What is the purpose of using a developer with a visible penetrant?

• A. To provide high contrast for indicating surface defects
• B. To reduce penetrant viscosity
• C. To accelerate drying
• D. To change color of the penetrant

Answer: (A)

The key idea is that the developer creates a high-contrast display of any surface-breaking flaw. After the penetrant has had time to enter defects, the developer is applied and absorbs the penetrant that has seeped out of those flaws, bringing it to the surface as a visible mark against the background. This results in a clear, easy-to-see indication under normal lighting, making even small defects detectable. The developer’s job is to provide that contrast and localization; it isn’t designed to change viscosity, accelerate drying, or change the penetrant’s color.