Platinum Sun Exposure and Split Back Frame

Discussion in 'Alternative Processes' started by gbenaim, Jun 24, 2007.

  1. gbenaim

    gbenaim Member

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    Hi All,

    While figuring out how to get some bl bulbs together in my part of the world, it occurred to me that maybe using the sun wouldn't be so unreliable if you just use a split-back frame. I'm guessing this is how it was done back in the day, of course. Once you get a feel for how a well exposed print looks, it shouldn't be too hard to repeat, sort of like DBI. So I'm curious what kinds of problems people have had when trying this approacj (I live in a very sunny area, even in winter, btw).
    Also, are 2 18W BL bulbs enough to expose an 8x10 platinum print, or do I need more power? And finally, does platinum paper fog over time? Someone is sending me some old Palladio paper, and I wanted to know if it's worth it. Thanks,

    GB
     
  2. Monophoto

    Monophoto Member

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    You certainly can use the sun in a split-back printing frame.

    The conventional Pt/Pd techniques are developing out processes - that means that the latent image after the paper is exposes is almost invisible, and you really can't see much until you put the paper into the developer. The traditional wisdom is that a print is properly exposed when you see a hint of the final image, but I have never figured out exactly what a "hint" is.

    You might want to look into the ziatype process. That is also a Pt/Pd process, but it is a printing-out process - the image forms directly during exposure, and the chemical step is primarily a fixing step. Ziatype would seem to be a natural for use with the sun.

    As to the number of bulbs you need - ideally, the bulbs should be 4-6 inches away from the paper during exposure. And of course you need enough bulbs to be able to get even illumination across the size print you are making. If you attempt to get by with fewer bulbs, and increase the paper to bulb distance to even out illumination, your exposure time will increase greatly.

    If you are using black-light tubes, it may be possible to make 4x5 inch prints with only two tubes. I would be concerned that if you align the bulbs close enough to the paper to get reasonably short exposures on 8x10 prints, the illumination will be uneven.
     
  3. TheFlyingCamera

    TheFlyingCamera Membership Council

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    You really need four BL tubes to adequately cover 8x10, but you can squeak by in a dire pinch with three. The risk with using the sun as an exposure medium is that the paper will get too hot while exposing. As pt/pd paper dries, the exposure time begins to shift, and image quality will degrade. You can guesstimate your exposure time if you leave some sloppy border outside the negative area because you can watch the color/density shift of the borders. When your borders are a uniform dark gray/gunmetal color, you're good to go, regardless of how much ghost image you do or don't have under the neg. If you over expose, you'll see the borders revert to this grainy blotchy texture, instead of being uniform. Depending on where you live, what time of day you try to print, and the weather, this exposure time could be anywhere from a minute to an hour. If your exposure times are too short (under 3 mins) it is hard to adjust the print if you look at it and say, "That needs to be a half-stop darker". Also, with too fast printing times, your margin between a half stop darker and overcooked could be too short for you to accurately control.

    If you've got the old palladio paper, it would be worth a try, but I would first humidify it before printing. Get a large tray, fill it with steaming water, and pass the paper over the tray until it gets limp to the touch. To make sure this humidification gets into the core of the paper, you may need to do this several times. You can do this in subdued room light. When your paper is nice and humidified, print with it immediately. Depending on how old the paper is and its prior storage conditions, it may well be fogged. But then again, folks are printing on Azo made in the 1930s successfully, so this may work as well.
     
  4. dpurdy

    dpurdy Subscriber

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    The paper might get too hot in the sun?!! I have done a lot of sun printing and I don't notice the paper warming up much at all. Maybe because it isn't generally that hot in Oregon. I also have a printing station set up with four! 275 watt UV curing lamps. The print can get much hotter than in the sun, yet I have had no fogging problems.

    When I print in the sun I make sure to set the print facing square to the sun. I guess that is obvious. Also the color of the black can turn different shades in the exposure from the same print depending on the amount of moisture left in the paper. Plus judging by the black border would assume a very consistant negative density in your production.
     
  5. Jim Noel

    Jim Noel Member

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    Fluorescent tubes produce an amazingly diffuse light pattern. Placement of the UV tubes 4-6 inches from the printing frame was proven unnecessary by Judy Siegel. In one issue, I believe the ninth, of the Post Factory Journal, she did a test which showed that regardless of this distance banding is not evident. For the final part of the test she blacked out every other bulb and laid the paper directly on the tubes - there was still no banding evident.

    Two tubes will work, but printing times may be excessively long. Since there is now a 100 watt screw-in fluorescent tube available, the most economical method of building a UV box for 8x10 is the use of one of these. The ballast is built in thus reducing wiring and cost. Printing times should be reasonable.

    As for Pt/Pd edges reversing (solarizing) with long exposures, I have never seen this with the combination. It is not uncommon when printing Pd alone. If such prints are developed in potassium oxalate the solarization is often visible in shadow areas.
     
  6. gbenaim

    gbenaim Member

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    Jim,

    Is that a regular or bl screw in 100w bulb? If regular works at that wattage, then that's easy. Otherwise, where do you get the bl screw in? Also, is that actually 100w, or equivalent to an incandescent 100w?
     
  7. Jim Noel

    Jim Noel Member

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    It is listed as 100 watt in the same listing which lists 18 watt. So I believe it is 100 watt.
    Check the listing on the bulbman site.
    Jim
     
  8. z-man

    z-man Member

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    BLACK LIGHT URBAN MYTHS AND OTHER BLAHBLOGERY

    YOUR POST IS A BREATH OF FRESH AIR RE THE IDIOTIC USE OF 20+ BL LINEAR BULBS IN OVER PRICED AND BRUTE FORCE OVER ENGINEERED 200 POUND "UV EXPOSURE UNITS"

    i guess it's time for " those who know to tell those who don't"

    there are a multitude of uv cfl screw base self ballasted bulbs in 100+ watt BUT YOU WILL PAY $40 + FOR IT

    i use the uv led screw base units myself-no heat and 8 min exp time at 6" on blueprint paper-a single 28 led screw base will cover 4x5 at that distance-at 12" you get 8x10 cover and 15-20 min exp

    a properly designed linear unit of approx 3x4 ft wil only need 4 20 watt bl bulbs to give good coverage and reasonable times

    i used to custom build them but that was for commercial shops who had to make a living for their employees, so they knew what they needed and were'nt guessing

    vaya con dios
     
  9. gbenaim

    gbenaim Member

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    Z-man,

    Where do you get the led screw base UV units, and do you use just one 28 led? I'm not in the States, so the KIND of store, rather than a company's name, might be more useful. Electronics stores rather than a Home depot type place? Thanks,

    GB
     
  10. Ian Leake

    Ian Leake Subscriber

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    Can you post a link to an example? I may have to build a new light box, but if you can make my life easier then I'll be forever grateful :smile:
     
  11. z-man

    z-man Member

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    uv led screw base supplyer

     
  12. z-man

    z-man Member

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    can't post links-how about i list some?

    so how grateful is grateful???how about a 5x4 norma or a halfplate arca c line pro???

    better yet a halfplate gandolfi variant

    oh yes, you want sources:

    blacklight.com; superbrightled.com; topbulb.com; bulbman.com

    led=no percptable heat; cfl screw bases do heat up but not much however they are heat senstive re self ballast so in the high wattage bulb multiple installations you will still need a fan

    more better to use regular 20w linear bl-a 4 bulb unit can get by with convection cooling if you think about your design- and you get 100w spread over several sq ft

    if you can stand $150 buy the elation "uv wash 125" and you got a 125w point source fixture that only weighs a couple lbs but it will heat up a small space and the bulb is at least $40 to replace

    try musiciansfriend.com or samedaymusic.com or any club or lighting supply

    chauvet makes similar and both make led units too

    vya con dios
     
  13. Phillip P. Dimor

    Phillip P. Dimor Member

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    I can tell you that here in South Georgia the frame will get _very hot_ in the sun. My Eastman Kodak contact frame is bleached. I can also print until almost 7:30pm. Real hot. I'm not a real Southerner, i'm from Massachusetts. In MA. I only had 1-3 months where I could print using the sun. So hot here. Did I say it gets hot?
     
  14. z-man

    z-man Member

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    printing times and the heat

    ppd-waht kind of times are you using with what materials? what influence does the heat have on your processes-we now know that you are being pressure cooked-what about your prints?

    vaya con dios
     
  15. mmcclellan

    mmcclellan Subscriber

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    I had one made in Kosovo along the lines of this:

    http://unblinkingeye.com/Articles/UVBox/uvbox.html

    Given that I could not buy black light bulbs there, I just went with plain flourescent bulbs and the results were okay. UV, of course, is best if you can get it.
     
  16. z-man

    z-man Member

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    IT WORKS FOR YOU AND LOTS OF FOLKS

    asalamu alekum mcclellan

    regular cool white linear flouresent bulbs where in use in lots of comercial shops that i worked for or with -since the output of uv is not as high as uv bulbs the times are longer

    8 ft cool white bulbs are cheaper than 4 ft because so many are made and sold and they and 4ft are available eveywhere-since both are cheap and available -they are the bulb of choice in many commercial shops-i used them in the 60's if the very hot uv bulbs then available where a problem with a particular process

    in the 90's i worked in a fine arts silkscreen shop producing limitd edition signed serigraphs as large as 4 ft x 6 ft

    a bank of 8ft cool whites in a large bench was the light source-any of the shops a knew of allways had the light source so that you put the matereals to be exposed on top of the glass or plastic surface-since glass blocks uv usually an opal plexi was used but i don't think that the difusion was really needed since i worked with units made with clear glass

    a sun tan bed would do a spectacular job and i see that brits get used facial sun tan units and they are very succesful for them-philips makes the ones that are so common in britain-the lack of sun in britain is why they are so plentiful there

    i use cfl uvs because they are easy to get and cheap and self ballasted-i am changeing over to screw in uv leds-no heat no power draw

    thanks for the link- i had lost it and couldn't get back there-i think that the unit for printed circut bds is the most important because it show that you don't neeed as many bulbs as most think

    wa salam

    vaya con dios
     
  17. Phillip P. Dimor

    Phillip P. Dimor Member

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    z-man, it's van dyke brown with an occasional cyanotype. Nothing intensive. My vdb exposure (in direct sun) is about 1 to 3 minutes. My problem is overexposure which turns the tones to a very warm orange tone instead of a deep brown/black.

    The heat doesn't seem to bother the prints so much but I've read a bit about humidity and vdb. A bit of humidity helps with dmax? I wouldn't know, I do coat right before use.

    oh, and z-man, thanks for the heads up on the elation uv-wash and dj blacklights in general. I never thought about that. And those led ones look neat too.
     
  18. z-man

    z-man Member

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    van dyke orange?

    philip

    my experience with vandyke: orange is natural after water wash-fix changes to brown-if you use commercial fixer can bleach back brown to orange-are you using plain hypo? must be one shot or will not fix completely to chocolat brown-no exposure effect on color in my experience

    get some commercial blue print paper-sun print refill from freestyle same thing -this is very consistent and get exposure time from that as a constant

    i went up to boston to work for 6 yrs and froze my skimpy butt off-4xfat goose down ankle length hood trimmed in wolf fur coat i bought up there to survive has never been out of closet since i got back to nyc-watched brazilians come in the summer and never make it thru winter- can see how you are suffering in reverse situation

    vaya con dios
     
  19. platinumphotographer

    platinumphotographer Member

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    platinum prints do not heat up being exposed to the sun

    In fact, I think sun printing is the coolest way to print a p/p print. Mercury vapor is very hot and flourescent bulbs less so.

    Sometimes I found gum bichromate under mercury vapor got too hot.

    Gary Auerbach
    platinumphotographer
     
  20. platinumphotographer

    platinumphotographer Member

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    I think the sun is the sharpest point source light you can use. GA
     
  21. Phillip P. Dimor

    Phillip P. Dimor Member

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    z-man; never realized the hypo was one-shot :sad: that might have something to do with it.
     
  22. gbenaim

    gbenaim Member

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    Gary,

    I'm curious how you use the sun for plat printing. Do you use a spli-back frame, or do you judge exposure by the dark area around the neg? How consistent can you be? Thanks.
     
  23. TheFlyingCamera

    TheFlyingCamera Membership Council

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    You can use the split-back to judge exposure. A better gauge though is the borders - what shows up under the negative as a phantom image will vary widely from negative to negative, so guessing from the amount of phantom image is not a good starting point, unless you are printing a negative that is a known quantity. Once you get the borders to a certain look, the print is probably in the ballpark of where you want it to be, and if the first print isn't just right, it will most likely be within a half stop to a stop of proper exposure.
     
  24. RobertP

    RobertP Member

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    I use a point light source.(NuArc 26 1k). But I must say that some of my best looking prints were made with sun exposures. When using the sun I use a split-back frame and do both, watch the edges and the latent image. You can pretty much nail it on the second print if there is not a lot of dodging and burning involved. What makes a point light source nice is the light integrator that allows you to really dial in the exposure times that you can record and keep with the negative for future printing. The sun will vary, naturally, so every day could and probably will be different. At least it does with the lake effect weather we have here on the great lakes.