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Monobath Invention

 Monobath Processing for Lithographic Film – The Freedman Monobath


What is Photographic Monobath Chemistry?

A monobath is a single liquid that chemically processes film. Monobaths are commonly used for continuous tone film and paper. In fact the Polaroid process itself used a viscous monobath. Monobaths have several benefits:

  • Only one chemical is needed.
  • Because the developing process is also the fixing and finishing process, it is impossible to accidentally over-develop a photo.


What was Discovered and What is New about The Freedman Monobath?

A drawback is that monobaths did not work with what are called infectious developing films such as those used in printing and publishing.  With contone film, a photon of light hits silver halide within the emulsion. When the contone film is processed, the developer chemical acts only on the area struck by light. With the steep gamut, high-contrast lithographic films used in the graphic arts, the development process is termed “infectious” because the entire silver halide grain hit by the photon develops with lithographic film, not only the portion of the halide grain that the light hits. Until my work, monobath chemistry did not work with graphic arts lithographic film.

While an undergraduate student at Rochester Institute of Technology (RIT) in 1971, I discovered an organic chemical that stopped and fixed lithographic films while intermixed with active film developer chemistry. After extensive research and testing, I produced a practical, working infectious processing monobath incorporating this organic chemical.


Dubbed the Freedman Monobath, my process has advantages over conventional film processing systems:

  • It uses a smaller processing area, saving lab floor space and expense.
  • It enables the developed film to be ready for print production twice as fast as conventional processing.
  • It produces less waste water and chemical waste.
  • It retains all the benefits of a conventional monobath, mentioned above.

As the first working monobath for graphic arts films, my invention was a major breakthrough.

Click here to see me in the photochemistry lab working on the lithographic monobath.


The Freedman Monobath Process

The exposed film is placed in a developing tank containing the Freedman monobath solution. The liquid is then agitated with nitrogen burst bubbles on both sides of the film. The developer chemistry within the monobath very quickly develops the film, while the organic chemistry within the same liquid stops and clears the film. Think of it as a relay race around a track: the developer runs the first half of the race, then hands off the baton to the fix which completes the course. When processing is complete, the film is simply spray washed in a water sluice and then dried. The lithographic film is processed faster, more economically, and with a “green” chemistry that minimizes the processing waste entering the environment.


What Resulted from the Invention?

The Eastman Kodak Company made me an Eastman Kodak Research Scholar, paying for my undergraduate studies at RIT and supporting my research and experimentation. In my senior year, thanks to my monobath process, I was awarded a 3M Graduate Research Fellowship to the university of my choice. Although the Freedman Monobath was never commercialized as part of an arrangement with Eastman Kodak, it paid for my college education in the end.


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