Cyanotype exposure - appropriate light source

Discussion in 'Black and White' started by stefan|1, Jan 30, 2004.

  1. I need a way to expose 8x10 cyanotypes. A halogen lamp with the UV screen removed works but it takes about one hour for the exposure. What is the wavelengths the process needs (I'm using the "new cyanotype" method)? Would a "black light" flourescent tube work? Their output seem to be rated around 365 nm. Is that good enough? Any comments or suggestions for other routes would be appreciated!
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  2. I've never made a cyanotype, but from my understanding this should be correct for nearly any photographic material: the shorter the wavelength, the better, other factors equal. A plain white fluorescent would probably be better than the halogen you're using now; certainly better for the same number of watts consumed, because it produces much more light per watt and more of that light is at shorter wavelengths (blue and UV).

    Fluorescent UV tubes would be better still, because without the phosphors, they produce light almost exclusively in UV (they have filtering, in fact, to eliminate most of the visible light emitted by the mercury vapor arc inside the tube), and will produce far more of it per watt than a halogen source. If you're now using a 300 W halogen, you'll probably get similar exposure times with 50 W of fluorescent UV.

    Of course, you'll have to start over in getting your contrast right -- everything I've read suggests that the more UV in your light, the more contrast you'll see in the finished cyanotype.

    Meantime, you might try sunlight -- much cheaper than a big fluorescent fixture, and a lot more power (except that it's hard to come by in the far north this time of year).
     
  3. Hi Stefan,
    I don't think, black light sources are a solution. According to my experiences there are two options (besides buying extra expensive "alternative contact prints printer"):
    Sunlight. I did my first cyanos with simple sunlight. Unfortunately you should have sun, that might tan your skin as well in reasonable time. I'm located in Hamburg, and decided, I want to do cyanos for more then 4 months a year. If your name says, you're located in Sweden, it might be even less. Althougth in Summer, less then half a hour expo should do.
    I bought a facial solarium. Thats kind of small (approx 10x12") tanning bank with 3 or 4 tubes. 50 cm distance do with approx 10-20 minutes. Got mine for 20 Eus at Ebay.
    Have fun
    Martin
     
  4. Stefan. How far do you put your source?. It should be really close to the contact frame. The prints I made with a 300w UV discharge lamp, I placed the lamp at 30 cm from the frame (exposure time 15/30 minutes, although it depends on the negative). When using the 4 18w UVB(those are the fluorescents you should get if you want to use flouros) I place the frame at just 5cm from the tubes (same range of minutes).
    Blue skylight is a good source (giving times similar or longer to the artificial sources I use) increasing the contrast of the print.
    Sunlight is a Cheap fast way of making prints, but gives less contrast.

    Good luck
     
  5. Thanks for the suggestions. I did try sunlight which gave me a nice full exposure with about 10 minutes of midday January sun in Nashville, TN. I also tried to put the contact frame on top of my ligth table with two flourescent tubes in it and that gave me a decent exposure in about 20 minutes, but in retrospect I think a littel longer would not have been a bad idea.

    From some other reading on the web it seems that UV-A is what you want and UV-B and UV-C (shorter wavelengths) does not necessarily help.

    I was pretty happy with the exposure from the light table, but I'm concerned that the light being diffused so close to the contact frame is not the best thing for contrast - I'm imagining that ligth strictly normal to the contract frame would be the best way to fly.

    I am looking for a face solarium on the ebay as well, but nothing or yet :)

    Thanks again for the feedback. -S
     
  6. Go Here: http://unblinkingeye.com/ For articles on cyanotypes and an article about building a UV light source. If you are in the Northern climes, then you would be best served by having a consistent source of UV light year round. Sun prints are romantic, but if you want to produce work on a consistent basis you should have an artificial light source. The unblinking eye site will get you in right direction.
     
  7. A UV bank of BLB tubes will work fine for exposing cyanotype. BL tubes will print with slightly more speed. Both types put out prodigious amounts of UV radiation and will expose cyanotype faster than diffuse sunlight.

    There are some other good alternatives. See my article on UV light sources at www.unblinkingeye.com.

    Sandy King
     
  8. When I said UVB I was trying to say BL tubes. Not the ones used in nightclubs (that I think, are the BLB).
     
  9. The article (should I say treatise :) on unblinkingeye was extremely helpful - thanks Sandy for writing it and providing the link. Any thoughts on using a light-table for exposures? Is the diffusion bad for contrast? It is really convenient, but two 40W BLB lights will cost about $40 so maybe I'll try that eventually. I do like the idea of being able to generate consistent exposusures... Is the duration of exposure also a factor in what contrast can be achieved? Is there a difference if the light source is weaker but the exposure time is longer? Anyway - thanks again for the all the helpful suggestions.
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  10. I'm doing a cyanotype project for a school project. For a light source, I'm using a ring-shaped black light that screws into a normal socket which I got at WalMart for $10. I've done about 10 tests so far and the light source seems to work fine. A good exposure time that I've found is 60 minutes and that's with the bulb just a few inches off the contact printing frame. if you would like to see some of my results, go here.
     
  11. I used nothing for the sun for cyanotypes - not the new recipe, the traditional one. It can be a pain a winter, but let's face it, chances are that you don't have such a large volume to print, or urgent orders; I suppose the job can always wait one more week. The UV described above are OK, but the sun ultimately tends to give more (better?) contrast - many long time UV printers think that UV floods are useful, but that in the end, nothing beats the sun.
     
  12. I used florecent UV bulbs. About 10 of them a few inches away from the paper for about 5 mins. It was a table with the lights mounted to the bottom of the table top. Then it had a shelf right under the bulbs. It worked great. Very bright.
     
  13. Apart from estethics regarding the process itself, what are the advantages of a high-output source other than a faster exposure time? Is the contrast better? Does it matter if the incident light is very diffused (my lighttable) or should it have parallel incoming rays?

    I was assuming that brighter is better and parallel would be better than diffused, but some people seem to think that open shade is better than direct sun, and that goes against both of those assumptions.
     
  14. Another way to increase the contrast is by submersing your images after they have been exposed and washed in a bleach bath and then rinse them again before drying.
     

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