K-14 process
From Wikipedia, the free encyclopedia
K-14 is the name of the developing process for Kodak's Kodachrome transparency film. The process differs significantly from the other color transparency processes in use today in terms of both complexity and processing steps. Kodachrome film does not have integral color couplers; dyes are added during processing, each in a separate step. The process, which due to its complexity cannot be performed by amateur photographers, is not widely available.
[edit] Steps
The processing cycle is as follows:
- Backing removal
- An alkaline bath softens the cellulose acetate phthalate binder. A spray wash and buffer removes the backing.
- First Developer
- All exposed silver halide crystals are developed to metallic silver. The yellow filter layer becomes opaque because it has a combination of Lippmann emulsion (very tiny grains) and Cary Lea silver (metallic silver particles that are small enough that they are yellow rather than gray.)
- Wash
- Red light re-exposure through the base
- This makes the remaining undeveloped grains in the cyan layers developable.
- Cyan developer
- The solution contains a color developer and a cyan coupler. These are colorless in solution. After the color developer develops the silver, the oxidized developer reacts with the cyan coupler to form cyan dye. The dye is much less soluble than either the developer or the coupler so it stays in the film.
- Wash
- Blue light re-exposure from the top
- This makes the remaining undeveloped grains in the yellow layers developable. The now opaque yellow filter layers prevents the blue light from exposing the magenta layers.
- Yellow developer
- Analogous to the cyan developer.
- Wash
- Magenta developer
- This contains a chemical fogging agent that makes all of the remaining undeveloped silver developable. If everything has worked right, nearly all of this silver is in the magenta layers. The developer and magenta coupler work just like the cyan and yellow developers to produce magenta dye that is insoluble and stays in the film.
- Wash
- Conditioner
- Prepares the metallic silver for the bleach step.
- Bleach
- Oxidises the metallic silver to silver halide.
- Fix
- Dissolves the silver halide and washes it from the film
- Wash
- Washes the fixer out of the film.
- Rinse
- Contains a wetting agent to reduce water spots.
- Dry
The result is three different color records each with the appropriate dye, just like other color films. The original Kodachrome process in 1935 used dye bleaches and was a far more complicated process. Although the formulas have changed over the years, the basic process steps have followed a similar pattern since the introduction of "selective re-exposure" Kodachrome in 1938.
