The oil-and-whiting method is a form of which NDT technique?

• A. liquid penetrant inspection
• B. magnetic particle inspection
• C. radiography
• D. ultrasonic testing

Answer: (A)

The oil-and-whiting method is a form of liquid penetrant inspection. In this approach, a penetrant oil is applied so that it seeps into any surface-breaking cracks by capillary action. After letting it dwell, the excess penetrant is removed and a white developer (whiting) is dusted on. The developer draws the penetrant out of the crack and toward the surface, producing a visible indication against the white background when viewed under proper lighting (or UV light if using fluorescent penetrant). This method relies on liquid penetration and a contrasting developer to reveal cracks, which is the hallmark of liquid penetrant inspection. It’s not based on magnetism, radiation, or ultrasonic waves, which is why the other techniques don’t fit.