Holiday test

Holidays are bare spots in the protective coating applied to surfaces. Testing involves an evaluation of bottom linings after application to aboveground storage tanks. Also called discontinuity detection. Two types of holiday detection are employed. For thin bottom linings under 20 mils dry film thickness, low voltage/wet sponge detectors are specified. For those linings greater than 20 mils dry film thickness, high voltage spark detectors are employed. See also Dry film thickness test.