Shooting and processing out-of-date film engages the core of experimental photography. Part chance, part experience, part research, processing old film engages new approaches to photography through trial and error.
After the adoption of the 35mm film width in 1909 as the international standard gauge for movie picture systems, 35mm still cameras were introduced to exploited the availability and advantages of 35mm cine film stock. With new 35mm cameras, photographers could take a large number of photographs without the inconveniences of reloading new film. Small, fast, and highly portable, these new camera systems which were marketed to the burgeoning amateur market. Several new designs accommodated up to 50 feet of Kodak cine film, enough film for 400 exposures.  After World War I, 35mm film became the most popular film format for still cameras, and spawning hundreds of film types and film brands.
In the era when feature films were created exclusively with film,  movie studios purchased large supplies of color cine film to lessen graphic continuity issues resulting from mixing different film emulsions. In the 1970’s, numerous independent film labs and film suppliers marketed repackaged cine film under individual labels, typically remarking Kodak’s most popular cine film, Kodak 5248 . As a promotion two of the most successful companies, Dale Laboratories and Seattle FilmWorks, sent film free to photographer across the country to encourage photographers to use their company’s processing services and offered film free with processing orders. Initially, much of this film was rebranded Kodak 5248 cine film, however traditional color negative film was also shipped to photographers.
I recently discovered several rolls of long out-of-date Dale Laboratories “9100” 35mm color film at the bottom my film storage box. Given the indeterminate age of the “9100” film, I felt these rolls offered an excellent opportunity for experimentation. The recommended processing for Dale Laboratories “9100” 35mm color film is “Process CNK-4 / ECP-2”.  Given processing recommendation, I first believed the “9100” film was repackaged Kodak Vision (2383) Color Print movie film, an Estar base cine film stock, which was also sent free to photographers as a promotion.   The recommended processing for Kodak Vision 2383 Color Print Film is process ECP-2.  However, after deeper research tracking the DX number on the film canister, I discovered my roll of “9100” film is rebranded Ferrania Imaging Color FG100 color negative film with an approximate manufacturing date of 1998.   
In the set of images attached to this post, I photographed in San Francisco’s Golden Gate Park in shady conditions and in the Barbro Osher Sculpture Garden at the De Young Museum in partial sun. I was especially taken with the unusual mixing of yellows and magentas, a result of color shifts from the outdated film emulsion. Exposed at ISO 100 using the built in light meter on an Olympus OM-2 equipped with a Tamron 28-200 zoom lens, the film maintained good detail and exhibited a pleasant film grain. The film was hand processed in standard C-41 color chemicals, using a freshly mixed Unicolor C-41 chemistry to “cross process” the film and scanned on a Nikon CoolScan 9000 film scanner.
I do plan to continue experiments with the remaining stocks of “9100” film. I have approximately 8 rolls left of this particular film stock. Checking Ebay, as well, there appears to be plentiful stocks of 9100 film still available. Outdated supplies of Seattle FilmWords film is also remains available. 
 Todd Gustavson, Camera, P. 210.
 CNK-4 is Konica’s C-41 process; and ECP-2 is Kodak’s cine film development process.
 Seattle FilmWorks was renamed PhotoWorks in 1999, and discontinued all film processing in 2010.
Dale Laboratories remains a highly regarded film processing lab located in Hollywood, Florida.