Re: Pt/Pd printing with various lights

[Clay Harmon <wcharmon@wt.net>]

Title: Re: Pt/Pd printing with various lights

For the curious:

I've taken one of Dick's workshops. Here is what the #7 mixture Pt/Pd consists of:

a drop ratio of 6 Pt/ 6 Pd/ 6 Ferric oxalate #1 (no potassium chlorate)/ 6 Ferric oxalate #2 for Pt(Bostick and Sullivan mix i.e. K-chlorate @0.6%) 

This is Dick's standard way of calibrating a light source for using his speed/contrast sensitometric curves. He also standardizes on platinoty
pe natural white paper and typically coats his test data with a puddle pusher. He is left handed, and loves Gilbert and Sullivan. His standard printing time is such that step #4 on a Stouffer wedge is the just barely lighter than maximum black. Using his curves and transmission density data from your negative, it is trivial to get a first print that is within about 10% of the 'perfect' time for that negative.

Sandy's data is very useful and relevant for those doing develop out platinum/palladium.
 I agree with him that while the absolute numbers will change depending on everyone's personal habits, the relative speed/contrast differences should not for develop-out platinum printing. Thanks Sandy.

Clay


on 5/9/02 6:58 PM, Eric Neilsen at e.neilsen@worldnet.att.net wrote:

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 t o 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 l ast 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.  

< FONT SIZE="2">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 -----
From: Sandy King <mailto:sanking@clemson.edu>  
To: alt-photo-process-l@sask.usask.ca
Sent: Thursday, May 09, 2002 12:50 PM
Subj ect: 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 energ y 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.

Fi rst, 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 enviro nment 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 u sed.  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 sour ces.  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 <mailto:sanking@clemson.edu>
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 o f 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 <mailto:sanking@clemson.edu>
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) 2 0 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   &nb sp;         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 dens ity 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. Ho wever, 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



--

--< BR>