longer than normal print times for pt/pd

Discussion in 'Alternative Processes' started by echard, Feb 5, 2004.

  1. echard

    echard Subscriber

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    Hello, I was hoping someone could help me with my problem. I built a very low budget exposure unit for alt printing. I used flouresents from Kmart, took off the difuser and cut off the sides. I then replaced the bulbs with BL bulbs from bulbman. When I did this a couple of years ago my times were and acceptable 15 minutes or so. Then, last year, my times began to climb to 40 minutes to an hour. I can't figure it out. Then I realized that it may be the glass. I changed out my original print frame glass when it got scratched with glass from a glass company. Does anyone know if that could be the problem? Could it be blocking UV? It's cloudy outside and I'd really like to get to the bottom of this so I can print again.

    Many thanks,
    Echard
     
  2. Donald Miller

    Donald Miller Member

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    I can see a couple of things that may be involved. First you may be experiencing problems with UV transmission through the glass that you installed. Some types of glass transmit UV better then others. Typically glass effect in the UV spectrum that you are utilizing will not be as great as the far band UV would be for instance.

    The other matter that may be involved is that the fixture that you bought from Kmart has a ballast of some type in order to fire a fluorescent bulb. The bulb that you replaced it with (BL from Bulbman) may not be properly matched to the ballast in your fixture.

    Not knowing what wattage lamps that you are using, what the thickness and type of glass that you have installed makes it difficult to determine the cause(s) of your lengthy exposure times.

    Additionally there is the matter of negative density. If your processing has departed from your previous procedures and led to a greater negative density then times will be increased. A .30 increase in density will cause a doubling of exposure times. Do you have a densitometer or have access to a densitometer? That may be a good place to begin...unless you have already compared using the same negative for your equivalent exposure times.

    These are all things that I would check into in order to arrive at an answer. Good luck.
     
  3. sanking

    sanking Member

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    I think Donald's third suggestion is the most likely the key to your situation.

    I don't think the problme is the glass. There are differences in UV transmission of glasss but unless the original glass of your contact printing frame was a speciality glass that allowed tranmsision of more UV radiation (not likely since these types of glasses are fairly expensive and not at all common).

    Also, I also don't think the problem is a bulb mismatch, unless for some reasons you have a mismatch of normal output ballast with high output or very high output tubes. Again, this is unlikely since the difference in cost between normal versus high and very output tubes and ballast is so great that you would probably have picked up on the difference during purchase.
     
  4. echard

    echard Subscriber

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    Hmmm....I shoot8x10 Hp5 @ 200. Process in D76 1:1 for 13 minutes in JOBO CPA. These negs print fine on Azo #3. I used to over process my negs heavily and they printed fine with this printer set up. I don't over process anymore and my normal negs are now taking over an hour to print. That's why I began to suspect the glass. But, from what you all are saying it most likely isn't the glass. I don't have access to a densitomiter. All truth be told, I'd like to just by one of Edwards HO printers. Though, I'd rather sink the cash in more paper and pt/pd instead. Thanks so much for the help so far.

    Echard
     
  5. Jorge

    Jorge Inactive

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    Why dont you buy a plateburner on E bay? That is how I got mine and they are great for alt printing. I would love to have an Edwards HO unit, but at $1500 I can get 5 plate burners, or 1 plate burners and pt/pd supply to last me a long while.

    My times are a consistent 11 min, the bulb lasts a long time and you can dodge and burn if you feel the print needs it, that is what I dont like about the Edwards units, they are self enclosed.

    Good luck.
     
  6. Joe Lipka

    Joe Lipka Member

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    A suggestion from left field. How's your Pt/Pd chemistry? Fresh or not?

    You have not said if you are still getting the same quality of print, but only with extended times.
     
  7. cjarvis

    cjarvis Member

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    My exposure times are usually in the 25 to 40 minute range with a dozen 24" 20 watt BL tubes, but I know it is entirely due to negative density. I assume yours is the same problem.
     
  8. Donald Miller

    Donald Miller Member

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    Typically when one develops film to the density range required for Azo and Pt-pd the increased development will support more closely the mfg box rating on film speed. In shooting the film at 200 rather then 400 and not knowing where you are placing your shadows it would appear that your negatives are exposed more heavily then required. When you mention that you are printing the negatives on Azo grade three it would indicate that your negative density range is somewhere near 1.10 (that is what my tests on Azo grade three indicate). I would think that a likely scenario is that your negatives are overexposed and underdeveloped. Therefore you have a negative with greater then needed overall density and lower then optimal contrast.