Problem with the Ferric Oxalate solution for Pt/Pd.

Dan Pavel · Dec 1, 2020

Due to the pandemic my provider of chemicals for Pt/Pd, DISACTIS PHOTOCHIMIE, temporary doesn't ship to my location. I still have some Ferric Oxalate powder and I tried to make the solution myself, but without success. I tried 3 times with the same result (Bergger COT 320 paper).

I've tried progressively to add some Oxalic Acid to the solution but the result remained the same. I still have some 30ml of 1 year old Ferric Oxalate solution and it proved to be much better than the new one.

However, the black zones are not as black as they should be and I wouldn't trust it for new prints (...or should I trust it? What's your advice?)
Is there a way to make the new Ferric Oxalate solution work properly? I should mention that my Ferric Oxalate powder has a yellow-brown color.

DMJ · Dec 1, 2020

I cannot give you much advice but to test Ferric Oxalate Bostick recommends a fog test:

https://www.bostick-sullivan.com/articles/ferriccoalate.html

Others recommend to add a 5 percent solution of potassium ferricyanide to a ferric oxalate solution dissolved in water. If the mixture turns blue, the ferric oxalate has become ferrous and will deliver poor results. (This method is not recommended by Bostick)

Martin

Alan9940 · Dec 1, 2020

I don't ever trust my FO beyond 6 months. After that, I'll toss it and mix new using 6.2g to 25ml warm water in a brown glass bottle. I put the powder in a dry bottle, pour in the warm water, and shake it vigorously for a bit. Then, I toss it in my pocket and go about my normal life shaking it every so often. Let it sit overnight, give it a couple of shakes in the morning and you should be good to go.

Dan Pavel · Dec 1, 2020

Thanks Martin. i don't have any Potassium Ferricyanide for the moment but I suppose that the amount of Ferrous Oxalate is the real problem with my solution and I don't know how to reduce it (if possible).

Alan9940 said:
I don't ever trust my FO beyond 6 months. After that, I'll toss it and mix new using 6.2g to 25ml warm water in a brown glass bottle. I put the powder in a dry bottle, pour in the warm water, and shake it vigorously for a bit. Then, I toss it in my pocket and go about my normal life shaking it every so often. Let it sit overnight, give it a couple of shakes in the morning and you should be good to go.

The method I've used is quite similar with the exception that I added 0.5g of Oxalic Acid in the solution from the beginning. For agitation I use a small electric motor with very low speed and let the bottle get shaken all night. In the morning I filter the solution and let it rest till in the evening, when I test it.

nmp · Dec 1, 2020

Hi, Dan:

You could try using some hydrogen peroxide per Dick Sullivan:

https://www.bostick-sullivan.com/articles/fo_carefeed.html

:Niranjan.

Dan Pavel · Dec 2, 2020

Thanks Niranjan. I'll try it.

Dan Pavel · Dec 2, 2020

Thanks again Niranjan. Adding 7 ml of Hydrogen Peroxide to 30 ml of solution really solved the problem!
I increased the exposure time from 3 min. to 5 min. and now the test print looks as it should, with clear whites and deep blacks (deeper than they appear in the scan). From now on I'll make adding Hydrogen Peroxide to the Ferric Oxalate solution a standard procedure.

nmp · Dec 2, 2020

Dan Pavel said:
Thanks again Niranjan. Adding 7 ml of Hydrogen Peroxide to 30 ml of solution really solved the problem!
I increased the exposure time from 3 min. to 5 min. and now the test print looks as it should, with clear whites and deep blacks (deeper than they appear in the scan). From now on I'll make adding Hydrogen Peroxide to the Ferric Oxalate solution a standard procedure.

View attachment 260832

I am glad...though I am not sure this is a good preventive measure in the bottle since peroxide will deplete on its own over time. It will also create some pressure depending on the amount. So be careful.

Was this the solution you just made with the powder - if that's the case I am surprised it was compromised. I thought the powder lasted years. What if you use a drop or two only to the FO that you are using to make the print (before adding the metal.)

:Niranjan.

Dan Pavel · Dec 3, 2020

Yes, it was made it starting with powder. Probably the powder conteins a grater than optimal amount of Ferrous Oxalate.
Dick Sullivan says:
"Add hydrogen peroxide to it. This will clear up any slight content of ferrous oxalate to ferric oxalate, and will act as a long term preservative. Some outgassing may occur with the use of peroxide, and vented cone caps should be used so the bottles do not explode."
I usually change the solution every 4-6 months and I don't think that the peroxide, being a preserver, will deplete the solution sooner than that. I intend to dilute the oxalate in 20 ml of hot water and after 1 day to add 5 ml of peroxide to it and continue the dilution until it clears. Practically I'll replace 5 ml of water with peroxide in the final solution. Anti-pressure measures will only be needed in the first day after making the solution. After that no notable pressure appears.
I don't think that adding the Peroxide to the FO before making the print is safe enough before it takes some time for the peroxide to do it's job.
Anyway, I'll test it and see how it behaves in time.

nmp · Dec 3, 2020

Dan Pavel said:
Yes, it was made it starting with powder. Probably the powder conteins a grater than optimal amount of Ferrous Oxalate.
Dick Sullivan says:
"Add hydrogen peroxide to it. This will clear up any slight content of ferrous oxalate to ferric oxalate, and will act as a long term preservative. Some outgassing may occur with the use of peroxide, and vented cone caps should be used so the bottles do not explode."
I usually change the solution every 4-6 months and I don't think that the peroxide, being a preserver, will deplete the solution sooner than that. I intend to dilute the oxalate in 20 ml of hot water and after 1 day to add 5 ml of peroxide to it and continue the dilution until it clears. Practically I'll replace 5 ml of water with peroxide in the final solution. Anti-pressure measures will only be needed in the first day after making the solution. After that no notable pressure appears.
I don't think that adding the Peroxide to the FO before making the print is safe enough before it takes some time for the peroxide to do it's job.
Anyway, I'll test it and see how it behaves in time.

It all makes sense.

Once I tried to add peroxide to cyanotype sensitizer thinking it will help to reduce blue staining in the unexposed areas. It did the opposite for some reason and I didn't follow up to figure out why. Perhaps something to do with the pH - as it can act both as an oxidizing agent and a reducing agent depending on the conditions.

:Niranjan.

Problem with the Ferric Oxalate solution for Pt/Pd.

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