Very long print times

Discussion in 'Contact Printing' started by ColinRH, Dec 5, 2010.

  1. ColinRH

    ColinRH Subscriber

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    Reading other threads concerning UV print times for various processes it seems that my times are much longer than might be expected, particularly salt prints. They are at present taking anything up to an hour or more. The actual time is more as I have to stop every 15minutes for the contact printer and glass to cool down.
    I am using FP4+(PyroPMK) in a frame I made myself which has 6mm Pilkington Optiglass (expensive but, so I was told, has better UV transmission). It IS quicker than ordinary glass!
    Attached is a picture of my printer which I made and is fitted with 8 x 15w (total 120w) Philips F15 T8 350 BL UVa tubes. They are about 3inches from the frame glass which measures 11x14 inches.
    I am wondering if anyone might have some idea as to why this setup is taking so long to make a print. Should I remove the inner frame which supports the print frame; I don't really see that would make any difference. Another might be to have stronger tubes but that would, I'm sure, only heat everything up even quicker. I could use thinner glass but with the times I'm experiencing now, I can't imagine any great reduction in time would be achieved.
     

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  2. Guillaume Zuili

    Guillaume Zuili Subscriber

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    For POP for example my UV box was almost useless. Meaning VERY long time and low contrast.
    When set into the sun or even just cloudy day my exposure time was much faster and contrasty.
    You might try that.

    My 2 cents.
    :smile:
    G.
     
  3. Ian Leake

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    Hi Colin,

    I can't see an obvious answer, but it's not clear to me how your lightbox works so may I ask some questions about it?

    1) From the picture, it looks to me as if you're projecting the light upwards through glass. Is this correct? This seems like an odd design decision to me because if your negative is in a contact printing frame then you're introducing an extra (and unnecessary) glass layer.
    2) This may be a dumb question, but are you sure those are UV tubes? I ask because every UV tube I've seen in recent years has been black not white.

    Also, have you tried printing with another lightbox to get a comparison time? I'm half way across the country (Worcester), but you're welcome to use mine if the logistics work. PM me if you're interested.
     
  4. Jerevan

    Jerevan Subscriber

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    Along the lines of what Ian says, maybe the bulbs does not output the correct part of the UV spectrum? There is no point in using glass in the box itself. Even if it has good UV transmission, at 6 mm, that's pretty thick. Maybe it also contributes to the heat issues, if it doesn't allow air to circulate. It's enough to have the printing frame glass.
     
  5. Vlad Soare

    Vlad Soare Member

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    You could try a facial tanning lamp. I use one of these, which covers 8x10" with some room to spare (I believe it would cover 11x14", though I cannot guarantee that) and gives me exposures of about five to ten minutes with vandyke prints.
     
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  6. ColinRH

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    Thank you for your replies;
    Ian and Jerevan; the aperture above the lamps is simply an open hole, the only glass is in the frame which sits within the brass around the edge.
    Ian, I think you may be on the right track concerning the type of tubes. When I bought them I thought I had done enough homework and purchased the right tubes. They are marked as UVA but perhaps it should be the blue coloured ones you suggest which may be UVB (or something else). I shall go off now, make further enquiries and see how I go.
    Vlad; yes, I started with the facial tanning lamp also but thought I would build my own in the hope it would be better! Obviously not the case. It will be interesting to find the exact type of tubes fitted to the Philips tanner. Again, I'll go and check.
    Colin
    Ian, thank you for your offer and if things get seriously difficult I may well take you up.
    Colin
     
  7. Ian Leake

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  8. Allen Friday

    Allen Friday Member

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    My small UV unit has "black light" tubes--but they look white when not turned on. When turned on, they give that classic black light glow to white cloth. In my large unit, I have BLB bulbs--"black light blue." When turned off, they are a deep blue/purple color. Both types of bulb will work. In fact, the white colored "black light" is a bit faster than the BLB. So, long story short, the color of your bulbs doesn't really tell you about the UV content of the light.
     
  9. ColinRH

    ColinRH Subscriber

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    Thnaks again for your inputs.
    I have been reading Sandy King's article on UV tubes on the Unblinking Eye site again. For the life of me I just can't get a definite answer. He suggests that BL tubes (which mine are) are slightly faster than BLB, but not a great deal, and like you say Allen, they show blue when running. I have also checked supplier's spec charts where available and they only state that UV tubes peak around the 350-360nm area, undoubtedly they start and end elsewhere but it is not shown.
    I wonder whether the real bottom line is that perhaps salt prints need a different approach (read 'sunlight') than other processes. In Sandy's - and indeed other - articles salts tend not to be mentioned. I did use sun earlier in the year and found it satisfactory even on a bit of a cloudy day. Perhaps that is where I will have to end my search. I will find another process for winter.
     
  10. Vlad Soare

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    A friend of mine, who makes vandyke and salt prints and uses a facial tanning lamp like mine, says that salt prints do require longer exposures, indeed, but not overly so. His exposure times with salt prints are about twice the times of vandykes, which means at most twenty minutes.
    So it appears that your tubes may not be the right ones for this process. You say you've used a tanning lamp before having built your own. How were your exposures then?
     
  11. ColinRH

    ColinRH Subscriber

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    When I was using the Philips tanning lamp (which of course had 'white' tubes) I was only using the Centennial POP. They took about 35-40minutes IIRC. It was then that I decided to make my own printer in the belief that I could reduce printing times. By the time I had finished the box, POP was no more so I looked for something else and started making Argyroypes with Fotospeed's solution BUT with d***l negs. They took only 7 minutes. I have some solution left and will use it with FP4+ which I am using now. It will be a useful experiment. I am wondering if the film base is not as suitable for tubes as Pictorico.
     
  12. Ian Leake

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    Hi Colin.

    I don't do salt printing, but I can say with certainty that FP4+ film base is fine for UV processes.

    I did a platinum printing workshop a couple of weeks ago and the student brought some FP4+ negatives developed for salt prints. I can't remember the details of his times or process, but the salt prints he showed me were really good.
     
  13. Allen Friday

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    You also might look at your negatives. If they are exposed at the same EI you use for silver printing, they could be way too dense. I found this out when I first started platinum printing. I was rating my tri-x at 200 (the same as I shoot for silver). I now rate it at 400 or higher, depending on the development. In effect, I was overexposing the negative and I had to print through the extra exposure with linger times under the UV box.
     
  14. ColinRH

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    Allen you could be on the right track! I have not made a proper film/exp test(shame on me). It could be the cause, although the image looks OK this is the first time I've use Pyro so don't really know what they should look like. (I feel stupid even writing this!) I'm out of time for the next few days but will make some tests before I blow money on other more expensive alternatives - tubes.
    I WILL post my next trial results. Thank you Ian for putting my mind at rest about FP4+
    Colin
     
  15. ColinRH

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    Well,, I'm going to 'test' my exp/dev process over the weekend, so the question here is do I do it in the usual silver print way.
    1) make a neg for Z.I and do the normal test strip to find correct film speed
    2) with that information make a neg for Z.IX and dev to find best dev time?
    Two problems I have in mind is 1) I have read that salts can show separation up as far as Z.XI. If that is the case should I be aiming to find dev time for Z.IX or XI?
    Or am I making a simple process difficult?
    ALSO I have found that when I have had to extend the print time up to 40-60+ minutes (every 15 minutes has to have a cooling down time) I find the paper has a silver metallic finish! Might this be caused by the heat which builds up or too much silver solution? I use 0.4ml for a 5x4 image.
    Any information gratefully received
     
  16. Jerevan

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  17. ColinRH

    ColinRH Subscriber

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    Jerevan
    Thanks for the link; interesting but my main problem seems to be the length of time for printing. I have been doing some more tests over the weekend and 2 things seem to have been learnt;
    1) I need to put a fan on my printer as exposures are still going to be in the 25-30 minutes area and everything gets hot which I think is the cause of silvery-metallic metal apparently being formed on the paper surface.
    2) All my tests are empirical as I do not have densitometers etc, so it is a longish process.