E-4 process

The E-4 process is a now outdated process for developing color reversal (transparency) photographic film.

The process is infamous for two reasons:

First, its use of the highly toxic reversal agent tertiary butyl-amine borane (TBAB) (not to be confused with tetra-n-butylammonium bromide, which also has TBAB as abbr.) – as of all boron hydrides. Early releases of the consumer-sized version of the chemistry provided the TBAB in the form of a tablet. This was later changed to loose powder (likely as a countermeasure against inadvertent ingestion of the substance). The use of the reversal agent permits processing of the film without the manual reexposure that its predecessor E-3 required. Kodak's official E-6 process, which replaced Process E-4 for almost all applications, avoids the necessity of TBAB by adding a separate reversal bath containing the tin salt stannous chloride.

Second, the first two steps in the process are prehardener and neutralizer. When the prehardener is neutralized, a noxious gas, which has been likened to tear gas, is generated. Process E-6 films are hardened during manufacture, eliminating the prehardener step and allowing them to be processed at 38°C (100°F).

ME4

ME4 or ME-4 may refer to: