Re: UV exposure unit and sunlight vs. artificial light
On Sun, 14 Dec 2008, francis schanberger wrote:
The only exposure units I have used have been the black light tubes (BBL?) and a NuArc 261K. Judy, was this addressed in Post Factory? I may have misplace one issue. Any suggestions for a starting point?
Post-Factory #6 has a feature titled "Light Carpentry," in which several of us illustrate and explain our systems & strategies (Mirkowicz, Makris, Schramm, & Seigel) with diagrams....
But let me mention that whatever the merits, history, and romance of exposure by sunlight, in much of the world it's so variable -- according to weather, atmosphere, time of day, and season -- that accurate timing is unlikely. Of course many processes have gauges and test strips that can be exposed alongside for guides, but where precision counts, IMO it's still very iffy.
For something like platinum, where there's one right exposure, outdoors is most iffy. For gum printing, which has many adjustments by varied development and can always get another coat or 2 or 3, if electric power has been shut off by storm (natural, human or other), the sun (even open shade) will work.
As for Nu Arc with vacuum vs. blacklight bulbs --- don't get me started.... But, since you insist, I had a NuArc I'd paid some thousand dollars for 15 or so years ago, which was such a pain in the butt I sold it for (I think it was) $100 and good riddance. Not everyone will have a problem with the noise (my husband was sleeping -- or trying to -- in the next room), but everyone will sooner or later find the wires in the NuArc's top section conking out, corking off, short or long circuiting, or other... requiring (an expensive) service call, or several... a situation I encountered every few years -- under not especially heavy usage.
As I recall, the technician came from New Jersey, a neighboring state, and had a regular route through NYC... What if you're located in, say, Western Pennsylvania, or Oregon? If and when the bulb burned out, that was an expensive replacement, and in fact the vacuum was another pain, as it was so strong, it had to be dialed down, differently for different materials.
But the main reason for dumping the Nu-Arc was space -- it has a very large footprint, while the UV light box sat on a countertop.
There are plans available (not just from Post-Factory, but generally, tho I'm forgetting the name of the provider(s), for building a simple UV light box... My first one had blacklight fluorescents just laid on the table, with simple wood supports for 1/4 plate glass on either side. The next (and current) one was almost as simple, but supports for the glass are built in. The beauty of this one is that the negative/print sandwich goes face down on that glass, and another heavy glass goes on top, covered by a sheet of black vinyl. Then, if there's any question about contact, I put a jug or two of water on top of that... while an oversize paper can stick out on all sides. If a bulb burns out (none has yet) it would be about $13 (or used to be) to replace.
Those bulbs, BTW, generate so little heat, that if the construction is open at the ends, no fan or other ventilation is necessary.
Post-Factory #5 showed (and I quote) "an exquisite, yet strong and functional UV printer based on blacklight fluorescents and the cabinet-making skills of Don Bryant." (If Don is still with us he may reveal whose plans he followed, which I don't recall at this moment..)
Finally, the notion that the Nu-Arc is faster (as if 3 or 5 minutes for a gum print weren't fast enough) is wrong. For several years I operated both systems and could compare times. The UV bulbs were at least as fast if not faster. (I assume also, tho don't know for sure, that they use less electricity.)
Oh, and fuggedabout the BLB -- or "black light blue" bulbs. AFAIK, they're for party tricks, with a special coating that only emits whatever rays make colors look spooky... but they cost more and put out less light.