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See also Ektachrome for full details of Kodak E-series processes.

The E-4 process is a now outdated process for developing color reversal (transparency) photographic film, which was introduced in 1966.

• Drawbacks

• Steps

• History

• Notes

• References

• External links

• Processing of older Ektachrome films (including Process E-4)

The process is infamous for two reasons:

First, it uses the highly toxic boron hydride-based reversal agent tertiary butyl-amine borane (TBAB).cite-ref-1[a]cite-ref-jacobson80-2-0[1] Early releases of the consumer-sized version of the chemistry provided the TBAB in the form of a tablet, possibly to avoid the possibility of inhalation.cite-ref-talbert-3-0[2] This was later changed to loose powder, likely as a countermeasure against inadvertent ingestion of the substance.

Second, the prehardener agent contains formaldehyde and 2,5-dimethoxytetrahydrofuran,cite-ref-jacobson80-2-1[1] which when mixed generates succinaldehyde, a noxious gas which has been likened to tear gas.cite-ref-talbert-3-1[2] Process E-6 films are hardened during manufacture, eliminating the prehardener step altogether and allowing them to be processed at 100 °F (38 °C).

Ektachrome film has three separate light-sensitive layers; each layer is sensitive to a different group of wavelengths corresponding to red, green, and blue colors. When the film is exposed, each layer records a latent image based on its sensitivity. A yellow filter prevents blue light from exposing the green- and red-sensitive layers, which have some sensitivity to blue light.cite-ref-z119-1-4-0[3]

The E-4 process is faster than E-3; whereas E-3 required 15 steps and up to 70 minutes from start to finish,cite-ref-talbert-3-2[2]cite-ref-e-13-5-0[4] E-4 was completed in approximately 50 minutes over 13 steps.cite-ref-ps-1968-6-0[5] E-4 runs at 85 °F (29 °C),cite-ref-ps-1968-6-1[5] about 10 °F (6 °C) higher than E-3. The temperature tolerance is ±1 °F for prehardener, ±1⁄2°F for the first developer, and ±2–5 °F for all other steps.cite-ref-ps-1968-6-2[5] The ME-4 process was a motion picture variation of the E-4 process.

The major change for E-4 was the inclusion of a chemical reversal agent, which permits processing of the film without the manual re-exposure/fogging step required by the predecessor E-1 / E-2 / E-3 processes.cite-ref-talbert-3-3[2]cite-ref-ps-1968-6-3[5]

Total darkness is required during the first four development steps; normal room light can be used for the remaining steps.cite-ref-ps-1968-6-4[5]

| Step | Step | Step | Schematic | Time (min.) | Temp. | Description |

|---|---|---|---|---|---|---|

| | 1 | Prehardener | | 3 | 85 °F (29 °C) ±1 °F | Tempers film for high-temperature processing |

| | 2 | Neutralizer | | 1 | 83–87 °F (28–31 °C) | |

| | 3 | First developer | | 7 | 85 °F (29 °C) ± 1 ⁄ 2 °F | Conventional black-and-white developer used to transform silver halide crystals exposed in all three layers as a negative image. |

| | 4 | First stop bath | | 2 | 83–87 °F (28–31 °C) | Solution should not be reused for second stop bath (step 7) |

| | 5 | Wash | | 4 | 80–90 °F (27–32 °C) | Running water |

| | 6 | Color developer | | 9 | 83–87 °F (28–31 °C) | |

| | 7 | Second stop bath | | 3 | 83–87 °F (28–31 °C) | Solution should not be reused from first stop bath (step 4) |

| | 8 | Wash | | 3 | 80–90 °F (27–32 °C) | Running water |

| | 9 | Bleach | | 5 | 83–87 °F (28–31 °C) | Convert metallic silver to soluble particles |

| | 10 | Fixer | | 6 | 83–87 °F (28–31 °C) | Dissolve silver particles, which can be recovered after processing |

| | 11 | Wash | | 6 | 80–90 °F (27–32 °C) | Running water |

| | 12 | Stabilizer | | 1 | 83–87 °F (28–31 °C) | |

| | 13 | Dry | | var. | <110 °F (43 °C) | |

E-4 processed film is color stable for about 30 years.cite-ref-7[6]

The process largely was phased out in 1976 with the introduction of the E-6 process, which is more environmentally friendly due to its lack of toxic chemicals. E-6 avoids the use of TBAB by adding a separate reversal bath containing the tin salt stannous chloride.

The E-4 process has been discontinued since 1996; after 1976 it was used solely for Kodak IE color infrared film,cite-ref-8[7] due to a legal commitment by Kodak to provide process support for 30 years after introduction. Kodak discontinued E-4 processing in 1985, but independent photofinishers continued to support the process.cite-ref-9[8] The E-4 chemicals were reverse-engineered and substitute formulae were published in the British Journal of Photography Annual in 1977.cite-ref-jacobson80-2-2[1]

cite-note-1a. ↑ Not to be confused with tetra-n-butylammonium bromide, which also is abbreviated as TBAB.

cite-note-jacobson80-21. ↑ citerefjacobson-kurt-i-jacobson-ralph-eric1980Jacobson, Kurt I.; Jacobson, Ralph Eric (1980). "Processing Colour Films". Developing: The Negative Technique (Eighteenth revised ed.). London: Focal Press. pp. 363–383. ISBN 0-240-44770-0. Retrieved 24 August 2023.

cite-note-talbert-32. ↑ citereftalbert-michaelTalbert, Michael. "Kodak Ektachrome Colour Transparency films". Photo Memorabilia. Retrieved 24 August 2023.

cite-note-z119-1-43. ↑ "Process E-6 Using KODAK Chemicals, Process E-6 Publication Z-119 | Chapter 1: Processing solutions and their effects" (PDF). Kodak. Archived from the original (PDF) on August 25, 2005.

cite-note-e-13-54. ↑ Kodak Ektachrome Film, Publication No. E-13. Eastman Kodak Company. 1955.

cite-note-ps-1968-65. ↑ citerefwahl-paul1968Wahl, Paul (April 1968). "Kodak's new E-4 kit: 50-Minute Cure for People Afraid to Develop Their Own Color Film". Popular Science. pp. 130–131.

cite-note-76. ↑ "Ektachrome: A Look Back". 25 January 2017.

cite-note-87. ↑ citerefensanian-armand1988Ensanian, Armand (July 1988). "Inner Visions". Popular Mechanics. pp. 100–101. Retrieved 24 August 2023. Color IR film has one drawback. It is not readily processed because it requires the old E-4 chemistry.

cite-note-98. ↑ citerefrothschild-norman1985Rothschild, Norman (December 1985). "Pop Photo Snapshots: Bad and good news from Kodak". Popular Photography. pp. 28–32, 114. Retrieved 24 August 2023. Eastman Kodak no longer offers processing for E-4 films such as Ektachrome Infrared and Kodak Microphotography color-slide films. However, there are more than a dozen independent labs in the U.S. that offer this service.

• Kodak specifications for hand mixing of chemistry

• "More than you want to know about E-4". 19 May 1995.

• Film Rescue USA and Canada

• Rocky Mountain USA