Proper uv etc for Silver Chloride paper (azo)

Discussion in 'B&W: Film, Paper, Chemistry' started by herb, Nov 15, 2006.

  1. herb

    herb Member

    Messages:
    376
    Joined:
    Jan 22, 2005
    Shooter:
    Medium Format
    I have been a fan, not necessarily a "disciple" of AZO, and have a pretty good stock of it. Plus, M&P are close to a new source.

    Enlarging on AZO has required a $2000 light head for a Beseler enlarger, which uses a lot of power.

    I have corresponded with a supplier of led's who can provide a uv led head.

    The question becomes: how much uv is required, and does silver chloride paper require additional wavelengths to fully expose?

    I am thinking that Photo Engineer or Tom Hoskinson can answer this, but I thought there might be another expert out there as well.

    Thanks
     
  2. BBarlow690

    BBarlow690 Member

    Messages:
    193
    Joined:
    Jul 20, 2004
    Shooter:
    Large Format
    Does it have to be UV? The glasses and precautions are a pain, even if they MAY not be totally necessary. If Michael and Paula print with a light bulb, why can't LED's be more benign? I don't actually know the answer, but I'll ask the question.

    I print Azo with a Zone VI Cold Light in a Beseler 45 with the lens and lensboard removed, head set way down close to the easel. I can also do a similar setup with my Saunders LPL/VCCE head. I get 45 second times, roughly, and I know the Saunders is 200 watts (I don't have the XL).

    An exciting project! Good luck!

    Bruce Barlow
     
  3. Donald Miller

    Donald Miller Member

    Messages:
    6,242
    Joined:
    Dec 21, 2002
    Shooter:
    Large Format
    The curves that Kodak posted for Azo showed that it required near band or UVA to expose properly. The light bulbs that Michael and Paula use are apparently emitting enough UVA to expose the material. I used the same bulb and it worked fine. However I did try exposing it with a F15T8BLB as well and it was also effective at a much lower wattage consumption. It may also expose, albeit slower, with light that is near to the UVA band (blue).

    I did purchase LEDs that emit at 395 nm (within the UVA spectrum) and I was unsuccessful in exposing Azo with them. I had them positioned as near as physically possible to each other (1/8 inch spacing) so I don't know that it would be possible to gain any more light output than what I was gaining from them.

    There seems to be a continuum of trade offs within a certain light spectrum. The continuum involves the light quality, the light quantity, and time. This would apply to the spectrum approaching UVB and also visible light in the blue range.

    Graded enlarging paper is also exposed very rapidly with UVA. I have no idea about the characteristics of the new paper that is supposed to be coming along. It may have the same spectral characteristics insofar as exposure and it may also be very different.
     
  4. Luc Cultor

    Luc Cultor Inactive

    Messages:
    7
    Joined:
    Sep 4, 2006
    Shooter:
    Large Format
    Hello!

    Azo as the first paper I ever printed. 6x9 negs from a Voightlander folder. I would put my trays on top of our washing machine and use the bare lightbulb with a pullstring for exposures. It was grand! I still have some of those old photos. I'm making my photographic comeback, after many years of distraction some might call a career. I was distressed to learn that Azo was killed off with the rest of the Kodak herd. I still have some of my old stock, and bought several boxes at ebay, so I can play for some time to come. I was printing with the bare bulb so familiar to me, but a friend suggested I try a 13 watt spiral BLB bulb instead. When I turned it on, I thought there's no way this is going to be bright enough. After scorching several sheets of paper, I was convinced, and settled down to make 20 second exposures. It's geat! Minimal power consumption, no heat, and sooo much easier on my eyes! I don't know about enlarging Azo, but it's great for contact printing.

    Cheers!
     
  5. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,781
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    I have used normal tungsten light which has a UV component. AZO paper has about 50% visible (blue) and 50% UV sensitivity, so you can use tungsten or flourescent lighting for exposure.

    I use very short times with flurorescent, about 2 - 4" but about 8 - 12" with tungsten.

    PE
     
  6. jgjbowen

    jgjbowen Member

    Messages:
    879
    Joined:
    Oct 13, 2003
    Location:
    Richmond, VA
    Shooter:
    Large Format
    Bruce, do you get 45 seconds with Grade 3 or the "new" Grade 2? I've tried this with the "new" Grade 2 and my exposures were in the range of 60 seconds for a straight contact print. Sometimes for a fine print, my times would be in the 120 second range.....way too long for my tastes.

    I had the opportunity to acquire an Azo head for $1,000 and grabbed it. My times for the "new" Grade 2 are 9 seconds with the Beseler head at the 19" mark as opposed to close to the negative. The other day, I had a fine print that needed "old" Grade 2 and the exposure was 5 seconds......much nicer than 45 seconds. Of course, I could always put a lens in and add some time if dodging and burning were necessary.

    Best of luck with this project.
     
  7. gainer

    gainer Subscriber

    Messages:
    3,725
    Joined:
    Sep 20, 2002
    UV causes cataracts. IR burns the retina. An arc welder without protective eyewear gets a double dose of injurious rays. Quartz-iodine Incandescent bulbs are capable of burning at higher temperatures than ordinary bulbs and produce greater amounts of both UV and IR. The IR will come through the glass bulb unless it has a filter. The UV is cut off by ordinary glass, but quartz is not ordinary glass. The business of protecting one's eyes can be a pain in the nether regions, but it's better to have one there than not to be able to see the photos you sacrifice them for.
     
  8. Donald Miller

    Donald Miller Member

    Messages:
    6,242
    Joined:
    Dec 21, 2002
    Shooter:
    Large Format
    I agree. Although this is off the main topic, my recent conversion of lamp in my enlarger to a 1000 watt lamp does have me concerned. I always wear my eye glasses when focusing and there is supposed to be a UV coating on the lenses. But the lamp is listed as producing UV although it sits above two heavy glass condensers and passes through three layers of glass before the condensers plus the lens elements....still, I wonder...
     
  9. sanking

    sanking Member

    Messages:
    4,813
    Joined:
    Mar 26, 2003
    Location:
    Greenville,
    Shooter:
    Large Format
    I was one of the first to experiment printing with AZO using the new spiral BLB tubes. The first test amazed me, in that the 13 watt BLB bulb I used printed faster, at the same distance, than a 90 watt RH-40 flood.

    One of the disadvantages of the BLB tube, however, is that the light output is not 100% when you turn it on. So in order to use the tube with success you need to turn it on for about a minute to warm up before exposing.

    Also, if you choose to use the BLB spiral tube I suggest investing in a pair of UV sunglasses. This will allow you to dodge and burn without fear of damage to your eyes.

    Sandy King
     
  10. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,781
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    Sandy, I've found that most tungsten and especially fluorescent bulbs put out enough UV to expose AZO paper in reasonable exposure times.

    PE
     
  11. don sigl

    don sigl Member

    Messages:
    306
    Joined:
    Jul 6, 2006
    Location:
    Durham, NC
    Shooter:
    Multi Format
    I tried printing Azo on my Gravure plate burner. It has a bank of 10 UV tubes. Exposures were less than 3 seconds for most pyro negatives. I ordered one of those spiral UV bulbs and thought I would stick it into my d6 condensor and see if I could enlarge 6x7 negs on Azo paper.
     
  12. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,781
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    We tried printing Azo with a UV contact printer used at the Formulary last summer and even at the shortest exposure time, the prints were severly overexposed. This was about 1/2".

    Of course, that was overkill, but we were just experimenting. Azo is very fast in the UV.

    PE
     
  13. don sigl

    don sigl Member

    Messages:
    306
    Joined:
    Jul 6, 2006
    Location:
    Durham, NC
    Shooter:
    Multi Format
    My gravure burner is home built, and I can adjust the light source to be up to 30" away from the vacuum frame. Even at this distance, the times were to short to be workable. About .5-3 seconds.
     
  14. sanking

    sanking Member

    Messages:
    4,813
    Joined:
    Mar 26, 2003
    Location:
    Greenville,
    Shooter:
    Large Format
    Ron,

    A couple of years ago I compared curves exposing, 1) with the 13 watt BLB spiral bulb, and 2) the R-40 flood with a UV cut-off filter. I basiclaly wanted to know if there was any difference in curve shape or contrast exposing with UV versus blue light. The curves were for all practical purposes identical. Is this typical of silver chloride emulsions?

    Sandy
     
  15. Will S

    Will S Member

    Messages:
    717
    Joined:
    Nov 30, 2004
    Location:
    Madison, Wis
    Shooter:
    8x10 Format
    I use 2 spiral blb with one spiral flourescent in the head of my Omega D2V to enlarge onto Azo. The times are a little long (40-60 seconds usually) and I have to use a larger aperture than I would sometimes like, and I had to get Nikkor enlarging lenses. But it works. Have to let the bulbs stay on all of the time. I just use a black card to cover the lens and I taped up the enlarger well to stop light leaks. But, it cost me about $40, not $1000 so I can deal with it. Mostly I'm enlarging from 4x5 and 645 too, though I have done a couple of 35mm.

    If two spiral blb can work I don't see why an led light source can't be used. I keep hoping someone will design and sell a head that will work on a D2 or a Besseler. Provided, of course, that the price is reasonable.

    Thanks,

    Will
     
  16. sanking

    sanking Member

    Messages:
    4,813
    Joined:
    Mar 26, 2003
    Location:
    Greenville,
    Shooter:
    Large Format

    What wattage spiral bulb did you use? These bulbs first came out in 13 watt size, but I recall seeing recently 30 watt bulbs for sale.

    Sandy King
     
  17. Kirk Keyes

    Kirk Keyes Member

    Messages:
    3,267
    Joined:
    Jun 17, 2004
    Location:
    Portland, OR
    Shooter:
    4x5 Format
    I forget the name of the effect, but with panchromatic films, red light exposures will give lower contrast than blue light exposure. It's not a huge effect, but it has been measured.
     
  18. Will S

    Will S Member

    Messages:
    717
    Joined:
    Nov 30, 2004
    Location:
    Madison, Wis
    Shooter:
    8x10 Format
    I got these. I'd be interested to switch to 30W though if they aren't longer/wider. It's a tight fit in the head as it is, though if I could find a much smaller source of white light I could probably get 3 blb in there.

    https://www.saveonlighting.com/i-sunlite_sl20_blb_bx-1091.htm

    Thanks,

    Will
     
  19. Photo Engineer

    Photo Engineer Subscriber

    Messages:
    25,781
    Joined:
    Apr 19, 2005
    Location:
    Rochester, NY
    Shooter:
    Multi Format
    Sandy, the wedge spectrograms of AZO and my chloride AZO substitute are pretty much symmetrical around the visible and UV regions. Mine is not spectrally sensitized. So, although I agree with Kirk, since these papers are not spectrally sensitized, what you observe appears to be normal.

    Spectral sensitization tends to decrease contrast, so when I sensitize the Azo emulsion to green light, it becomes lower in contrast. This agrees with Kirk's comment and my previous observations. It is not always true though, it depends on the dye. Some dyes do not decrease contrast.

    PE
     
  20. Will S

    Will S Member

    Messages:
    717
    Joined:
    Nov 30, 2004
    Location:
    Madison, Wis
    Shooter:
    8x10 Format
  21. Will S

    Will S Member

    Messages:
    717
    Joined:
    Nov 30, 2004
    Location:
    Madison, Wis
    Shooter:
    8x10 Format
    If I'm using spiral blb that are in the 300-400nm range am I correct that I don't have to worry about eye damage? These bulbs peak at 350nm (which is where AZO seems to be) so I'm thinking they aren't as particularly dangerous as UVB. I'm wearing my glasses too.

    Thanks,

    Will
     
  22. sanking

    sanking Member

    Messages:
    4,813
    Joined:
    Mar 26, 2003
    Location:
    Greenville,
    Shooter:
    Large Format

    Will,

    The spiral BLB tubes radiate most of their energy at about 360 nm. This is potentially dangerous to your eyes so I would recommend that you invest in a pair of UV glasses if you are going to be looking at the light a lot, as you would if contact printing with the bulbs, or in looking at the image on the easel in a projection printing system.

    Sandy King
     
  23. Will S

    Will S Member

    Messages:
    717
    Joined:
    Nov 30, 2004
    Location:
    Madison, Wis
    Shooter:
    8x10 Format
    Thanks! I may have to consider putting the uv bulbs on a separate switch and focusing with the white light only. It's too bad they take so long to warm up.

    Thanks again,

    Will
     
  24. sanking

    sanking Member

    Messages:
    4,813
    Joined:
    Mar 26, 2003
    Location:
    Greenville,
    Shooter:
    Large Format
    Will,

    Consider putting your enlarger circuit on a light integrator. That is what we do with plate burners, and in some cases with regular enlargers. The Metrolux timer, for example, is really a light integrator.

    Sandy