TECHNICAL COMMENT/UPDATE

By Lawrence Edwards. B. Sc., C. Chem. M.R.S.C.

I do not find myself with much time to write for the CRCN, usually because of the working and photography, E6 and now colour printing.
However, I am on holiday in Torremolinios and it is pouring rain.

I am prompted into writing firstly because of a possible misunderstanding over the reversal bath. The formula published in the
January (89) CRCN is essentially the one that I use which resulted from the chemical analysis of the genuine Kodak chemicals. It is
therefore Kodak`s process.

I have tended to stick as closely as makes sense to the Kodak conditions for spiral tanks.

The conditions complied by Ron Croad were after some discussion, and are essentially those by Kodak. However there is a little
ambiguity. The "brief rinse" after the reversal should refer to tank & lid only, not the film emulsion or spiral. I normally do this to minimise
carry over. I also shake off the surplus from spiral into sink. It is probably not necessary but may extend the life of the colour developer if
part used. With my Jobo CPE2 processor the latter is not easily facilitated so I have not bothered. My thinking on the removal of the
excess was that continuous processing machines use squeegee to minimise carry over.

Kodak are quite clear on this matter and I quote from their Z119 professional manual: "Use no wash between the reversal bath and
colour developer steps because complete reversal requires that the reversing agent be in the emulsion when the film enters the colour
developer. Ron has tried, just for interest, rinsing after all stages and found no detrimental effects. However to be sure I would stick to the
Kodak as a routine.

The other "Brief rinse" listed in the Club conditions should also not include the film emulsion especially after the conditioner. Some of the
thioglycerol in the conditioner needs to be carried over into the bleach to catalyse (speed up) the action. Kodak say "Use no wash
between Conditioner and the Bleach because conditioner carry-over is a necessary component of a seasoned bleach conditioner. Also
completion of the conditioning action depends on the presence of conditioner in the emulsion when the film contacts the bleach".

Kodak are not so dogmatic over other transfers. I have deviated from the Kodak conditions in that they do not wash after colour
development. The Club conditions list a one minute wash here. I just give two quick (15 secs) washes at 38C then in with the conditioner
ASAP. I feel this is beneficial but have little evidence. It may help if the bleach is to be kept for several weeks part used (reduces stain?).

Incidentally, the club conditions state for some baths "Invert once then leave". This is a deviation from Kodak conditions. I would
recommend that agitation be continuous for the first 15 secs of ALL baths. The reversal, conditioner and stabiliser may then be left.

The formula can be made up and stored for long periods as concentrates e.g. 20x for reversal. I have information for those interested if
they contact me. Some minor modifications are required. These should not be attempted until the process is mastered for the working
solutions.

Those who use kits like the Chrome 6 may well wonder how these work without the conditioner. I believe they may incorporate a catalyst
in the Blix instead. (mercapto 1,2,4 triazole).

Writing is becoming difficult because the electricity has gone off again caused by lightening. So I will finish by mentioning one or two
things I have been doing. I now have a small darkroom at home and have bought a used Philips PCS130 colour enlarger. C41/EP2 negative
processes have been like a holiday after E6. i.e. they have worked first time. I have not done any Cibachrome yet but have just tried the
Kodak Ektachrome 22 paper for prints from slides. Results are excellent. The chemicals have some similarity to those used in E6. Processing
is the Kodak R3 process done at 38C. Chemical or light reversal can be used.

I am pleased to discuss any of these matters - address in January & October CRCN. Phone Leeds 01924-223226.