When dye penetrant inspection indications are unclear, what is the most likely cause?

In dye penetrant inspection, the clarity of indications is crucial for identifying surface defects. When the part is not thoroughly washed before the application of the developer, residual contaminants such as grease, dirt, or previous coatings can interfere with the penetration of the dye. This leads to unclear or insufficient indications as the dye may not properly seep into potential cracks or flaws, making it difficult to detect them during inspection.

Thorough cleaning of the part is essential to ensure that the surface is free from any materials that can obstruct the dye's ability to highlight defects. If the surface isn’t adequately cleaned, the presence of these contaminants can mask the true state of the material's integrity, leading to misleading or unclear indications during the inspection process. Proper washing is therefore a critical step in ensuring the effectiveness of dye penetrant inspection.