[alt-photo] Re: Your Approach to Making Negs for Platinum Printing? Ideal Negative Contrast and Dmax?

etienne garbaux photographeur at nerdshack.com
Sun Oct 9 01:47:54 GMT 2011

Don wrote:

>Have you printed a Stouffers step tablet yet with the palladium/platinum
>mixture you plan to use on the paper you plan to use?
>Be prepared to exercise some elbow grease testing and then be prepared to
>ask questions.

Amen to that!

Everyone's process is different in alt photo -- your Pt ES will not 
be the same as mine because our solutions are mixed differently (no 
matter how hard we try to match them), you coat differently than I 
do, at a different temperature and relative humidity, your paper is 
from a different lot (or is a different brand), your exposure system 
is brighter or less bright than mine, and they are not spectrally 
identical, etc., etc., etc.  We can tell you that you should expect 
your ES to be around 2.0 to 2.4 for traditional Pt once you have the 
chemistry and exposure working reasonably well, but we can't get you 
closer than that.  You will have to do the measurements yourself to 
determine YOUR Pt ES (and it may change as you learn and get the 
chemistry and exposure working better -- it also may change randomly 
according to variables you have not controlled, which can be frustrating).

As far as process control goes, try to keep track of all 
variables.  Use distilled water for ALL solutions.  Stick to one lot 
of one type of paper (and be prepared to reinvent the process every 
time you change paper -- even lots of the "same" paper).

For sanity check purposes, assuming that you are using the 
traditional Pt process with 100% Pt (no Pd):

Expect a print Dmax in the 1.4 range for starters.  As you get the 
chemistry and exposure working better, and try some enhancements, you 
may be able to push this to 1.7.  This will give a print DR of Dmax 
minus paper white density in the image area.  I use  the smoothest, 
brightest paper I can find that is compatible with Pt chemistry, for 
a paper white density in the image area of around 0.06 and a print DR 
of Dmax minus 0.06.  I can reliably get a print DR of 1.54 (= 1.6 - 
0.06) from traditional Pt.

Expect a print ES in the neighborhood of 2.1 to 2.4.  I have observed 
them as high as 2.95.  I cannot recall ever observing an ES lower 
than 2.0 with traditional Pt (no "contrast agent," 100% Pt).

Frankly, I do NOT recommend printing any image negatives until you 
have the printing process under reasonable control using step 
wedges.  It is too easy to be distracted by image details (and often 
with an image there are no areas of stable density large enough to 
reliably measure).  I know it sounds geeky and not at all artistic to 
say you can do all of the densitometry/sensitometry with step wedges 
and then go out, expose one sheet of film with a spot meter, process 
and print the negative, and get a print that ranges from the print 
process's Dmax to Dmin -- but I submit that if you learn to do that, 
you will have a much better understanding of the materials and 
processes you use and a much richer toolbox to serve your artistic 
vision going forward than if you just settle on something that seems 
to work and leave it at that.  I commend Francesco for his efforts to do so.

Best regards,


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