Proper uv etc for Silver Chloride paper (azo)
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.
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!
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.
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.
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.
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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.
Originally Posted by BBarlow690
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.
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.
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...
Originally Posted by gainer
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.
Originally Posted by Luc Cultor
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, I've found that most tungsten and especially fluorescent bulbs put out enough UV to expose AZO paper in reasonable exposure times.