When should excess penetrant be removed from the specimen?

The correct time to remove excess penetrant from the specimen is after the required penetrant dwell time has elapsed. This dwell time is crucial because it allows the penetrant enough time to seep into any surface defects or irregularities in the specimen. Removing it too early would mean that it hasn't had sufficient time to fill the flaws, potentially leading to inaccurate inspection results.

Furthermore, this process is part of a non-destructive testing technique used to identify flaws in materials, especially in welds and casting. Proper timing ensures that only the penetrant that is not inside any defects is removed, allowing for clearer indications of any flaws during the subsequent inspection step.

In contrast, removing penetrant immediately after application would not provide adequate time for the penetrant to enter the defects, and removing it while rinsing the surface could lead to insufficient cleaning and may wash away penetrant that has successfully entered any flaws. Applying penetrant prior to removing excess is not applicable, as the focus is on timing after application rather than prior actions.