From: Sandy King (sanking@clemson.edu)
Date: 11/11/01-02:37:44 PM Z
Ed,
Thanks for the information from your cyanotype tests. Perhaps you can
correlate what you did to the tests I also ran last night with this
paper. I got the following result from my tests with the commercial
metal halide unit that I use, and the Stouffer TEP 4X5. I also tested
the BL bank at the same time.
If you will recall from a previous message I can use the MH unit at
20" from the exposing plane, in one of two modes: A) without a center
filter, which gives even light for up to about 11X14" size prints,
and B) with a center filter that evens the light out over a 23X29"
area.
I do not have a spectral distribution chart for the Venture 5K 1000
watt metal halide bulb that was used for the exposure but I know that
it is rated at 5200 Kelvin.
Test Data-- 20 minute exposure
Mode A -- First maximum black at step #8, last visible step above
paper white at step #16. This indicates an exposure scale of about
1.35, or nine steps. Since this step tablet is over-exposed by four
full stops, the actual printing speed to get maximum black on step #2
would be about 75 seconds.
Mode B -- First maximum black at step #6, last visible step above
paper white at step #13. Exposure scale is still 9 steps. This test
being overexposed by two and one-half stops, the actual printing
speed to get maximum black on step #2 would be just under two minutes.
By comparison, my bank of BL tubes printed as follows. First maximum
black at step #6, with last visible step above paper white at step
#16. Speed was therefore virtually identical to that of the MH unit
in Mode B, but the exposure scale was 11 steps, or about 1.65. In
other words, the MH unit gives more contrast by about two steps.
I am of course calculating actual printing speed based on the time
needed to get a maximum density at step #2.
Sandy King
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