Here's Kodak FD-72
Part - A
Sodium Dithionite: 5.0 grams
Part - B
Water: 900 ml
'Kodalk' Balanced Alkali or sodium metaborate tetrahydrate: 10.0 grams
EASTMAN L-(+)Cysteine Hydrochloride: 0.3 gram
Add water to make 1 litre
Use: Dissolve 5 grams of Part A in 1 litre of Part B just before use - it only has a life of about 2 hours after mixing.
Re-exposure and re-development certainly work. The problem I had when I tried it was that I went overboard -- I actually 'solarized' the film. With greater control I'm sure it would work well. I just went with the thiocarbamide method to avoid the solarisation, and I find the tone very pleasing with Pan F Plus.
Helen's formula is interesting. Cysteine was probably used because it is an inexpensive thiol source. Thiobarbituric acid is probably not controlled and is probably just like thiourea. I bet that a trace of thiourea would work just as well. Note that the concentrations are low in these formulae.
This was a sad day for me. I made a mistake.
When I tested Super Iron Out I did not re-read the fine print. It contains sodium bisulfite in addition to the sodium dithionate. It's a wonder it blackened exposed film. I thought I remembered that it had sodium carbonate. Nope.
I did another Q&D experiment, adding 1 tsp Super Iron Out and 15 ml of a 50% NaOH (by weight) solution I had on hand to 250 ml water. It blackened a piece of unexposed HP5+ in about 2 minutes in the dark.
I suspect that a solution of Iron Out alone would keep pretty well.
The 50% solution by weight is 100 grams of NaOH in 100 ml water. It's handy to have on hand. If nothing else, you can use it to clear clogged drains.
If you get the idea to use ready-mixed drain cleaner in place of the NaOH, be sure it does not contain a hypochlorite. That stuff will dissolve the emulsion. I found that out one day as a result of my other mistake.
I'll definitely be trying Patrick's method as soon as I have the chance. Thanks for that.
It looks like 10 g/l iron (II) sulphate 7-hydrate with 15 g/l potassium fluoride can be used as a fogging agent. Instead of the fluoride you can use 10 g/l citric acid or 1 g/l conc. sulphuric acid.
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prices depend on the retailer - the price for tin-II-chloride is outrageous at mine, but dithionite and thiorea cost exactly the same.
I have sodium dithionite at my place, using it to de-silver my spent fixer.
In doses of 500g I pay 7 or 8EUR per pack.
Side story - I am just returning from Photokina and spoke with the Foma guys. They will look into making Fomapan R100 in rollfilm and I showed them a bad mistake in their german instruction sheet. It said to prepare 30ml of sulphuric acid, add 270ml of water to it... no, not a good idea, is it?
One guy went to the back room and pulled out a box of their reversal kit, I showed it to them in print. Once they realised what I was talking about the man stuffed the instruction sheet, closed the box...
and handed it over the counter. "For you. THANKS a lot, that could have ended up bad!". Well, I had to carry it all day, but... nice. ;-)
I'm surprised you guys didn't jump at the opening I left by implying that I have only made 2 mistakes.