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The Effects of Pyro Stain by Bob Herbst 'In the beginning there was platinum and the world was void and without form. And then God said, "Let there be pyro", and it was good.' So maybe I am getting a little
carried away. Using pyro is not exactly a religious experience although some promote it with almost religious fervor. I have
But, blue filter readings of the pyro negative do not give a true indication of how much printing density is added by the stain in a platinum/palladium print. The blue filter is measuring blue light in the visible spectrum, not the ultraviolet light to which platinum materials are sensitive. Using an Aristo Platinum Printer as a light source, I printed both negatives in platinum/palladium with my standard mixture (60% platinum/40% palladium) and paper, Cranes Parchmont Wove. I included a Stouffer step tablet strip in each print as a reference to normalize the print densities of the negatives. The print time was adjusted such that step 5 of the reference strip yielded approximately a 90% black (zone 1) in both prints. I read the reflective print density of each step and correlated the negative density in the D-76 and pyro negatives to determine which steps resulted in the same print density. This told me how much printing density the stain added. The reflective density readings are included in the table in Figure 4.
However, the effect of the pyro stain becomes more pronounced at the highlight end of the scale. Step 5 of the D-76 print has approximately the same reflected density as step 2 of the pyro print. The blue density of step 5 on the D-76 negative is 2.06 with fb+f subtracted yet the blue density of step 2 in the pyro negative is 1.54, almost 2 stops less in the blue filter density. But since these two steps yield approximately the same print density, we can conclude that the pyro stain is adding two stops more printing density than the blue filter reading indicates! From this data, it appears that it should be possible to obtain a silver print of about the same density range as a platinum print from the same negative. We already know that the stain is adding two full stops of printing density in a platinum print at the highlight end of the scale over what visible blue light would see yet the added printing density at the shadow end of the scale is less than one half stop. Silver papers are sensitive to visible blue and green light. In variable contrast silver papers, blue light results in higher contrast, and green light in lower contrast. A good example of this is the Aristo VCL4500 variable contrast cold light head. It has two tubes - one blue and one green. By varying the amount of light from each tube, the contrast of the resulting print is controlled. The more blue light, the higher the contrast. The more green light, the lower the contrast. The yellowish-brown pyro stain tends to block blue light as shown by the higher density readings for the blue filter. It passes more green light as shown by the lower density readings for the green filter. Hence a silver print from the same negative will be of lower contrast for a silver based variable contrast paper since the negative is passing more green than blue light.  To test this theory, I contact printed the same two negatives on
a grade 2 silver paper. The reflective densities of the silver prints are also shown in the table in Figure 4. The data shows
conclusively that the pyro negative yields a print in both platinum/palladium and silver which can represent a subject with a brightness range of 9 stops. The actual print reflective
density range of the platinum/palladium print is only about 5 stops but the subject brightness range represented is 9 stops - from step 1 to step 19. The actual print reflective density
range of the silver print is about 6 stops and the subject brightness range represented is also 9 stops - from step 3 to step 21. Hence, both a platinum and silver print representing
the same subject brightness range can easily be made from the same negative.The same is not true for the D-76 negative. The subject brightness range of the D-76 negative represented in the platinum/palladium print is 8 stops - from step 3 to step 19. But the subject brightness range represented in the silver print is only 5.5 stops - from step 9 to step 20. Thus, the subject brightness range rendered in the platinum/palladium print and the silver print from the D-76 negative differs by 2.5 stops! This difference might be narrowed through use of much lower contrast grades of silver paper but the separation of values will be reduced. Split filter printing might compensate for this but now you are getting into more complex print manipulation. Another alternative is to reduce development of the D-76 negative to print better on silver paper, but then more potassium chlorate must be added to the platinum/palladium sensitizer resulting in more uneven tones in the print. Either way, print quality compromises are required if one wants to print both platinum and silver from the same negative developed in D-76 or other traditional non-staining developer formulas. This series of tests provided a few more insights into advantages of using pyro for platinum printing. Because of the additive density effects of the stain, much less potassium chlorate is required for the same print contrast in the platinum print than for a negative developed in traditional developers. Increased amounts of chlorate tend to cause grainy or coarse tones in platinum prints. Using less chlorate results in smoother tones and allows for better separation of highlights because the silver densities are not being pushed to the film's maximum limits. Some printers might consider this a disadvantage because since you are working in the mid-range of contrast grades with very little chlorate, you do not have as much latitude to reduce print contrast from a high contrast negative. But in my personal experience, I have rarely had a need to lower contrast in a platinum/palladium print. I usually need to increase contrast. Another observation from these tests is that my time and temperature combination for pyro development yielded a longer scale negative than D-76. As we saw in the print comparisons, pyro compresses the subject brightness range resulting in a print with 9 stops of subject brightness without overly compressing any one portion of the scale. Prior to running these tests, my experiences in photographing in cathedrals and the canyons of southern Utah showed this characteristic of pyro. I frequently exposed images with a brightness range from zone 2 to zone 11 and this range was accurately rendered in the resulting prints. I believe that adjustments to the development of a D-76 negative may be able to produce similar results although separation in the shadow values might be reduced. This area requires further investigation before any conclusions can be made.  As we discussed this project, Dick originally
thought that my tests could yield a conversion factor which could be applied to a pyro negative to compensate for the effects of the stain in printing. However, the amount of stain produced by pyro is
unique to each photographer's process depending on method of development, formula, dilution, development time, and degree of developer oxidation. Therefore, the data presented here can
only be used as a general reference on the effects of pyro stain in platinum printing. Each photographer must run his or her own tests for their own development process. From an artistic perspective,
this is one reason why I like pyro so much. Because the effects of pyro and its stain vary from user to user, it results in a more personal interpretation or unique signature of the photographer using it. This little research project as been a pleasant diversion and I hope it provides some insight into the effects and advantages of pyro in platinum printing. But it can not replace the pleasure of seeing images come alive in a good printing session. It is time to set aside the densitometer and resume my artistic endeavors. Here's wishing you good printing no matter what film developer you use.
My pyro formula is a variation on the original Wimberly WD2D formula originally published in Petersen's Photographic in 1978 and later re-published in Darkroom and Creative Camera Techniques. My formula and processing practices do not necessarily follow the philosophy of maximum stain/minimum silver. Stain is your friend but it can be your enemy in printing alternative processes. Too much stain can easily extend printing times to an hour which I find unacceptable. The pyro-metol formula is identical to Wimberly's WD2D formula except for the restraining agent in solution B. The formula is as follows: Solution A
This article is copyright 1998 by Bob Herbst. All rights reserved.
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been accused of being in the latter category. In
reality, I believe excellent platinum/palladium prints can be made from negatives developed in any of the traditional developers given that proper care is taken in controlling the development process.
But for me and many other photographers, pyro offers an array of advantages over traditional developers. I wrote of some of these in my article in the September/October 1997 issue of View Camera, "The Advantages of Pyro for Platinum
Printing".
Now you must understand that I have resisted the temptation
for many years to run detailed film/development tests complete with graphs, charts, and spreadsheets full of data. My educational background is in the sciences with degrees in
both physics and computer science. My photography is my art, which I pursue to add balance in my life. I base my photographic explorations on instinct and emotions and I
make a great effort to not turn my artistic endeavors into an analytical science project. So to take Dick up on his suggestion was quite a stretch for me. But in the end, I must
say I gained quite a bit of insight about my process, the effects and subtleties of pyro, and why intuitively, I have always felt it to be a superior negative developer for use in printing in platinum/palladium.
Originally, I included 1.1 grams of potassium bromide in
Solution B as a substitution for Kodak anti-fog which was called for in the original WD2D formula. I had difficulty obtaining sufficient contrast in the resulting negatives and
development times were exceedingly long. On the advice of Gordon Hutchings, I eliminated the bromide which solved both problems. I have not noticed any fogging problems after
a couple thousand 4x5 and 8x10 negatives.
The developing action of pyro and the associated stain effects are very sensitive to small variations in developer temperature. Pyro oxidizes more
rapidly as the temperature of the solution increases. If you tray develop, use a water bath around the trays. Without a water bath, a 68 degree solution will easily climb to 70 degrees during development
just from heat transfer from your fingers. If the air temperature in the room is higher than the developing temperature, the solution temperatures will gradually rise as well without a water bath. A
two degree increase in developing temperature can have a significant effect on total negative density for a pyro negative. The accelerated action of pyro on both silver density and increased stain is
additive in the resulting negative and therefore has an almost doubling effect as if the negative had actually been developed even longer. The increase in stain has the greatest impact for platinum
printing. Pyro does not oxidize as quickly in a full closed tank. The staining effects are less pronounced for the same development time which must be taken into account when developing roll
film intended for platinum printing in pyro. |
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