From: Ed Stander (glassact@compuserve.com)
Date: 11/10/01-10:44:51 PM Z
Dear all:
Sandy kindly sent me two sheets of his cyanotype paper, allowing me to test
my olec graphic arts lamps against his. I used a 1000-2000-5000 watt
system set up 24 inches above a nuarc vacuum table. I also used two
different bulbs - a L-1250 and an L-1252, both of which are brand spanking
new. The L-1250 provides strong peaks at 400 and 420 nm, and a weaker
bump at 365nm (similar to a typical metal halide bulb, and not far from a
fluorescent). The L-1252 provides a stronger across-the board flat
spectrum. Both spectrums can be viewed at www.olec.com for comparison
(look under spectromatch).
The L-1250 bulb set to 1000 watts gave a good exposure after 20
minutes, as Sandy suggested it would. Step 1 and 2 of the Stouffer tablet
are dark, and 8 distinct steps are present. A reading on my Blak-Ray
Ultraviolet meter (recently calibrated at 365 nm) provided a value of 1000
microwatts/square cm during the exposure.
This is all as it should be.
The neat thing came when I replaced the L-1250 with the L-1252 wide
spectrum bulb, again used at 1000 watts. This bulb pegged my poor UV
meter at 6000 microwatts/square cm. Further, an exposure time to four
minutes gave a result identical to the L-1250 at 20 minutes (ie: 8
distinct steps commensing from max blue at step 2). This suggests that I
should be able to make a cyanotype in 30 seconds with the system running at
full brightness. Pretty neat.
So you see - metal halides are not all the same. Some are a little
more so.
Cheers, Ed Stander.
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