How long should excess developer be left on the surface before inspection?

The best practice for leaving excess developer on the surface before inspection is typically between 10 to 30 minutes. This timeframe allows enough time for the developer to absorb any remaining penetrant that may still be present in the surface flaws, enhancing the visibility of indications during inspection. If the inspection occurs too quickly after applying the developer, there may not be sufficient contrast or clarity in the findings because some penetrant could still be trapped within the surface, leading to false readings. Conversely, leaving the developer on for too long may result in over-drying or could allow contaminants to jeopardize the inspection process. Thus, adhering to the 10 to 30 minutes timeframe ensures optimal media interaction and more reliable detection of defects in the materials being tested.