When using a dry developer, when should the drying operation be performed?

Using a dry developer in liquid penetrant testing is critical for revealing surface defects. The drying operation should be performed immediately after the excess penetrant has been removed. This timing is essential because the developer must work on the surface while there is still a thin film of penetrant present.

By applying the developer right after removing the excess penetrant, you allow it to absorb any remaining surface penetrant and promote the formation of a clear indication of any flaws. This step ensures that the developer can effectively draw the penetrant out of the defects, leading to more visible and interpretable indications during the inspection.

Performing the drying operation after cleaning (which involves removing excess penetrant) would diminish the effectiveness of the developer, as it could not properly absorb the penetrant from any defects. Therefore, doing it before any cleaning would also interfere with the inspection process. Lastly, waiting until the penetrant is dry before applying the developer would not be effective, as the timing for the chemical action would be compromised. Hence, the optimal action is to apply the developer immediately after the penetrant has been wiped away.