The information for this technical article has been supplied by Rita & Major Pearle of Colchester and collated and re-vamped by Ron Knowles.
FIRST DEVELOPMENT & ADJUSTMENTS. (pH 12.) Shortened development time favours the top one or two layers and so increases the cyan in the finished slide. To increase yellow-magenta: increase the amount Potassium Iodide and Potassium Bromide by about 25% or increase the processing time by 20 seconds or increase the temperature by 2 deg.F.
To decrease yellow, increase the Potassium Thiocyanate by 0.1gm. The Iodide level increases with each film processed. To increase yellow decrease the Pot Thiocyanate by 0.1gm. Potassium Bromide restrains fog in the first developer allowing a higher maximum density (D-max!), blacker blacks, to be formed in the colour developer.
Potassium Thiocyanate functions as a highlight clearing agent and is best made up as an aqueous solution as it absorbs water vapour from the air. Substitute 1.2gm. of Potassium Thiocyanate for one gramme of the Sodium Thiocyanate.
The temperature of the first developer is especially critical. It is best to use the water bath at one or two degrees above processing temperature to allow for the possible drop during the change-over from one solution to the next.
WASH...STEP TWO. Developer activity is designed to taper off gradually. During the three minute wash it ceases first in the yellow layer; next in the magenta dye-forming layer and finally in the cyan-forming layer. This is built in as part of the E6 process. If a stop bath is used instead of the wash it could result in more magenta and cyan dyes forming during colour development and a bluer colour balance.
REVERSAL...STEP THREE (pH 5.75). Stannous Chloride is a so-called reducing agent which can convert silver halides into metallic silver but this reaction takes place only in alkaline solutions - as colour developer - so no water rinse should be used between the reversal bath and the colour developer. The Chelating agent helps to keep the Stannous Chloride in solution and prevents precipitation. The p. Amino-phenol acts as a preservative against aerial oxidation of tin (Stannous Chloride).
COLOUR DEVELOPER...STEP FOUR (pH 11.9 - 12.00). Excess Sodium Sulphite in this solution will react with the oxidised developing agent reducing the amount of dye formed resulting in `thin` slides. If there is too little the colour developer oxidises more rapidly. Citrazinic Acid reacts with oxidised development agent to produce a soluble dye which easily washes out of the film. Contrast and colour saturation will increase as you use less of this compound and vice- versa. Too little may give a green cast and too much a thin and pinkish slide.
Colour developer pH has the greatest effect on neutrality of the grey. Increasing the pH results in less blue but increases colour saturation and colour fog in highlights. HS 104 is a development accelerator. Colour development and dye formation apparently happens in three stages.
(1) Silver Halide plus developing agent showing reactive amino(NH2) group gives silver metal image plus Oxidised developing agent plus negative bromide.
(2) Leuco dye formation - Oxidised developing agent plus colour coupler gives leuco dye.
(3) Oxidisation of leuco dye to dye leuco dye plus oxidizing agent (another hydrogen atom gives stable dye.
The Leuco dye is a reduced form of the actual stable dye. It contains EXTRA hydrogen atoms. The Leuco form is either colourless or weakly coloured and seems to become a problem only in the cyan layer where it may only be partly oxidised in the colour developer and partly in the bleach.
CONDITIONER...STEP FIVE... (pH 6.15). Since Ferric E.D.T.A. Bleaches are less potent than Ferricyanide bleaches they need to be accelerated and the conditioner modifies the silver metal image to facilitate this.
BLEACH...STEP SIX...(pH 5.7). Bleaching converts metallic silver back to silver halide so that it can be dissolved in the fixing bath. Ferric Ammonium E.D.T.A is now sold as a liquid concentrate. When the pH of the bleach is too high - alkaline - bleach rate is slowed down considerably and could lead to residual silver being left in the film. If the pH is too low (acid) it could cause the formation of leuco cyan dye in which case the film becomes reddish in colour... but is usually correctable by re-bleaching in fresh bleach.
Silver bleaching is an oxidation-reduction reaction. Silver metal is oxidised to silver ion which combines with bromide to form silver bromide.
Ferric E.D.T.A. is the compound which is reduced. The Ferric (iron) changes from one electrical charge state to another creating ferrous E.D.T.A. as a by-product. It is usually necessary to aerate the solution to obtain almost 100% reversion of the inactive ferrous E.D.T.A. to a ferric form.
FIXER...STEP SEVEN...(pH 6.5). Ammonium Thiosulphate is the fixing agent which is more soluble and more rapid than the Sodium Thiosulphate of yesteryear.
------ COMPUTER BUFF NEWS ------
For computer repairs I couldn`t recommend more Analogic Computers (UK) Ltd, Unit 6, Ashway Centre, Elm Crescent, Kingston-Upon-Thames, Surrey, KT2 6HH, Tel. 081-546-9575. "One chap drives from Grimsby" Couldn`t say more. Most repairs carried out while you wait. Also Door to Door courier (£5 + VAT). Don`t throw away your spent Printer Ink cassettes... For just £1 Freaks Public Domain Library, 29. Leap Valley Crescent, Downend, Bristol. BS16 6TQ, will re-ink them, good as new. Save pounds and the environment. Ed.
