Re: Re: carbon arc lamp

William Laven (William_Laven@designlink.com)
16 Sep 1995 12:25:09 GMT

Earlier, as part of a post re: carbomps, Art wrote:

Also check out the spectral sensitivity of what your working with. When I
did this for dichromates I was surprised to find that it is more sensitive
to blue light than the UV that I had been lead to believe.

This picks up on an important issue which floated around in a post a few
weeks back, ie matching the material to the spectral output of the bulb. I
recently printed the same negative under uncoated blacklight flourescent
tubes (the kind many use which offer a moderately broad spectrum which peaks
at 360 nanometers) and under super actinic bulbs of the same wattage (which
have a very narrow output which peaks at 420 nanometers -- much bluer than
UV). The actinic bulbs printed the palladium MUCH faster (almost a full
stop). Now the actinics were also newer so some of the difference is
probably the different age (and therefore different output) but the drop of
power over time with flourescents usually never exceeeds 15% which means the
actinic bulbs are still MUCH fatser than the UV bulbs.

I will retest the bulbs using new UV bulbs and I'll also try it with a
platinum/palldium mix and have a freind try it with POP. More results to
follow, but the initial data suggests the superactinics are superior for
Pt/Pd (confirmed by Martin Axon, who printed Mapplethorpe's Pt's and designed
a Pt/Pd printer).

And a note about plateburners. They weren't designed for the long exposures
necessary for Pt/Pd and other non-silver materials. Check the fan often to
make sure its not getting dusty and unefficient since you may fry the guts of
the machine if it runs too warm.

Bill

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