What is the most commonly used method for removing nonwater-washable visible dye penetrant from a test specimen surface?

The most commonly used method for removing nonwater-washable visible dye penetrant from a test specimen surface involves hand wiping. Hand wiping with an appropriate solvent or cloth absorbs and removes the penetrant effectively, which is essential for ensuring proper inspection results. This method allows the operator to control the amount of pressure applied and the thoroughness of the cleaning process, ensuring that excess penetrant is removed without damaging the surface of the specimen.

In the context of the other methods, wiping with a damp cloth or using a water spray are less suitable for nonwater-washable penetrants, as these products are specifically designed to require a solvent-based cleaner for removal. Applying additional penetrant is counterproductive, as it would only add more material to the surface, complicating the inspection process rather than facilitating it. Therefore, hand wiping is regarded as the most reliable and effective technique for this specific situation.