What is a common characteristic of fluorescent penetrants?

Fluorescent penetrants are designed to emit bright fluorescence under ultraviolet (UV) light, which is essential for their effectiveness in the liquid penetrant testing process. This characteristic allows for the detection of defects that are otherwise difficult to see under normal lighting conditions. The UV light activates the fluorescent properties of the penetrant, making it glow, thereby highlighting any cracks, porosities, or other surface defects.

While fluorescent penetrants may emit some visibility in ambient light, they excel under UV lights, which is critical to providing clear indications of defects. This property distinguishes them from other types of penetrants that may be visible in normal lighting.

The attributes of fluorescent penetrants further include a variety of formulations, but they are not exclusively oil-based, as they can also be found in water-soluble forms. Additionally, they can be used in conjunction with water-based methods in certain applications; hence, they are not restricted to only oil-based formulations or incompatible with water.