Witish veil on pd prints
I have a problem on my pd prints. It's going to be a bit long as I'll try to describe te process in a comprehensible english :-)
The pure palladium prints are covered with a witish veil. Surprinsingly, this veil is much stronger always in the same corner of the print, at the upper right. The paper is Crane's cover. I used the same paper batch for one year and have first encountered the problem at the fall of autumn. I thought it could be a cold snap variant and tried to solve it. It disappeared (I don't know exactly why), and I met it again some days ago. Here are the complete very common process and materials used. I tried of course to isolate the variables, but I don't understand.
- Darkroom is about 21-23 degrees C.
- Humidity is 55-60 %, now controlled with an ultra-sonic humidifier in the room. I had no u-s humidifier the first time the problem happened and humidified the paper in a humidifying box before coating.
- Paper is Crane's cover, single-coated wit rod. I have not the problem with other papers, Simili Japon or COT. The paper is stored at least 12 hours before printing in the darkroom. Sometimes I give some more slow additional humidification after coating with a humiification chamber or a faster one over the u-s humidifier. I sometimes use Crane's paper stored in an another room with lower humidity, humidifying slowly the paper just before coating. Nothing changed.
- I use fresh FO, or 8 days old max.
- Pd is home made PdCl. Chemicals from Artcraft, 15+15 drops for a 8x10 negative.
- Developer is potassium oxalate at 40 degrees C. I thought the problem could occur because when using it hot, the developer could oxydize more quickly, and that it would be better to discard it frequently. As I use it hot, I shortened the time in developer. I tried 30 and 45 seconds, 1 minutes and 2 minutes. No changes : veil.
- There is one corner always more withish than other. I understood it was the corner that was directly under tap water when I washed the print after developing (of course the paper is not directly under water, water flows in the tray, always in the same corner) . But here I always forget to watch the temperature of the washing : could it be the problem ? Does one with hot PO use cold or rather hot water for washing after developing ?
- As I used HCA for clearing, I thought it could be the problem with pure pd. Usually 1 citric acid bath + 2 HCA baths, 5' each with washing between baths. I tried 3 acid citric baths and EDTA baths : no change, it veils.
- Final wash is 30 mn max in a vertical washer.
I see 4 possibilities :
1/ Paper. But I printed many times with it without problem.
2/ Hot developer. I changed once and met again the problem.
3/ Washing just after developing.
I guess the answer is 2 or 3. Maybe the solution is very simple, but what makes me crazy is that I don't always meet the problem, and I can't isolate the problem. I would be happy to read your comments and suggestions.
Whitish, of course, not witish :-)
If you are using a printing frame try rotating 90 degrees half way thru exposure to make sure it's not your exposure unit as one corner is always whiter. Try clearing with edta and sodium sulfite, one teaspoon each to one quart water. Possibly citric acid is bleaching print. I use warm water rinse after dev. before first clearing bath and between clearing baths. After coating paper how long do you let it rest before drying? You might try changing this variable. Do you pour dev. over print or slide print into tray of dev.? If dev. is not reaching all of print quickly it can cause a surge line maybe in that same corner so it would be lighter. Would be worse with hot dev. Just a few thoughts. Good luck and hope you get this figured out soon as these type of problems are frustrating.
Thank you for your help. I tried EDTA and sodium sulfite. About drying, I let the paper air drying about two minutes (formerly 5 mn), and then dry it with a hair drying. I usually print quickly after coating. I pour quickly the dev on the print in the tray, nothing wrong here.
Thinking to my original post and searching in my notes, I remember I had briefly the same problem one year and half ago with COT 320. I solved the problem using new developer.
My recent problem disappeared and came back using the same developer. Another idea I thought after writing : with this developer, I made some trials raising the pH. The original formula is 130 g oxalic acid and 110 g potassium carbonate per liter. Adding chemicals to modify the pH could be the cause : the formula is very stable with the original components (about 4-4.5) but becomes very unstable when playing with carbonate and acid to raise the pH. Maybe the solution is here. But I don't understand why one day I have the problem, the other not with the same developer.
Originally Posted by Jimmy Peguet
You should not raise the pH of the developer. In fact, if anything add an excess of oxalic acid to make sure it stays very acidic. The primary cause of staining in my own work, both in kallitype and with pure palladium, is conversion of residual ferric salts to iron hydroxide in an alkaline environment. If you keep your developer acidic and make sure that the water of your first wash is also on the acidic side, you may solve your problem. It might also be helpful to add a small amount, say about 2% by weight, of oxalic acid to your ferric oxalate.
Also, I use the dichromate contrast control method with pure palladium and I get much better clearing with this method than with Na2 and other methods.
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I have found this problem a few times and this is what I concluded. The first time it was the negative, I have this one negative that looks great, when the print is wet it looks great, but once it dries I get the veil you mention.
If you are doing pure pd, try doing a double coat. I have seen the veil when I did not use enough solution, this could be solarization. With the rod and the magic brush we tend to try and use too little. I have found there is an optimum amount, any less and you get solarization, and of course, more is a waste.
Try and expose your print within one hour of coating. Let it dry, do an extra 5 min with a hair drier and then expose.
HCA should not be the problem, all clearing baths solubilize iron salts and should not have an effect on metal pd, with the exception of Hydrochloric acid, which can oxidize pd if used too strong.
This is how I have avoided the "veil", hope it works for you.
I've always worked with an acidic developer, except for some trials. The first time I met the problem was with an unmodified developer). It's far more easy to clear, and I always add a bit of oxalic acid in the FO when mixing. I checked the pH of the developer : it's now stabilized at 4.7. Maybe the problem is that for these trials, to stabilize it, I added acid, then carbonate, then acid... maybe too much chemicals. At the beginning, the formula always stays around a pH of 4. When trying to raise it to about 6.5, it stays at 6.5 during the print session, but some days after it raises to 8 or 9. Then I add acid, and so on. It doesn't explain why one day prints are good, the other not with the same PO, and why white in the same corner (problem of light, as William suggested ?). I think the best is to discard the developer and to see if it happens again with a new one.
In case of use of hot PO (40°C or 104°F), do you have to discard it frequently, or is it always OK ?
Jorge, it's exactly like what you describe (something like a very thin coat of white sodium sulfite on the print when dry, not visible when wet). I'll try with more drops. But I don't see any solarization here, blacks are really good, and I think there are enough drops for a 8x10", and I never had until now the need for double coating on Crane's.
Thank you all for your answers.
Is it possible one corner is getting more exposure and you are getting some solarization (density reversal with overexposure) I have noticed this problem on the black border areas of single coated prints on a variety of papers. Solutions are to make sure the paper is humidified properly and possibly double coat the papers that can take the two coats of sensitizer. The fact that it is confined to one corner makes me think it almost has to be something to do with the exposure - you would think that any paper or chemistry paper would affect the whole print.... I dunno, good luck!