E-6 process
The E-6 process is a chromogenic
Chromogenic refers to color photographic processes in which a traditional silver image is first formed, and then later replaced with a colored dye image.- Description :...

 photographic process
Photographic processing
Photographic processing is the chemical means by which photographic film and paper is treated after photographic exposure to produce a negative or positive image...

 for developing Ektachrome
Ektachrome is a brand name owned by Kodak for a range of transparency, still, and motion picture films available in most formats, including 35 mm and sheet sizes to 11x14 inch size. Ektachrome has a distinctive look that became familiar to many readers of National Geographic, which used it...

, Fujichrome and other color reversal (slide) photographic film.

Unlike some color reversal processes (such as Kodachrome
Kodachrome is the trademarked brand name of a type of color reversal film that was manufactured by Eastman Kodak from 1935 to 2009.-Background:...

K-14 process
K-14 was the developing process for Kodak's Kodachrome transparency film; the last version having been designated Process K-14M. The process differed significantly from its contemporary, the E-6 process, in both complexity and length. Kodachrome film has no integral color couplers; dyes are...

) that produce positive transparencies, E-6 processing can be performed by amateurs with the same equipment that is used for processing black and white negative film or C-41
C-41 process
C-41 is a chromogenic color print film developing process. C-41, also known as CN-16 by Fuji, CNK-4 by Konica, and AP-70 by AGFA, is the most popular film process in use, with most photofinishing labs devoting at least one machine to this development process....

 color negative film. The process is sensitive to temperature variations; a tempered water bath is recommended to stabilize the temperature at 100.0 °F for the first developer and first wash to maintain process tolerances.


The E-6 process superseded Kodak's E-3
E-3 process
The E-3 process is a now outdated process for developing color reversal photographic film, which was invented in the early 1950s....

 and E-4
E-4 process
The E-4 process is a now outdated process for developing color reversal photographic film.The process is infamous for its use of the highly toxic reversal agent Tertiary Butyl-Amine Borane . The use of the reversal agent permits processing of the film without the manual reexposure that its...

 processes. The E-3 process required fogging with light to accomplish image reversal and produced transparencies that faded quickly. The E-4 process used polluting chemicals, such as a highly toxic reversal agent Tertiary Butyl-Amine Borane (TBAB).

Process variations

There are two versions of the E-6 process. Commercial laboratories use a six-bath chemical process. The 'hobby' type chemistry kits, such as those produced by Tetenal, use three chemical baths that combine the color developer and fogging bath solutions, and the pre-bleach, bleach and fixer bath solutions. The three-bath process has a discrete color developer step in between. However, the three-bath version of the process suffers from poor process control, with color shifts and color crossover, mainly because of insufficient bleaching, fixing or both in the bleach-fixer ("blix") stage.

Six-bath process version

The steps for developing color transparency films using process E6 are:
  • First developer bath: 6:00 @ 100.0 °F. This uses a potassium hydroquinone monosulfate - phenidone
    Phenidone is an organic chemical compound whose primary use is as a photographic developer. It has five to ten times the developing power as Metol. It also has low toxicity and, unlike some other developers, does not cause dermatitis upon skin contact.Phenidone is Ilford's trademark for this...

     black & white film developer, with the preferred form of phenidone being 4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidinone (13047-13-7). The first developer forms a negative silver image in each layer of the film. The first developer is time and temperature sensitive because it controls contrast.

  • First wash: Water stop bath, 2:00 @ 100.0 °F. This step once used an acetic acid stop bath, but was replaced with a water-only bath for process economy, with concomitant slight reduction of first developer strength.

  • Reversal bath: 2:00 @ 96-103 °F. This bath prepares the film for the color developer step. A chemical reversal agent is absorbed into the emulsion, which is instantly effective. The reversal step can also be carried out using 800 footcandle-seconds (8.6 klx·s) of light - this variation is used by process engineers to troubleshoot reversal bath chemistry problems such as contamination and issues of low tank turnover as process volumes decline.

  • Color developer bath: 6:00 @ 96-103 °F. This step is carried out to completion. The developer contains CD-3 developing agent, and acts upon the chemically exposed silver halide that was not developed in the first developer to form a positive silver image. The metallic negative silver image formed in the first developer has no part in the reaction of this step. As the color development progresses, a metallic positive silver image is formed and the color developing agent is oxidized. Oxidized color developer molecules react with the color couplers and color dyes are formed in each of the three layers of the film. Each layer of the film contains different color couplers, which react with the same oxidized developer molecules but form different color dyes. Variation in color developer pH causes color shifts on the green-magenta axis with Kodak E100G & E100GX and Fujichrome films and on the yellow-blue axis with older Ektachrome films.

  • Pre-bleach bath: 2:00 @ 90-103 °F. This bath was previously called "conditioner", but was re-named pre-bleach in the mid-1990s to reflect the removal of formaldehyde from the process used in the final rinse. In this solution, formaldehyde
    Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

     acts as a dye preservative and EDTA
    Ethylenediaminetetraacetic acid, widely abbreviated as EDTA , is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve limescale. Its usefulness arises because of its role as a hexadentate ligand...

     is used to "kick off" the bleach. The pre-bleach bath relies on carry-over of the color developer to function properly, therefore there is no wash step between the color developer and pre-bleach baths.

  • Bleach bath: 6:00 @ 92-103 °F. This is a process-to-completion step, and relies on carry-over of pre-bleach to initiate the bleach. The bleach converts metallic silver into silver bromide
    Silver bromide
    Silver bromide , a soft, pale-yellow, water insoluble salt well known for its unusual sensitivity to light. This property has allowed silver halides to become the basis of modern photographic materials. AgBr is widely used in photographic films and is believed by some to have been used for making...

    , which is converted to soluble silver compounds by the fixer. During bleaching, iron (III) EDTA is converted to iron (II) EDTA (Fe3+ EDTA + Ag + Br→ Fe2+ EDTA + AgBr) before fixing. Kodak also has a process variant which uses a higher concentration of bleach and a 4:00 bath time; but with process volumes declining, this variant has become uneconomical.

  • Wash step (optional): Rinses off the bleach and extends the life of the fixer bath. This wash step is recommended for rotary tube, sink line and other low volume processing.

  • Fixer bath: 4:00 @ 92-103 °F. This is a process-to-completion step.

  • Second fixer stage (optional): Using fresh fixer. The archival properties of film and paper are greatly improved using a second fixing stage in a reverse cascade. Many C-41RA (rapid access) minilab processors also use 2 stage reverse cascade fixing for faster throughput.

  • Final wash: 4:00 @ 92-103 °F.

  • Final rinse: 1:00 @ 80-103 °F. Up until the mid 1990s, the final rinse was called a stabilizer bath, since it contained formaldehyde
    Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

    . Currently, the final rinse uses a surfactant
    Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...

    , and miconazole
    Miconazole is an imidazole antifungal agent, developed by Janssen Pharmaceutica, commonly applied topically to the skin or to mucus membranes to cure fungal infections. It works by inhibiting the synthesis of ergosterol, a critical component of fungal cell membranes...

    , an anti-fungal agent.

  • Drying: Drying in a dust-free environment.

External links

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