From: Sandy King (sanking@clemson.edu)
Date: 10/26/01-10:44:11 PM Z
Hi Eric,
All of my tests were run at about 70F and 55% RH, which are my normal
working conditions year round in a climate controlled environment.
Carbon is very sensitive (in speed) to temperature and humidity, and
I suspect that Van Dyke is as well, but all of my tests are done at
or near the control temperature and RH described above.
Tell me more about the conditions of your tests with
platinum/palladium. Did you use a step wedge? How did you determine
speed and contrast? Was there a difference in contrast between the BL
and BLB tubes? Did you adjust the tests with the BL and BLB lights
for humidity?
Regards,
Sandy King
>Sandy, I tested BL and BLB bulbs for platinum / palladium prints. There
>was about a 20% drop in speed with the BLB bulbs ( 8 minutes BL vs. 10
>minutes BLB). It may be of note that platinum and palladium have different
>speeds based on humidity of the paper. You might run the test at different
>humidity and heat ranges to see if additional forces are at work instead of
>just light waves.
>
>EJ Neilsen
>
>----- Original Message -----
>From: "Sandy King" <sanking@clemson.edu>
>To: <alt-photo-process-l@sask.usask.ca>
>Sent: Friday, October 26, 2001 3:01 PM
>Subject: Actinic Light: The Urban Myths
>
>
>> As you may know from a previous post I am preparing material for an
>> article on actinic light sources. In preparing data for the article
>> I ran a series of tests today with four different exposing lights in
>> both Van Dyke and Carbon. The lights were:
>>
>> 1. URI Super Actinic 24" VHO (75 watts)
>> 2. 24" Sylvania 350BL (Black Light), 20 watts
>> 3. 24" GE BLB (Black Light Blue), 20 watts
>> 4. Metal Halide Lamp, 1000 watts.
>>
>> The exposing negative was a Stouffer TP 45 step wedge. All tests of
>> same process were on paper sensitized and developed together. I
>> repeated all tests twice to verify results.
>>
>> The three tests with the fluorescent tubes were all for 10 minutes,
>> with the printing frame at exactly 4" from the front of the tubes.
>> All of the tubes were allowed to warm up for five minutes before
>> beginning the exposure.
>>
>> The test with the metal halide lamp was done with an integrator set
>> for 150 units, or the equivalent of 2.5 minutes, with the printing
>> frame at 20" from the light.
>>
>> In the article I am preparing on this subject I plan to provide
>> curves and complete data for all of the tests. However, you may be
>> interested in some preliminary observations.
>>
>> 1. There was a huge difference in visible light between the Super
>> Actinic, BL and BLB tubes. The Super Actinics put out a very bright,
>> bluish/violet visible light, the BLs a bluish light, less intense
>> than the SA, and the BLBs a very pale blue light.
>>
>> 2. In a comparative sense carbon is about one full stop faster than
>> Van Dyke. However, both carbon and Van Dyke exhibited similar
>> response to the different lights, both in terms of speed and contrast.
>>
>> 3. No surprise but that the metal halide unit was much faster (more
>> than two full stops) than the other lights. It also produced greater
>> contrast.
>>
>> 4. No surprise that the 75 watt Super Actinic was much faster (by
>> over a full stop) than the 20 watt BL tubes. It also produced greater
>> contrast than the BL tubes.
>>
>> 5. The *Big* surprise for me was that the GE BLB tubes were also much
>> faster than the BL tubes (and of about the same contrast). In fact,
>> the 20 watt BLB tubes were even faster (by about 1/2 stop) than the
>> 75 watt Super Actinic tubes!!! I was really quite surprised by this
>> result because for as long as I can recall the urban myth has been
>> that BL tubes are quite a bit faster than BLBs. Which makes me wonder
>> if anyone else has ever actually made an apples to apple test
>> comparing the BL and BLB tubes? Or if folks have just been passing on
>> erroneous information?
>>
>> Sandy King
>>
>>
>>
>>
>>
>>
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