The storage and operational life of instrument ball bearings are greatly improved by barrier films—thin films of fluorinated organic polymers applied to specific metallic areas to prevent lubricant migration. Current difficulties in determining barrier-film location, a factor critical to effective barrier performance, are shown to be alleviated by incorporating long-lived fluorescent indicators in the solutions used to prepare the barriers. The resulting films exhibit useful levels of fluorescence under ultraviolet radiation after solidificationin situand prolonged storage at relative humidities below 50 percent. Fluorescence decreases with storage at high humidities, but moisture sensitivity of the indicator provides no greater a limitation than does corrosion sensitivity of the bearings. Retention experiments with chlorinated silicones and contact angle measurements with additional liquids show barrier performance to be unaffected by the fluorescent indicator. Therefore, incorporation of long-lived fluorescing components in barrier film formulations is recommended.Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference held in Atlanta, Georgia, October 16–18, 1973