Spark Holiday Testing
The spark holiday test is used to check for pinholes, voids, discontinuities or “holidays” in surface coatings.
When a voltage is applied on metal fibers that are temporarily placed on the coated surface. Where indications are present, a circuit will be created that allows electrical current flow, and a spark will inform the inspector of the “holiday”.
Inspectors are trained to apply the appropriate voltage and potential safety hazards caused by sparking. Due to coating thickness being a factor, voltage is applied by starting with lower voltage, and increasing. This is done until the appropriate amount of current is applied given the required thickness of the coating. With high voltage, thickness of up to 25 mm can be tested.