Thread: Colour Printing
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Old 11th October 2020, 07:42 AM
John King John King is offline
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Originally Posted by JOReynolds View Post
This is only theoretical - I've not tried it - but once mixed, ferric EDTA (brown bleach) and thiosulphate (fix) will degrade one-another in the presence of oxygen (air). Why not try bleaching in bleach and then fixing in fix? This is, after all, the procedure for film in C41. I can't suggest the timing or temperature but give 50% longer than when the appearance changes. In fact you might consider using C41 bleach and fix. C41 bleach is expensive but can be replenished and used for a long time. Paradoxically, it needs to be aerated (kept in the oxidised state) to work properly.
They do not appear to degrade each other, well not in my experience anyway. Splitting the bleach and fix into 2 seperate elements would make it impractical with my set-up anyway because the NOVA slot processor has only 3 baths. I would then have to have a dish and a heater for the fixer which is totally impractical in my set up. I am pretty certain the Kodak engineers would have taken this into consideration when they formulated the chemicals anyway. It is possible that they have used something else as a buffer to stop any adverse inter-reaction taking place. Kodak may not have had a lot of success in the modern business world, but they are pretty good chemists.

The aeration of the blix is not really convenient in a NOVA, but the developer is constantly being moved around when the paper is agitated. it is not just dipped into the blix and left to bleach out, it is moved constantly up and down and side to side which appears to be enough to carry out the task. I speak from experience not theory. Sometimes in a live situation, theory has to bow to the practical!

As for longevity of the developer and blix, (Kodak only) I have yet to have a problem. I have found that so long as the replenishment rates are strictly adhered to, there is never a problem. Some time ago I actually had the same baths in continual use for over 12 months. Even then it was only to dredge out the sludge at the bottom of each tank slot (with replenishment rate of 10cc per 80 sq ins of paper). I also take an additional precaution where after every session, I clean the tube lids, inside and out and dry them thoroughly. I replace the lids, but then cover the top of the NOVA with cling film which stops most of the evaporation. I have never been one for note taking, but with RA4 I note down the area of every piece of paper I use and ponce 800 sq ins of paper is reached, the developer, stop bath and blix are replenished with 100cc each. (200cc in the case of the stop bath.) One of the few things I am really meticulous about.

Last edited by John King; 11th October 2020 at 08:11 AM.
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