Hahnemühle Platinum Rag - batch variation


My recent Pd/Pt prints have been muddy and lacked clear highlights. I’ve spent the past three weeks trying to get to the bottom of my fog problem.

As a test, I processed a fresh sheet of sensitized (50%FO/50%Pd/Pt) Hahnemuhle Platinum Rag paper, with absolutely no UV exposure. It turned ~30% grey immediately after development. The grey would stubbornly not change at all despite long soaks in three EDTA clearing baths. So, I further dimmed my LED lights, mixed new Ferric Oxalate, switched from brush to glass rod application, replaced the Ammonium Citrate developer, and all three EDTA clearing baths.

Still, an unexposed test strip turned muddy grey showing significant variegation.

Finally, as a last resort, I broke open a different, more recent package of 11x15" HPR and made a few new test strips. Voilá! The paper cleared instantly of all grey tones and yellow stain immediately. Bright white paper! I was gleeful, but, still perplexed.

How can the ostensibly same paper vary so much from batch to batch so as to produce such differing results when all other factors of chemistry, temperature, pH, and humidity, are the same? Does paper deteriorate as a support for Pd/Pt printing over time or exposure to air, heat, and humidity? Or, is the difference in the manufacturing process that somehow varies?

Any info you may have on this topic would help me, and perhaps others, avoid similar setbacks such in the future.

(Attached are two test prints in which all exposure and processing factors are the same. The only difference is that in the lighter cleared print, the paper is from a different package.)


There is still something very strange going on with either your brush/coat or your developer or both . . . I actually don’t know if this is your paper . . . Tell you what, please ship me a few sheets of the bad batch and I’ll do a test on the chemistry that we have in our lab. I am in contact with the hahnmuhle mill for these batches so it’s helpful for them to get this info if it is the paper.





I agree with Walker - there is more going on here than just a bit of fog. I’d be a lot more concerned about the coarseness, or should I say lack of smoothness, in both examples. You don’t specify exactly what your coating mix is. You say 50%FO/50%Pd/Pt.

  1. What is the actual volume of each component? (In drops, ml, ul, etc - whatever method you use to measure.)
  2. What exactly is the composition of the Pt/Pd part?
  3. Are you using any surfactant such as Tween 20, and if so how much?
  4. How do you prepare you ferric oxalate?
  5. What is the humidity in your workspace?
  6. What is the temperature?
  7. How do you dry the coated paper?
  8. How dry do you get it?
  9. Do you rehumidify it?
  10. Do you develop at room temperature?
  11. Is the developer fresh?
  12. What is the pH of the developer?
  13. Have you tried potassium oxalate developer?
Not related to the fog or to the grittiness, but tetrasodium EDTA by itself is not a particularly effective clearing agent. The clearing baths are not expected to have any effect on gray tones, though most papers lighten slightly during clearing, the tones dry back down. Clearing baths remove residual ferric (and ferrous) oxalate which are yellow-orange in the uncleared print. Any hint of residual color after clearing is a clear visual indicator of insufficient clearing. Unfortunately, not all residuals are visible, hence the need for being meticulous about using a chemically sound clearing procedure.


This is not a problem with the paper~


Thank you for your detailed reply, Keith.

I can see now that my fogging problem is probably not a result of the paper, but in the composition and application of the sensitizing solution.

  1. For a 7" x 10" glass rod coated sheet, I use 37 drops of sensitizer; 18 FO + 15 Pd + 3 Pt + 1 PhotoFlo (1:4)
  2. Humidity: 54% Temperature: 72°F
  3. Sensitized paper is hung to mostly air dry in near darkness, with a minute or two under a hair dryer on low if I'm printing immediately.
  4. If printing the next day, I re-humidify the paper over a closed cover bath of warm water for 90 seconds.
  5. My Ammonium Citrate developer is fresh and has a pH of 4.5 which I use at room temperature. I prefer cool black tones, so I haven't tried Potassium Oxalate yet although I have just received a shipment of some from Bostick & Sullivan.
  6. After reading Pradip Malde's recommendation on this blog, I've ordered disodium EDTA but it hasn't yet arrived. So I'm still using Tetrasodium EDTA with PermaWash in baths 1 & 2; and EDTA + Sodium Metabisulfite in bath 3.
  7. Concerning mixing the 27% ferric oxalate, I had great difficulty getting a recently mixed batch to fully dissolve, so I used a magnetic stirring unit with a temperature controlled heating plate. In my zeal, I may have overcooked it, raising it's temp to 81°C (177.8°F).
I read somewhere that adding a small amount of hydrogen peroxide will convert the undesirable ferrous back to ferric oxalate and lead to less fog. It was suggested as a way to revive out-of-date FO that contained too much ferrous oxalate.

So I slowly added about 10ml of 35% hydrogen peroxide to the 100ml jar of overcooked ferric oxalate solution. (If you try this at home, wear protective glasses, rubber gloves, and an impervious apron because H2O2 at 35% is extremely caustic. It is readily available from most agronomy suppliers; it’s used to feed plant root systems.)

Attached are two new 256-step Colorport targets I printed this evening using that FO solution. The one exhibiting unevenness, grain, and fogging is the print made with FO before adding hydrogen peroxide. The 2nd print with less grain and smoother gradations is after the addition of 10ml of hydrogen peroxide to the sensitizing solution. All other factors, temp, humidity, processing chemistry, clearing, and washing were identical.

The print made with the FO + H2O2 shows no perceptible fogging whatsoever.

I look forward to hearing your thoughts as I continue to experiment with this solution.



Was this Boston and Sullivan FO from us at InkjetMall or directly from BS?

We had the same issue on a batch of FO from BS but I don’t think we packaged this for sale. We scrapped the whole batch.






Hi Mark,

I have no idea if you are new to Pt/Pd printing or an old hand at it, so forgive me if any of my comments are too obvious or obtuse - they come from over 25 years of practice. I’ll comment on each of your points in order.

  1. Drops. It turns out that drops of different substances do not necessarily have the same volume. In this case, a drop of Pd is slightly larger than a drop of FO (I'm not sure about Pt but I suspect it is the same as with Pd) leading to a slight excess of metal salt if an equal number of drops of sensitizer and metal solutions are used. This can sometimes be the cause of a certain grunginess in the highlights or in what should be clear margins. If this is the case, the solution is to reduce the number of drops of metal solution until the problem disappears. A better solution is to use pipettes of the appropriate size to measure your solutions. I have used plastic transfer pipettes for many years, but they are not very accurate either. Recently I found a source for inexpensive adjustable pipettors and have been happily using those for the last few months. Your drop count is probably roughly equal to 2ml, but since a drop is not an accurate unit of measure it's hard to be sure.
  2. Your humidity and temperature are pretty much ideal. I do want to note that I had an issue with HPR 2 summers ago that we ultimately determined was due to the unusually prolonged period of higher temperature (~80F) in my non-air-conditioned darkroom. The problem ended when the temp went back down to below 75F.
  3. Both of those drying methods are fine, but you should be consistent in practice. The amount of moisture in the paper at exposure does have an impact, and each paper has it's own sweet-spot. But ... If you are going to rehumidify in a controlled manner, that should help eliminate that as a variable.
  4. This sounds like you sometimes allow the coated paper to sit overnight before printing. My experience with this was not good. It always led to fogged highlights. Even coating several sheets at the beginning of an all-day session proved unsatisfactory since the longer the time between coating and exposure the higher the likelihood of fog. Maybe others have had better luck with this kind of routine than I have.
  5. I rarely use ammonium citrate anymore, but on the rare occasions that I have in recent years I have always notices a bit of unevenness in the mids and highs that I don't get with potassium oxalate. I think I see this in your examples too, even the better ones, assuming it's not caused by something else. I have also found AC to be a bit slower (needs more exposure) and more contrasty than PO - this can vary quite a bit among different papers.
  6. I switched fully to the Malde-Ware clearing routine last year. (I had been using a sort of variant of it for years without realizing it.) It's actually simpler than it sounds. Bath 1 is disodium EDTA, which can also be made by adding citric acid to tetrasodium EDTA. In tablespoons it's 3 tetra-EDTA plus 1 citric acid per liter of water. Disodium EDTA can be difficult to dissolve, you may need to heat the water. Bath 2 is sodium sulfite, sodium bisulfite, or sodium metabisulfite (or Kodak HCA or PermaWash). I can't deal with the smell of sodium metabisulfite, so I use sodium sulfite instead. Bath 3 is tetrasodium EDTA.
  7. It's very possible that you overcooked the FO if you kept it at that temp (~180F) for an extended period of time. The stirring is essential but not the heat. The last batch I made a few weeks ago took 3 days to dissolve completely, but it did and it's good. In Mike Ware's recently self-published Platinomicon (free download from his website), there is a small section on the classic develop-out process where he uses B&S ferric oxalate powder. He says not to heat it at all, but to expect it to take at least a day (20 hours) to dissolve. (See pp. 133-134.)
I've read somewhere about salvaging bad ferric oxalate with H2O2 too (;)), but had never tried it. Good to know it works. The big question will be whether or not you get consistent results to normally mixed FO.

If you are willing to try a little experiment, I’d be interested to see how a mix with equal amounts of Pt and Pd developed in potassium oxalate compares to this. Specifically if it is smoother than what you are getting with AC and if it is cool or neutral enough for you.

And finally, you mention that you are using 1 drop of PhotoFlo diluted 1:4. I have found that I get the best results on HPR with twice the amount of surfactant that I use on other similar papers. I normally use 1 drop of 10% Tween 20 per ml of total solution, so for an 8x10-ish print that is about 2ml + 2 drops. For HPR I would use 4 drops. I’m not sure how that translates to PhotoFlo, but I suggest you may want to try not diluting it at all, and see if that makes a difference.



The difficult to dissolve FO powder was purchased directly from Bostick & Sullivan in 50g bottles. On the label are instructions that read:

“Heat 100ml of distilled water to 180°F. Add 25g of Ferric Oxalate powder to hot water.Sir quickly for 30 seconds. Solution should dissolve complete within 10 minutes.”

Admittedly, I have not been making FO solution for very long, but I’ve never had it dissolve in anything less than 24 hours. It’s more like 48 to 72 hours with multiple re-warmings. Since then, I’ve watched a couple of YouTube videos demonstrating the heating process using a bain-Marie to raise the solution temperature slowly to no more than 140°F. I’ll give that a try on my next batch.


Thanks, Kieth.
You’ve made several good points in your reply. I am very grateful for your suggestions because I comparatively am new to Pd/Pt printing. My first exposure (pun intended) was at the Cone PiezoDn workshop in the fall of 2016. Since then, I’ve built a darkroom modelled on Jon Cone’s method. My first 50 prints exhibited excellent range in shadow detail and highlights, but, then I took a break from printing. When I returned to it a couple of months later, I started to see the degraded highlights, loss of shadow detail, and increased graininess. An existential crisis ensued.

Most likely, my print problems are not attributable to just one factor, but, are the result of several variables going slightly awry from my initial good luck. I will continue to refine my process until I obtain consistent and predictable results.

I am particularly intrigued by your perspective on drops. I’ve long suspected not all drops are created equal; it’s easy to see that a drop of Palladium solution is fatter than a drop of FO. Eye droppers of differing lengths and diameters seem to produce differing size drops, too. I will take your suggestion and invest in accurate pipettes. Also, at your suggestion, I’m going to try PO as my developer in my next printing session. I will report back on the results.



If your “FO” is not completely dissolved, how do you determine it is 27%


Ting - If I don’t get the FO to dissolve completely I don’t use it. There probably is a way to determine the concentration of incompletely dissolved FO solution, but it’s beyond my knowledge. Maybe specific gravity or something.


You can use “hydrometer”。25% FO=>1.16 27% FO=>1.17 30% FO =>1.19

But “B&S iron oxalate”, may have EDTA, so I can not confirm.

I made “FO” by myself.


Ah yes. My memory isn’t quite as bad as I thought. I’m fairly certain there is no EDTA in B&S ferric oxalate powder or liquid. Some printers (me, for instance) add a small amount.

Why are you putting those terms in quotes? They don’t need to be in quotes unless you are trying to imply that they are not what they claim to be.

What formula do you use? I’ve come across a few.


This is nonsense like so much else coming from B&S recently, such as advocating single clearing bath, and using a ridiculously high level of restrainer as a standard formula for Pt/Pd and digital negs.

Even in the old days when they were in LA before moving to Santa Fe, when 120F was hot enough to dissolve the FO, it always took at least a few hours. Sometime after they moved to Santa Fe I started noticing that it was taking longer and longer to dissolve, and notified them of this several times, as I’m sure others did too, before they finally started recommending higher water temp, 150, 160, then 180.

Overnight with constant stirring is normal now. Start with the water at 180 (or boil in the microwave), but don’t try to keep it that hot.

Also, don’t expect the powder to have a shelf life of more than 2 years. You may get lucky, but more likely not.
I think all of this is related to Mike Ware’s characterization of ferric oxalate as an “ill-defined” substance.

And besides that, the method quoted results in a solution that is less than 25%. (The stated 25gm is because they too have difficulty getting 27gm to dissolve fully in 100ml.) The correct method is to start with about 80ml of hot water, add the powder(s), stir until fully dissolved, then add more water to make 100ml.


Try to add some potassium ferricyanide solution to the iron oxalate solution before coating to test the iron content inside.

A few years ago, when I tried B&S iron oxalate, there was never an iron reaction.

Sorry, Just poor English.



I’m familiar with that test - it’s not very reliable, but can be useful if you know it’s limitations and how to interpret it.

This is from an old article by Phil Davis:

There's a well-known test that will reveal the presence of ferrous oxalate in the sensitizer: simply add a drop of weak potassium ferricyanide solution to a few drops of the sensitizer solution. No color change, or a very slight one, indicate that the solution is essentially ferrous-free; a pronounced blue color will result if there is ferrous oxalate present.

Although this is an interesting and enlightening chemical test it’s almost too sensitive to be
practical. I certainly don’t want to encourage you to be careless or sloppy but you should be
aware that a trace of ferrous oxalate in the sensitizer (certainly more than enough to fail the
ferricyanide test) is not going to have any visible effect on your prints. If you discard your
solutions as soon as they react visibly with the ferricyanide you’re wasting money.

As a rule of thumb, ferric oxalate solutions are probably usable (but not necessarily in first class
condition) as long as they remain completely clear and free from any trace of precipitation. But
don’t interpret this as license to use sensitizers that are truly spoiled. Any suggestion of
cloudiness or sediment is cause for real concern.

Ferrous oxalate is certainly a serious contaminant but its gradual build-up in the sensitizer
solution worries me less than its much more obvious presence as a dry sage-green crust that’s
very likely to form around the mouth of the sensitizer storage bottle and on the inside of the
dropper cap. Flakes of this material that may fall back into the solution, or onto your freshlysensitized
paper, are genuinely worth worrying about. So are traces of ferrous oxalate that will
surely contaminate your coating brush if you don’t wash it immediately and thoroughly after
each coating operation.





How to determine that there is no “EDTA” in “B&S Iron oxalate”




I found two recipes for the addition of the hydrogen peroxide to ferrous oxalate to convert it to ferric oxalate in the context of the Kallitype printing process. However, the solution seems to be suitable to FO for Pd/Pt printing as well.

The first is from the Book of Alternative Photographic Processes by Christopher James:


The second is Coming Into Focus: A Step-by-Step Guide to Alternative Photographic Printing edited by John Barnier