clearing Pd prints in situations with alkaline tap water

jscottyk · Jan 8, 2017

I’ve been tracking down the source of density in the highlights of recent calibrations and after ruling out chemical fog, finding a bit of UV induced density, I found that the culprit is my very alkaline tap water. As in pH 9.6 (reported; I’ll test very soon).

During some test last night and reading here APUG and largeformatphotography.info I suspected my tap water could be driving this. On a whim I tossed some vinegar in the first clearing bath. Viola. It didn’t completely clear I suspect because the stain was set in during a two minute wash of warm tap water after development.

My emulsion is Pd with a drop (or two) of Na2, developer is potassium oxalate. Paper is Hahnemuhle Platinum Rag. Clearing baths are mix EDTA and a Permawash.

I am certain this is a main driver of the stain (not fog) but am not 100% of the workflow to solve it.

Has anybody else solved this problem? Or have thoughts?

Bob Carnie · Jan 8, 2017

I will be curious to see how this goes, I started using Citric Acid as the first clearing bath and It seemed to work better for me.

Vaughn · Jan 8, 2017

Our water is fairly neutral, but I still use a citric acid first clearing bath. Occasionally I'll rinse a print off before hitting the first clearing bath...so far no noticible difference.

jscottyk · Jan 8, 2017

With very alkaline tap water, I have read that wash (which I have done) could be part of the problem. I going to test skipping that and instead using the citric acid bath before the clearing baths.

dpurdy · Jan 9, 2017

The best clearing bath is still the original way of doing, it is hydrochloric acid. Cheap at a chemical supply house and every city has chemical supply houses. Somewhere along the line, on the on line forums, people started saying hydrochloric acid was too dangerous and everybody started using EDTA or Citric Acid or Hypo Clear or what ever. The best has always been hydrochloric acid. Clears your prints the best and quickest and cheapest. You get the 27% strength and dilute it 20ml to a gallon of water and use three baths with agitation.

Ian Leake · Jan 9, 2017

Yes, in my experience clearing with dilute acid is best. I use three baths of 0.75%-1.5% citric acid depending on the paper.

pschwart · Jan 9, 2017

HCl is effective, but not necessarily the "best."
There is a good reason why many platinum printers don't use hydrochloric acid: it's damaging to paper. Citric acid, EDTA, and sulfites (hypo clear) are safer, effective, and much gentler to paper than HCl.

Vaughn · Jan 9, 2017

pschwart said:
... it's damaging to paper. Citric acid, EDTA, and sulfites (hypo clear) are safer, effective, and much gentler to paper than HCl.

Is the damage caused to paper because HCl is used too strong, or just a function of the type of acid?

pschwart · Jan 10, 2017

That's a fair question and I don't know the answer. I recall Mike Ware recommending Na2EDTA, Na4EDTA, and sulfite/bisulfite (hypo clear) over HCl, but don't recall if he did any testing of HCl.

Vaughn said:
Is the damage caused to paper because HCl is used too strong, or just a function of the type of acid?

Martin Rickards · Jan 10, 2017

When I was working in chemistry we used to filter stonger acids through paper with no adverse reactions. This included molar (about 3.5%) hydrochloric acid. You seem to use it much more diluted than that (0.1%?).

pschwart · Jan 10, 2017

The question is: how does the HCl affect the paper structure OVER TIME.

Martin Rickards said:
When I was working in chemistry we used to filter stonger acids through paper with no adverse reactions. This included molar (about 3.5%) hydrochloric acid. You seem to use it much more diluted than that (0.1%?).

dpurdy · Jan 10, 2017

pschwart said:
The question is: how does the HCl affect the paper structure OVER TIME.

Well I am old, in my 60s and I started printing platinum in my 30s. I have always used hydrochloric acid and if the paper is damaged you wouldn't know it by me.
Also there is lots of evidence that platinum prints last a really long time and until relatively recently everyone used hydrochloric acid as far as I know.
There is also this impression people have that a platinum print develops instantly upon contact with developer. I have learned that my prints clear much more quickly if I let the print sit in the developer at least a minute and I usually leave it more than 2 minutes. Since i have started that, a few years ago, my prints clear quickly and cleanly.
Dennis

pschwart · Jan 10, 2017

dpurdy said:
Well I am old, in my 60s and I started printing platinum in my 30s. I have always used hydrochloric acid and if the paper is damaged you wouldn't know it by me.
Also there is lots of evidence that platinum prints last a really long time and until relatively recently everyone used hydrochloric acid as far as I know.
There is also this impression people have that a platinum print develops instantly upon contact with developer. I have learned that my prints clear much more quickly if I let the print sit in the developer at least a minute and I usually leave it more than 2 minutes. Since i have started that, a few years ago, my prints clear quickly and cleanly.
Dennis

Absent specific criteria and testing, I am inclined to question claims that a particular working method is "best." If you are satisfied with yours, certainly no need to change. The point is there are alternatives. The chemicals I stock for pt/pd get used for other processes, which is another benefit for me.

Michael Mutmansky · Jan 16, 2017

HCl is not the best clearing agent, but it probably is the strongest. However, it can cause bleaching of the pt/pd and I have seen it cause bleaching in the paper fibers as well with natural paper. It is also a source of corrosion of anything metal in the darkroom, and is volatile so it should be used with a proper breathing mask so it does not damage the cilia of your lungs, plus your eyes...

Basically, don't use the stuff. There are much better ways to clear paper (with fewer problems), and if you can't clear the paper with a less aggressive choice, you may want to find a different paper.

Some people acidify the paper before coating because it improves the dmax, and it will also keep the paper a bit more acid until you are in the clearing baths.

I make a point when I mix my potassium oxalate to mix it so that it is on the acid side of balanced. That is, I mix the oxalic acid and the potassium hydroxide until they are consumed, and then add a bit extra oxalic to the solution. Use this just like normal, but since it is the first solution that gets into the paper fibers, it makes the paper slightly acid which helps with the clearing.

You can also dispense with the water bath after the developer and go directly to the first clear bath. If you are using EDTA, you are probably going into an acid solution and you shouldn't have too much problem avoiding having the stain set in the paper.

Philip mentioned above citric acid. That is my primary clearing agent. I sometimes follow up with some EDTA as well.

---Michael

dpurdy · Jan 16, 2017

Michael Mutmansky said:
HCl is not the best clearing agent, but it probably is the strongest. However, it can cause bleaching of the pt/pd and I have seen it cause bleaching in the paper fibers as well with natural paper. It is also a source of corrosion of anything metal in the darkroom, and is volatile so it should be used with a proper breathing mask so it does not damage the cilia of your lungs, plus your eyes...

Basically, don't use the stuff. There are much better ways to clear paper (with fewer problems), and if you can't clear the paper with a less aggressive choice, you may want to find a different paper.
---Michael

I suppose if you are a very careless worker you can give yourself trouble using Hydrochloric acid but it is very easy to work with and not bleach anything and not breath the fumes right out of the bottle. It is used so dilute that you will never have a breathing problem. But go ahead and be afraid of it if you want. I will continue to use it because it is the best, the cheapest and the easiest. My paper doesn't get bleached and my palladium or platinum don't get bleached because I don't walk off and leave a print in the clearing bath for an hour. My prints from 1985 are still beautiful.
Dennis

Andrew O'Neill · Jan 16, 2017

I too was having problems years ago when clearing Kallitypes, for the same reason. Citric acid in the first rinse took care of that issue.

Michael Mutmansky · Jan 17, 2017

dpurdy said:
I suppose if you are a very careless worker you can give yourself trouble using Hydrochloric acid but it is very easy to work with and not bleach anything and not breath the fumes right out of the bottle. It is used so dilute that you will never have a breathing problem. But go ahead and be afraid of it if you want. I will continue to use it because it is the best, the cheapest and the easiest. My paper doesn't get bleached and my palladium or platinum don't get bleached because I don't walk off and leave a print in the clearing bath for an hour. My prints from 1985 are still beautiful.
Dennis

Don't be daft... I nor anyone else said they were afraid of HCl. My point is that there are BETTER solutions that don't have any of the drawbacks. I regularly use chemicals of more concern than HCl, but only with proper protection, and I never use a full open tray of these things, which you clearly do.

You may never end up with problems, but I won't even consider it since there are other solutions that work as well, don't have the bleaching concerns, and have no real toxicity concerns. Like citric acid, for example.

You can use it at your choice, but I think it is irresponsible to suggest using it without also presenting the risks.

Martin Rickards · Jan 17, 2017

At the dilutions at which hydrocloric acid is used, there is no danger. Your gastric juices are probably more concentrated hydrocloric acid. You then go on merrily describing using oxalic acid as if this entailed no risk.

clearing Pd prints in situations with alkaline tap water

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