Liquid Penetrant Testing Level 1 (PT-1) Practice Exam

What color penetrant is often used for surface inspections in fluorescent penetrant testing?

1. Red

2. Green

3. Yellow

4. Blue

The correct answer is: Green

In fluorescent penetrant testing, the penetrant is specially formulated to absorb and fluoresce under ultraviolet (UV) light. Green is a common color for these penetrants because it produces a strong contrast against the background surfaces when viewed under UV illumination. The brightness of the fluorescent green under UV light makes it easier to detect even very fine defects such as cracks or porosity on the surface of materials. Colors like red, yellow, or blue may be used in other forms of penetrant testing, but they do not provide the same level of visibility and contrast under UV light that green fluorescents do. Thus, green is particularly preferred in applications where increased sensitivity and visibility for defect identification are critical.