BLACK & WHITE REVERSAL

Ron Knowles (Area 11).

It may OCCUR to members that to refer to a black and white process in our hitherto aptly named Club as a little bizarre - indeed somewhat irrelevent - but I offer no apology for I believe there may well be room for a spot of diversity within our ranks in certain circumstances.

In my own case I recently came across some old, but none-the-less acceptable, B&W whole plate prints. All are irreplaceable so what better than to have them included, as transparencies, in my collection of colour slides? maybe there are other members who would also like to include valued pictures preserves in this way.

So I battled along a path which has disappointed in the past but this time I feel I have been successful and I am delighted to pass on details of what is really quite a simple process, and includes mostly chemicals which more than likely will already be held by home processors. The exception could well be Potassium Bichromate, the actual reversal agent. This is readily available from Rayco or Photo Chemical Supplies. Both list this as Potassium Dichromate - same difference!

So in hope that there are others out there sufficiently interested to try out the B&W alternative to colour here is the full processing procedure:-

FIRST DEVELOPER (Concentrate) Metol............................................. 4gms. Sod. Sulphite (Anhyd)........... 18,0gms. Hydroquinone........................... 3.5gms. Sod. Carbonate (Anhyd)..........9,3gms. Pot. Bromide (10%Sol)..................5mls. Pot. Thiocyanate (20%).............9.0mls. Water to......................................250mls.

REVERSAL Pot. Bichromate.......................................... 3.0gms Sulphuric Acid (50%)................................ 6.0mls. Water to ..................................................... 250mls. CLEARING BATH. Sod. Sulphite (Anhyd)..............................8.0gms. Water to ..................................................... 250mls.

FIRST DEVELOPER. For use dilute concentrate 1. part to 2. parts of water.

SECOND DEVELOPER. For use dilute concentrate 1. part to 3. parts of water.

FIXER. Ammonium Thiosulphate (60%Sol)...............................................29.0mls. EDTA Disodium Salt..........................................................................0,5mls. Sod. Metabisulphite........................................................................2.25gms. Sod. Hydroxide..................................................................................0,5gms. Water to..............................................................................................250mls.

PROCEDURE FIRST DEVELOPER............................................................... 4.mns @ 75C. RINSE...................................................................................... 3.mns @   "  " BLEACH................................................................................. 2.mns @   "  " RINSE..................................................................................... 2.mns @   "  " CLEARING BATH................................................................. 2.mns @   "  " Reversal. Expose to a 100 watt lamp for around one minute at about 12 inches is ample re-exposure. Remove from spiral.

SECOND DEVELOPER......................................................... 4.mns @ 75F. RINSE..................................................................................... 2.mns @  "  " FIXER......................................................................................2.mns @  "  " WASH.....................................................................................5.mns @  "  "

(1) The film used in my tests have been ORWO 125 ASA and Ilford HP4.
(2) IT IS essential to maintain temperatures - just as in colour processing. Any deviation will de-value the finished slide to a marked degree.
(3) ONE OF the snags I encountered was a lack of contrast with rather `thin` slides. If this trouble is experienced, do as I did, reduce the dilution of one or both of the two developers. There is ample scope for experiment in this process and the developer concentrate I have given is an extremely versatile mixture.
So Have fun!!