E-6 process
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The E-6 process (sometimes abbreviated to just E-6) is a process for developing color reversal (transparency) photographic film.
Process E-6 is the most demanding photofinishing process in widespread use. It has more steps than the C-41 process used for color negatives. There is little processing latitude because there is no opportunity to correct density or color balance when printing.
It replaced the E-3 and E-4 processes in 1975. E4 used ferricyanide and other chemicals which there were arguments in the press at the time that these could be carcinogenic. The change to E6 as a safer processes was welcomed
These older processes used several toxic chemicals that the US Environmental Protection Agency requested Kodak stop using. The E-3 process used light for reversal, and produced transparencies that faded more quickly with repeated projection or the passage of time.
The K-12 and older Kodachrome processes are more involved than the E-6 process, and are performed only in specialized plants. Each of the three film layers is developed separately, and dyes are added during the process rather than being incorporated in the film base.
There are two families of E-6 processing chemistries. The original and standard is a six chemical step process. The 'rapid' or 'hobby' type chemistries use three chemical steps. Rinses, washes, stop baths and stabilizer (the optional final step of the process) are not counted in the counting of steps described below.
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Process Sequence for E-6 (six step)
- Pre-Warm
- First Developer
- Rinse or Stop bath
- Reversal
- Color Developer
- Conditioner (Pre-bleach)
- Bleach
- Fixer
- Wash
- Stabilizer (Final Rinse)
Process Sequence for E-6 (three step)
- Pre-Warm
- First Developer
- Rinse or Stop bath 1
- Color Developer
- Rinse or Stop bath 2
- Bleach-Fix
- Wash
- Stabilizer (Final Rinse)
Solutions for a three step process
First developer
- Sodium hexametaphosphate (Calgon) 2.0 g
- Sodium sulphite, anhydrous 39.0 g
- Potassium carbonate, anhydrous 14.0 g
- Sodium bicarbonate 12.0 g
- Phenidone 0.6 g
- Hydroquinone 6.0 g
- Sodium bromide 2.2 g
- Sodium thiocyanate 1.0 g
- Sodium hydroxide 3.3 g
- Potassium iodide, 0.1 per cent solution 4.5 ml
- Water to 1.0 litre
Stop bath 1
- Sodium acetate, anhydrous 30.0 g
- Acetic acid, glacial 6.0 ml
- Water to 1.0 litre
Colour developer
- Sodium hexametaphosphate (Calgon) 2.0 g
- Trisodium phosphate crystals 36.0 g
- Sodium hydroxide 3.0 g
- Sodium sulphite, anhydrous 4.5 g
- Sodium bromide 0.65 g
- Potassium iodide 0.1 per cent solution 30 ml
- Sodium thiocyanate 1.3 g
- Citrazinic acid 1.25 g
- CD3 11.0 g
- Water to 1.0 litre
Stop bath 2
As for Stop Bath 1, but do NOT interchange them after use
Bleach
- Potassium ferricyanide 80.0 g
- Potassium bromide 20.0 g
- Disodium phosphate, anhydrous 12.0 g
- Acetic acid, glacial 5.0 ml
- Water to 1.0 litre
Fixer
- Sodium thiosulphate, crystals 200.0 g
- (or anhydrous 125.0 g)
- Sodium sulphite, anhydrous 5.0 g
- Sodium metabisulphite 0.5 g
- Water to 1.0 litre
Stabiliser (optional)
- Formaldehyde, 40 per cent 5.0 ml
- Wetting agent 1.0 ml
- Water to 1.0 litre