Sergio Devecchi, a member of the Namias group in Italy, has worked with alternative printing processes since the 80s. Sergio finds mysterious yellow stains on his prints. He investigates the problem thoroughly, experiments and comes up with a solution.
Some days ago I removed a photo print from the frame, both the glass and the Passepartout are acid-free material from the 90s and surprisingly it was stained in yellow both on the print and borders. It was more evident in the sun rays or with the help of a UV lamp or led lamp 14 w (100 w) cold light 6500 Kelvin – for those who do platinum and palladium printing I would suggest this simple way of checking the print.
In the 90s the treatment of Clearing was using Acid Hydrochloric and the paper was one of the earliest Arches Platine type. To investigate this issue, I started checking all the later prints I had made with other papers (Begger Cot 320) These papers had been kept in ordinary card boxes or envelopes. Even these prints revealed the same problems, despite the different procedures of clearing used at the time. Once they were printed and dry, I checked them with a UV lamp they appeared to be completely free of any ferric oxalate traces.
Later on in my printing practice, new methods of clearing were known and applied: Hypo Clearing, Edta Disodium + Hypo Clearing + Edta tetrasodium had been applied strictly but maybe something went wrong. This process dates back to ancient times but is just recently applied because of the high cost. It would not have been enough tested only comparing my earlier problems to the problems that happened in the later years A good example are the prints of famous authors kept in many museums show serious signs of decay, creating large problems for restorers and even more recent, of about 20 years, prints have these issues.
As for my work. I have always developed using Potassium O. with a 6,6 6,7 ph, not lower than that as it can compress the tonal value range and this process was supposed to be everlasting. When it started to turn yellow I used to employ a fresh product.
That is why recently I retreated these prints with Acid Citric 25 gr. /l for 10 minutes – rinsing 2 minutes – then Edta Disodium 5% for 15 minutes – rinsing 2 minutes – Hypo Clearing (Sodium Sulphite 20 gr. /l) for 15 minutes – rinsing again for 2 minutes – Edta Tetrasodium 30 gr. /L + 25 gr. Sodium Sulphite for 15 minutes- final washing for 45 minutes. This meant longer times (previously it was 10 minutes for each developing bath. Finally, I managed to eliminate 80% of the stains. Not fully satisfied I treated again one of these cleared prints using a Sodium Hypochlorite solution of 40 cc /l (for home use) at 4/5%. The result was very good but after 1 hour of rinsing the paper was still stinking too much. To make it more neutral I had to get another 2,5% Sodium Metabisulphite solution for 5 minutes, then I went on with another long rinsing session. Too much work and furthermore as the Hypochlorite is a simple optical bleaching procedure without reducing really the stains I came up with a new crazy idea. Try with Sodium Percarbonate.
“Too much work and furthermore as the Hypochlorite is a simple optical bleaching procedure without reducing really the stains I came up with a new crazy idea. Try with Sodium Percarbonate.”
Sodium Percarbonate product is not toxic, it works quickly as a whitening product as it releases active oxygen, having an as alkaline Ph as EDTA tetrasodium and, it is quite cheap. I am not an expert in chemistry but I guess that its high Ph could help even the elimination of residue Ferric Oxalate. So I prepared a solution of demineralized water 35° C with 2 litres of sodium Percarbonate 55 gr. I used this solution at a temperature of 25°, stirring in a continuous way for the first 2 minutes, then 10 seconds every 2 minutes for 15 or 20 minutes, depending on the intensity of the stain. During this stirring procedure, the solution would turn out a bit milky for the colour, with a light fizziness due to the active oxygen. I then washed it for 45 minutes.
The result
It is true that after this enforced treatment the paper becomes a little swollen but being 100% cotton and of high grammage (300 grams/m2), once it has dried again it will be as white as it was originally.
This personal contribution is not based on scientific knowledge, which I do not possess, but on a simple attempt quite empirical on how to solve this matter; surfing the web in forums or blogs I never found specific advice for this – or I just missed something. I am sharing it with you.
Footnotes
1. The printing papers are 100% cotton The sodium perborate is not recommended with linen material so they should not be used with papers 100 % linen.
2. IMPORTANT! It is necessary to go through the treatment as described earlier, starting with Acic Citric. Placing the paper straight into the sodium Percarbonate solution and omitting the previous passages will give a result not really effective. Obviously, the procedure is quite laborious and requires time but being an attempt to process a platinum print it is worth it.
In mi case it is not a conservation problem but a Clearing treatment. For about 30 year’s I have tried different types of papers and not all respond effectively to the various Clearing treatments. The Berger Cot 320 responds ” quite well” to the HypoClearing bath and is the one that gave the least problems compared to the Arches Platine of the early years but I believe that the treatment I suggested starting from Citric Acid an final bath with Edtatetrasodium as suggested by Mike Ware is most effective with most paper as the first treatment after development. Let’s hope that the passing of the years proves us right before moving on the Sodium Percarbonate…. Bye
Mr. Devecchi seems to have found an adequate solution to his problem. But it doesn’t explain why they exhibit stains in the first place. Is it possible that the Cot 320 prints show stains because they weren’t stored correctly while the Platine prints were insufficiently cleared?