Curves for 9900 strong enough to avoid fogging with Pt-Pd?


Hello again,

I have read a post from Harris where he talked about some fogging problems in the unexposed areas of coated paper, and I had a couple of questions related to the answers which were given…

I am using a Metal Halide Lamp of 4000 W, and normally print with Pd and Pt in a 80-20% ratio. As I am using Pt, I fear I cannot use Na2 as contrast control measure in order to avoid fogging. However, some other printers told me than when using Pt too in the emulsion, the risks of fogging are quite limited… I would like to avoid using the A+B method for contrast control, since the graininess I obtain with it is not something I like…

What I would like to know is whether when printing with Pd and Pt and no restrainers at all, it is normal to obtain fogging when using the current PiezoDN curves? (assuming no stray light is present in the darkroom when working). I ask this because I read the answer of Walker, talking about the release of a new set of curves “for metal halide burners”, which made me think users like me should be using a higher density negs to really block out the brightest highlights?

Another question would be: When these new curves will be available, will their increased density only affect the last patch of the calibration target? In other words, will we have to re-linearize all papers again or they will only make sure the last patch is for sure totally white?

Thanks for the clarification, and for any clue about when these new curves might be available!

Warm regards,



Harris’s fog problem was with one paper - Hahnemuhle Platinum Rag. (Please correct me if I’m wrong about that.) There is also nothing inherent in a metal halide light source that would cause fog as far as I am aware. I am not currently using one, though I have in the past, but I never experienced such an issue. Mine was a 1500 watt unit though, not a 4000W like yours, or a 5000W like Harris’s, so I may be wrong about that.

If you have, or have access to, a transmission densitometer check the maximum density of your negative. I was getting about 3.2 - 3.3 UV density (slightly lower optical density) with K6 Selenium inks on a 1430, and am now getting slightly over 4.0 with K7 Carbon inks on a 3880. Anything over 2.5 or so should be sufficient.

Here are a few comments regarding the chemistry:

  • You are correct that Na2 is incompatible with the standard platinum solution
  • Use of the standard platinum solution does NOT have any significant effect on fog
  • Use of the standard platinum solution DOES have an effect on print "contrast" (more correctly referred to as Exposure Scale), but it is very slight at a ratio of 80:20 Pd:Pt. Probably about 0.05 density. At 50:50 it shortens the exposure scale by about 0.15.
  • In my experience with the A+B method of contrast control (potassium chlorate in B), grain problems only occur in ratios where there is more B than A.
  • Since you would be using B only to eliminate fog, you would be using the minimum effective amount which going to be something in the neighborhood of 11+1 (A+B) or less.
  • Another method, if you are using potassium oxalate developer, is to add sodium dichromate to the developer. I can go into this in more detail if you are interested.
  • Yet another method is to add hydrogen peroxide to the coating mix. Unfortunately, H2O2 degrades fairly rapidly so it is next to impossible to know how much to use and to get consistent results.
Yes, you need to relinearize any time you change any major factor in your process. That is if you want perfect, or close to perfect linearization.


We developed this curve internally for strong metal-halide lights.

It has extra density.

Will update the installs when I have time (and in an organized fashion).

This will not always fix fogging (as explained by Keith) due to chemical and darkroom issues.



Dear Keith

My issue of fogging happened both on Berggar and Hahnemuhle paper… for Berggar paper, the fogging is less but still exist…for Hahnemuhle is more serious. by using the Na2 method…all issues are gone!! thank you very very much for your teaching!!!

KEITH…YES…YES… i would like to learn more about sodium dichromate adding into potassium oxalate since i honestly do not want to use Ferric oxalate B (contrast control)…and my concept and experience maybe same to Rafela…it looks grainy and not easy to coat on paper…

I have ordered some Ferric oxalate contrast solution from B&S just in case i experience fogging on Pd+Pt prints… (i need to do this coz i have completed my Pd Na2 linearization and i am very happy with it after using Keith’s Na2 method)…

Keith, do you have any research or past data to show me the general look and feel of Pd/Pt print using different proportion of Pd/Pt… say 80%/20%, 70%/30% so that i can have a guideline to start my Pd/Pd linearization??? If you have one…would you mind sharing with me…? I just want to start another linearization exercise in the coming few days so that i can produce some platinum palladium prints : )

I really want to see the difference…but i believe the tonal range will be shorter if i am correct.



Dear Keith,

Thanks for your thorough and really enlightening answer. You are really fantastic, thanks for your prompt answers (to me and everybody else on this forum, by the way).

I was thinking about the use of dichromate to be mixed in small proportion to the developer… Which is the way you use it when it is only for eliminating the fogging problem with Pt-Pd prints? I would be really interested in knowing your views…

Thanks again for your help Keith and Walker,




I thought I had written up something about using the “Dichromate Method” of contrast control, but I can’t find it at the moment. There is a very brief description in Dick Arentz’s Platinum & Palladium Printing if you happen to have a copy. It’s on page 61 of the first edition, and 60-61 of the second. Here is a link to the relevant pages from Google books.

Since all we need in the context of digital negatives is one strength, the minimum, you can disregard all the stuff about different contrast levels. That is only for printing original in-camera negatives directly.

You need to make up a small bottle of 50% Sodium Dichromate. 100ml will probably last you forever, so let’s use that as our volume.

  • Start with 80ml of distilled water. Dissolve 50gm Sodium Dichromate. Add distilled water to make 100ml.
  • Add 1 drop of 50% Sodium Dichromate per 200ml of Potassium Oxalate developer. (Note: This method only works with Potassium Oxalate.) If you keep a 1 liter bottle of developer, that would be 5 drops. As your developer volume diminishes from use, you will replenish in 200ml increments adding 1 drop of your 50% sodium dichromate per 200ml of fresh developer.
  • As you probably know, Potassium Oxalate does not go bad (unless it somehow gets contaminated) so you never have to discard it. Just keep replenishing as needed.
I used this method from sometime in the mid-late '90s until I moved to New Mexico 12 years ago. At that point I switched over fully to the Na2 method.


Both the Dichromate method and the traditional A:B (potassium chlorate) method are compatible with the use of the standard platinum solution as well as the standard palladium solution. I haven’t used the traditional method since the '90s, but I never had grain problems unless using ratios in which there was more B than A, which was not uncommon when printing large-format film negatives, but should never be necessary with digital negatives. I also used it at half the strength (0.6% rather than 1.2%) of what Bostick & Sullivan sell. Even with straight palladium there was too big of a jump between contrast level 1 (12:0) and level 2 (11:1) for my liking. If you have the B&S Ferric Oxalate #2 with 1.2% chlorate, you might want to try diluting it to 0.6% by simply adding an equal amount of FO #1. (Note on terminology: 1=A; 2=B.)

Regarding ratio of Pt to Pd, first be aware that in most of the literature Pt is listed first. IJM is listing Pd first in their naming scheme. It is really a matter of personal preference. A 50:50 ratio gives a fairly neutral hue in general, but it is also somewhat dependent on paper and developer. Some papers print warmer or cooler than others. Potassium oxalate is a warm tone developer, while ammonium citrate is cooler. Heating the developer also increases the warmth of the image hue.

I doubt you will be able to tell the difference between 20:80 and 30:70 ratios of Pt:Pd. I used a 25:75 ratio for the first 2 or 3 years that I was printing Pt/Pd until I realized that I wanted all the warmth I could get and went to straight Pd developed in hot potassium oxalate. This is one of many situations where a 4x5 Stouffer 21-step (or 31-if you prefer) tablet is invaluable in learning and studying the variations and permutations of the process. It is large enough that printing it is like making a small print, and the steps are large enough to be easily read with a densitometer or spectrophotometer. You will be able to see (and read) any differences in contrast among different Pt:Pd ratios. There is a visible difference between 50:50 Pt:Pd and straight Pd. It is somewhere in the vicinity of 0.10 to 0.15, probably closer to the former. As you increase the amount of Pd, it becomes harder to detect to a point where it is insignificant.

As a best practice, it is probably wise to determine all of your process specifics BEFORE performing your linearization. The changes may not be large but they are there. If you change from 100% Pd to 50:50 Pt:Pd, you would definitely want to relinearize. From 100% Pd to 20:80 Pt:Pd, you might be okay with an existing linearization, but it might be a little contrasty.

Hope this answers at least some of your questions.



Dear Keith

Thank you very very much for your reply. You always give us comprehensive answers!! THANKS!

I have studied your reply as above and will start doing some PT/PD print with 80%Pd/20% PT first…

I only have the small 31 steps Stouffer, which seems i may have to order a new 4x5 big ones…

Please give me a little bit more time, and i will show you some of my work in return for your patience and teaching… : ) … or you can see it as sharing with you have learning a lot from you! : )