As the document processing world moved to computerized records, Kalvar was no longer in demand, and vesicular microfilm is now only made upon request.
The physical robustness of the Mylar base was an advantage, allowing it to be handled far longer than conventional silver-halide films of the era (early 1960s).
This led to an antitrust suit being filed by the Federal Trade Commission in 1981, and Xidex agreed to sell off the entire Kalvar side of their business (they had several others) in 1983,[3] which failed soon after.
[4] Because the film was sensitive to UV only, it could be easily handled under normal incandescent lamps with no need for a darkroom, although for archival storage it was placed in UV-protective boxes.
This left an inert negative vesicular image simply composed of nitrogen filled bubbles in a relatively stable plastic.
A direct positive print could be made by using a much more gas permeable matrix which, after initial exposure, allowed the nitrogen in the exposed areas to quickly diffuse out into the atmosphere without bubble development.
This would be followed by a quick overall re-exposure of the film to a high powered xenon flash lamp which would disrupt the remaining unexposed diazonium sensitizer.
In the production process, a solution of Saran dissolved in an organic solvent and containing a small amount of a diazo compound was coated onto a substrate of Mylar.
In a second process called “cycling,” it was run through a tank of very hot water which created a fog of small holes in the Saran layer.
Since Kalvar film used no chemicals for processing, the equipment needed to use it was limited only by the speed of the transport mechanism and the power of the ultraviolet light.