Troubles with thiourea and gold toning
After reading Tim Rudman's book on toning, I have been experimenting with
thiourea and gold toning, and I have encountered some problems. I would
like to ask for counsel here in order to solve them, if possible.
The pictures below show perfectly the problems.
They were copied the same day, on Ilford MGWarmtone, developed with Ilford Warmtone developer, 1+9,
odourless stop bath, tetenal superfix 1+3 1m, rinsed during 5m, lavaquick during 5m and washed
during 30m in a washing processor. They may have slightly different grades and exposures.
The toning session was some days later. Each copy received a different treatment:
1. KRST + gold,
2. KRST + thiourea + gold,
3. KRST + thiourea,
The process was the following (some of the steps have been skipped if the corresponding
toner wasn't performed):
soaking in water, KRST, short wash, lavaquick, long wash, bleaching (ferri + potassium bromide,
1+29, different times), short wash to get rid of yellow stain, thiourea, long wash, gold, fixer, short wash, lavaquick, long wash.
My main concern is with picture number 2. You can see that the clouds in the sky are full of
irregularly distributed pink stains. These stains appeared during the gold toning after the thiourea.
I don't know were they came from. They do not appear if the thiourea is skipped (picture 1) or if
the gold is skipped (pictures 3 and 4) independently of the selenium step. I have two different guesses:
- not enough wash after the bleach (but, then, why that pattern?)
- the water is very hard (here in Barcelona), and when the print was left to dry, the drops
dried and made some invisible stain in the copy which, with the thiourea - which is a quite strong alcali,
with the hydroxide - and the gold, become visible.
In my next session I was going to perform a final rinse in deionized water after the wash, in the printing stage
and a deeper wash after the bleach. However, if someone has some ideas on the subject, please, enlighten me!
The second concern is visible in picture number 4. There are some deposits on the surface of the copy.
I think they are calcium deposits form the hard water wash after the thiourea step (which has a very high ph).
I was thinking about including an acid stop bath step between the thiourea and the wash in order to lower pH, but I could use some advice
I have included picture 1, where everything looks ok, for reference. Picture 3 has also some stains, similar to
those in picture 4.
Please forgive the long post. I will appreciate any advice.