What property should a penetrant possess to effectively highlight defects?

For a penetrant to effectively highlight defects, possessing fluorescent properties is essential. Fluorescent penetrants are designed to absorb ultraviolet (UV) light and then re-emit it as visible light, which makes even small defects more visible against a contrasting background. This capability allows for the easy identification of cracks, voids, or other discontinuities that may not be seen clearly with the naked eye or with non-fluorescent penetrants.

The effectiveness of fluorescent penetrants primarily rests on their ability to stand out or glow under UV light, enabling inspectors to quickly and accurately assess the integrity of materials. This is particularly useful in non-destructive testing (NDT) where precise detection of flaws is crucial for safety and reliability in various applications, such as in aerospace or automotive industries. This property greatly surpasses other characteristics like viscosity or volatility in terms of highlighting defects effectively.