Why is it necessary to ensure a surface is free of debris before LPT?

Ensuring that a surface is free of debris before performing Liquid Penetrant Testing (LPT) is crucial to maximize defect detection capability. When a surface contains dirt, oil, grease, or other contaminants, these substances can mask or obscure defects, leading to false negatives where flaws go undetected. The whole premise of LPT is to enable penetrants to infiltrate discontinuities in the material, so any interference from debris directly hinders this process.

A clean surface allows the penetrant to effectively seep into cracks or voids, ensuring that any defects present can be revealed during the developer application phase. This enhances the reliability of the test results and supports the integrity of the inspected material or component, making it essential for accurate defect identification.