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Sandy, The unsaid aspects of your work are
what make it undetermined. How long did it sit and in what state? Dry and
sealed? If so dried to what RH and sealed how? All of this may seem nit
picky, but the factors do give insight to those who know, and may educate those
that don't.
The type of glass used can produce differing
results for different light sources, so what type of glass? These all influence
the speed on contrast of platinum / palladium mixtures.
Does #7 have Pot Chlorate added? If so, does
it last for a day? Did you run a comparison with Dick and his SA lights or
Nu Arc unit? with equal parts Pt and Pd I would be quite surprised to find
solarization in the blacks. Why did that happen? I can expose for
very long times before I see a reduction of Dmax with a 50/50 mix.
What was your exposure times in minutes/seconds? If
they similar or quite different that too would be very useful.
I am not discounting your findings here Sandy, just
asking more questions. I mean you no flames, or ill will. Inquiring
minds want to know : )
EJ Neilsen
----- Original Message -----
Sent: Thursday, May 09, 2002 12:50
PM
Subject: Re: Pt/Pd printing with various
lights
Eric,
I am surprised that you find my tests too loose to "prove anything." If
anyone else at anytime has conducted tighter tests with a several different
light sources in platinum, palladium or with a combination of the two, please
tell me where I can see the results. Typically the information we get about
printing with different light source is purely anecdotal and involves no
attempt at all to provided control parameters. You know how it works. Joe Blow
tells us he changed out his Type A lights for Type B and now is getting two
stops more printing speed and more contrast. But Joe failed to mention that
this was purely subjective evaluation, or that he was using a new film and/or
developer, or that he also changed the ballast, or that he is now using a new
printing frame, or that he decreased the distance from the frame to the
lights, or that the old and very inefficient air conditioner outside had been
replaced with a more energy efficient unit, or that he really never kept any
exposure information at all, etc.etc.
In any event my tests were done to "find out something", not to "prove
anything." And since I have clearly outlined the parameters of my testing I
don't make any claims that go beyond the findings.
You have raised two questions about the validity of my testing. Since I
am not an experienced platinum printer I think it appropriate to discuss each
of these questions.
First, you describe the coating as of undetermined in nature.That is not
at all the case. Granted that I did not give the composition of the coating
but I noted that it was Dick Arentz' #7 mixture, the formula of which is given
in his book on Platinum and Palladium Printing. He describes the AB method of
platinum and this particular mixture is described on p. 60 of his book
Platinum and Palladium Printing as a mixture for printing with medium contrast
negatives. Since Arentz is one of the premier Pt/Pd printers in the
world and this book was published by Focal Press I assumed that this
terminology would have meaning for other Pt/Pd printers even though it does
not for me. It is described as a coating of equal parts of palladium and
platinum designed to print a negative with a DR of 1.35-1.40, a mixture that I
would think fairly typical of what many people use in actual practice.
Second, you questioned the reliability of the results because
coating was done outside of my own working environment and the testing was not
done until a day later. I am sure you are right in that the speed and contrast
of a material will change with time between coating and exposure and with
humidity. This was one of my own concerns when Dick and I initially discussed
running the tests Pt/Pd tests. However, after discussions with Dick he
convinced that this procedure would not interfere with the reliability of the
tests when the objective was to compare printing speed and contrast with
different light sources. The thinking was that although the speed and contrast
of the samples might indeed be different the change would be uniform.
I don't have any idea what tests with different mixtures of platinum and
palladium might show. I know from my own tests that the curves for palladium
and platinum are of different shape, even at the same ES, and there may
indeed be a difference in printing speed with light sources of different
wavelength depending on what particular salt or combination of salts was being
used. What I know is that I tested what appears to be a fairly typical
Pd/Pt mixture with very carefully controlled procedures and found that the BL
tubes were one full stop faster than the SAs in this test.
Sandy
Sandy, As
platinum and palladium have different response curves, you have been only
able to test an undetermined coating with three different light
sources. I would not make any conclusions about all platinum/palladium
coating based on these test. Since platinum and palladium are both
speed sensitive with regard to humidity, they indeed have been shown to
react to differing wave lengths to produce different yields, I find your
test to be too loose to "prove" anything beyond that all three react to your
lights with equal +/- results.
EJ
Neilsen
----- Original Message -----
From: Sandy
King
To: alt-photo-process-l@sask.usask.ca
Sent: Wednesday, May 08, 2002 8:14 PM
Subject: Re: Pt/Pd printing with various
lights
Eric,
I agree that if the purpose of my test had been to compare the
absolute speed of different processes it would have been best to coat,
dry, expose and develop all of the samples in my environment. However,
the purpose of these tests was not to determine the absolute
printing speed of the Pt/Pd material vis a vis another printing
process, but its relative speed with different lights. In that sense
I believe that the results of the test are very reliable. I made three
different test prints with each light and results were almost identical
for all three tests made with a specific light. If any one test had been
off with respect to the other two it would be reasonable to suspect a
difference in speed or contrast in the samples and that would of course
have invalidated the test results. Since this was not the case,
however, I am reasonably certain that these results are valid.
Sandy
Sandy, I
would think that a better test would be to coat them yourself.
Speed changes in paper and contrast may change to much sitting for a day
or more.
----- Original Message -----
From: Sandy
King
To: alt-photo-process-l@sask.usask.ca
Sent: Sunday, May 05, 2002 6:53 PM
Subject: Pt/Pd printing with various
lights
A few weeks ago I posted some
preliminary observations on the use of different UV sources with
Pt/Pd. As you may recall I exposed a Stouffer TP 45 step wedge
to paper coated with Dick Arentz' Pt/Pd Mixture #7, using the
following light sources: 1) 20 watt Phillips BL, 2) 20 watt GE BLB, 3)
75 watt URI Super Actinic, and a 1000 watt HID-Mercury
Vapor lamp. Today I read the densities of the tests and plotted curves
with Davis' Plotter program, with the following
results.
BL
BLB
SA* HID
Speed Point
2.5
2.4
2.3 2.2
Exposure Scale
1.31
1.36
1.23 1.31
IDMax
1.17
1.20
1.23 1.31
* I also tested the 20-watt Phillips Super Actinic tubes
and the results were virtually identical to that of the 75-watt URI
tubes.
*The HID-Mercury Vapor lamp was tested with a center
filter which reduces printing speed by about two full stops. Without
the center filter this lamp is faster than at least one full stop than
any of the other lights.
For those not familiar with the above terms, here is some
explanation of terminology.
The Speed Point indicates the speed of the material
and is expressed here in relative terms. The higher the number the
faster the printing speed. The values are in log units where each
value of 0.1 represents one-third of a stop, or 0.3 corresponds to one
full stop. Thus, the BL tubes turned out in these tests to be
one-third of a stop faster than the BLB tubes, two-thirds of a stop
faster than the SA tubes, and one full stop faster than the
HID-Mercury Vapor lamp (with the center filter).
Exposure Scale is the range between the minimum and
maximum density values required to print all of the tonal values. It
is also expressed in log values, with each 0.3 units corresponding to
one stop. An ES of 1.3, for example, corresponds to 4 1/3 stops. ES
relates to image contrast, the lower the number the higher the
contrast.
IDMax is the value that corresponds to 90% of maximum
black.
There have been quite a number of claims that Super
Actinic tubes are faster than BL and BLB tubes for printing in
platinum. My tests show the opposite. However, the SA tubes did
produce images with more contrast than any of the other
lights.
Just for the record I ran the tests three times and the
results were very consistent. Over 95% of all readings of the three
tests made with a specific light source were identical, and no
difference greater than log 0.02 was observed.
Comments and questions about these tests are
welcome.
Sandy King
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