In the oil and whiting LPI method, what is the sequence used to prepare the surface?

• A. An object is submerged in oil diluted with kerosene, then removed and coated with whiting to provide a white background
• B. An object is painted with red dye and dried
• C. An object is heated then cooled rapidly
• D. An object is scrubbed with soap and water

Answer: (A)

In this LPI method, the surface is prepared to be both clean and highly contrastive so flaws can be seen clearly. The oil diluted with kerosene first wets and cleans the surface, removing contaminants and reducing surface tension so the penetrant can enter any flaws more effectively. After the surface is wiped clean of excess oil, a white powder called whiting is applied to create a white background. That white background provides the needed contrast for the penetrant, so any indications appear as reddish lines on a bright field. The other options don’t establish this clean, well-wetted surface followed by a white background, which is essential for detecting indications with this method.