Judy Seigel (jseigel@panix.com)
Tue, 15 Jun 1999 23:53:23 -0400 (EDT)
On Tue, 15 Jun 1999, Keith Schreiber wrote:
> Judy,
>
> A case is 12 bulbs isn't it? One of my units uses 10 and the other one 8,
> but I'm soon going to redesign that one for 10 or 12. If you don't need that
> many bulbs maybe find someone to split a case with.
Keith, my inquiries were nearly 10 years ago, and as we know, nowadays
that's more like a century. But at the time (and as I recall), a case was
20 bulbs. At least on the east coast. If you already mentioned this,
please forgive me -- I'm still a bit foggy & could be repeating what you
just said ... Voltarc told me that the AQA in the name stands for
Aquarium; these are made as bulbs to light aquaria, ie., fish tanks.
They suggested that I could buy them singly or in small numbers from an
aquarium supply store.
Finally I decided to go with the BL bulbs, because I already had some, and
they are *nominally* closer to the sensitivity of gum -- 360 nm, while the
AQA is 413, supposedly the sensitivity of platinum. But I taught a couple
of gum workshops at ICP with their AQA bulbs, and there was no difference
in effect that I could detect. If I'd known all about the numbers at the
time, I'd have made some comparison tests, but I didn't, and I didn't.
I think, though, that for gum printing, other variables -- such as mix,
pigment, thickness, color, etc. -- will lead to "spikes" of sensitivity at
wavelengths all the way up into the visible zone, so the 360 number is
more theoretical than real. (We talked about this on the list several
times in the long ago, or the almost long ago.)
However, it may not work the other way around -- it's entirely possible
that the spectral sensitivity of platinum is much more constant. Certainly
Bill Laven has found with HIS materials that the super-actinic 420 nm
bulbs are consistently "better" & faster [have I got that right Bill?] as
described page 42 of current Post-Factory, by the way.... though I gather
not YET in California, which is a place apart.
But speaking of spectra and spikes, if you can get one of the fluorescent
bulb catalogs from, say, GE, they have a "profile" of light output of
their various bulb types, from the low UV through the visible spectrum.
It's very interesting to see the range -- looks like a bunch of really
tall thin mountains in the diagram. (Hmmmm, that might be good to
reproduce one day, if I can ever squeeze out an extra 2 inches.)
My tests with Daylight fluorescents, incidentally, showed that they were
slower and MUCH more contrasty than the BL for gum. So it's entirely
possible that those 420nm Super Actinics, or the AQA, would be an
excellent happy medium for gum. However, truth to tell, I myself am hooked
TOTALLY on the vacuum frame, so I mostly use the NuArc with its sodium
quartz whatever bulb. I confess.
It's noisy & hot in summer, but... addicts are not creatures of reason. I
keep the BL's handy for certain tests and for emergencies, like when you
live in the country you keep flashlights & candles in case of power
outages.
> When I built my smaller unit about 6 years ago, the 24 inch F20T12/AQA bulbs
> cost $17.50 each. The 48 inch F40T12/AQA bulbs that I bought a month ago
> cost $15 each. That is about the same as the BLs that I got at Home Depot
> about 4 years ago (which they no longer stock BTW).
Keith, are you printing that large, or running several prints at a time???
cheers,
Judy
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