Ferric oxalate issue

Dear All,

We are encountering problems in the making of ferric oxalate.

Until now we have used ferric oxalate from a small lab with very good results, which was fabricated from a standard recipe. However we are working on a larger project and need more ferric oxalate than they can produce on a regular base.

Subsequently we purchased ferric oxalate crystals from ProChem in Rockford, IL. We solved 27g crystals in 100ml distilled water in a glass beaker. We where using a magnetic stirrer with a hot plate at 100degF and stirred it for 30 min. The color was a clear amber yellow. The solution was filtered with no trace of residuals. No metal was in contact with the solution.

We coated the Revere paper with a mixture of Pt/Pd and ferric oxalate (1:2:3), developed it in potassium oxalate and cleared it in citric acid and EDTA, just as we normally do.

The result was devastating. The whole surface of the coated area was covered with a gray fog.

Now we are trying again with the Bostick & Sullivan ferric oxalate crystal set, which we purchased trough Inkjet Mall.

Before we will try again, could anybody give us advice what potentially went wrong and what would be the best practice to solve the B&S crystals?


Christoph Heidelberger

PtPd-scan.pdf (172 KB)

PtPd-scan-1.pdf (172 KB)

That gray fog means that your ferric oxalate is actually ferrous oxalate. In 25 years of Pt/Pd printing, I’ve never come across ferric oxalate sold in crystal form. I would be suspicious of that. B&S ferric oxalate is (and has always been) a very fine yellow-green powder. Add 25gm to 100ml of distilled water at 180°F. It didn’t used to require mixing at such a high temperature, but it has for the last several (10 or so) years. It may take up to 24 hours to dissolve completely. If you don’t believe me about this, call B&S!

I know of a few people who make their own ferric oxalate, but it’s not something for those without fairly good chemistry lab skills.

InkjetMall only sells the Bostick & Sullivan Ferric Oxalate powder. So Christoph, you have ferric oxalate from us - not ferrous oxalate. Give it a go!

Here is an excellent description of the chemical reaction that takes place in Pt/Pd printing:


Dear Jon and Keith,

In the meantime the B&S ferric oxalate has arrived. I am glad to report that it was tested successfully. As proposed by Keith we mixed the ferric oxalate with demineralized water at 180degF, while is was cooling down we stirred it with a magnetic stirrer for 24hrs, filtered it and added the oxalic acid. The result is perfect. Even unexposed areas under the red light mask cleared perfectly. Thats where we had problems with B&S oxalate about 10 years ago which led to making our own oxalate.

Thank you very much for the advice and the article about the oxalate/PT/Pd chemistry. Very helpful indeed.

With kind regards,

Christoph and Ursula