What brightness level must Level 3 and Level 4 penetrants maintain?

• A. 50% brightness
• B. 60% brightness
• C. 70% brightness
• D. 80% brightness

Answer: (C)

Brightness control in liquid penetrant inspection is about making indications stand out clearly under viewing conditions. For higher-sensitivity levels, the brightness must be set to a standard level so tiny surface flaws don’t hide in the background or under glare. Level 3 and Level 4 penetrants are specified to be maintained at 70% brightness. This value provides the right balance: it’s bright enough to reveal small, subtle indications, yet not so bright that images wash out or become inconsistent under different lighting. If brightness is too low, faint indications may be missed; if it’s too high, noise and glare can obscure real flaws. Keeping to 70% ensures consistent detection sensitivity across inspections. Calibration with a standard reference or meter helps maintain this level reliably.