit (well actually a made-for-me by a friend who is a joiner to trade!).

    Another question though, possibly very stupid, so be gentle :smile:.

    I lustfully looked the picture of your setup, looks fabulous.
    http://www.apug.org/gallery1/showimage.php?i=51980&catid=member&imageuser=7447
    But if the bulbs are at the top facing down onto the paper, how does your vacuum work??
    (I use a huge UV box at the Print Studio for polymer photogravures which has vacuum on top on a hinged lid, and bulbs below. The plates are placed face down facing the UV bulbs, and the top lid closed, then the vacuum seal is used to hold plate flush to glass).
     
  10. coigach

    coigach Member

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    Any ideas of sources for used contact frames this size in decent condition? - ebay not bountiful just now...! Am currently doing an internet search, but any extra suggestions appreciated. Am UK based, so anything from the US carries an import duty which needs to be factored into costs...

    Currently also looking into prices of new frames if cannot find decent used, but prices are pretty steep...
     
    Last edited by a moderator: Nov 10, 2012
  11. coigach

    coigach Member

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    Yep, it really was a stupid question - have answered it myself...! :whistling:
     
  12. Mark Fisher

    Mark Fisher Subscriber

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    Wouldn't it be simpler to either make a contact frame for the dimensions you want or have a piece of 1/4" glass cut and just use that? You could design a simple clamp (thinking plastic knobs plus fender washers) to hold the glass/neg/paper together.
     
  13. platebreaker

    platebreaker Member

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    I just skimmed this post but why cant you use the light source that you do your polymer plates one? Thats what I would do.
     
  14. coigach

    coigach Member

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    A couple of reasons - firstly the UV vacuum box is in a shared access print studio (intaglio, screen prints, linocuts, etc), rather than my own photographic studio, and the studio use policy and rules on chemicals in the shared space means it's a no-go. Secondly, it's lit by a single source, which others have suggested elsewhere might result in an uneven exposure? (This might not be the case, but as per reason 1, I haven't been able to find out)!
     
    Last edited by a moderator: Nov 12, 2012