How does surface finish affect the results of liquid penetrant testing?

A rough surface finish can obscure defect indications because it introduces irregularities that may trap penetrant materials, making it difficult for them to flow into any surface-breaking defects. If the penetrant cannot adequately reach the defects, it will lead to incomplete or missed indications during the testing process. The intricate textures of a rough surface can also scatter light, complicating the visual detection of indications under ultraviolet or visible light, which further hinders the examiner's ability to identify flaws.

In contrast, while a smooth surface indeed enhances the ability of the penetrant to penetrate, it does not obscure defect indications like a rough surface would. Likewise, a polished surface may reduce the need for developer due to its uniformity, but this does not have a direct impact on the detection of defects. An uneven surface may create more opportunities for detection but can also introduce challenges, such as areas where penetrant can pool unnecessarily, leading to false indications or masking actual defects. Thus, the impact of surface finish on testing outcomes must be carefully considered for accurate assessments.