In water-washable penetrant testing, when is the wet developer applied relative to penetrant removal?

In water-washable penetrant testing, when is the wet developer applied relative to penetrant removal?

• A. After removal of the penetrant
• B. Before application of penetrant
• C. During dwell time
• D. After washing

Answer: (A)

Wet developer is applied after the penetrant has been removed. In water-washable penetrant testing, the penetrant is allowed to dwell in any surface-breaking flaws, then the surface penetrant is washed away with water. What remains is penetrant inside the flaws. Applying the wet developer at this point lets it interact with that residual penetrant, drawing it to the surface to create a clear, visible indication. If the developer were applied before removal, the wash could carry it away or disturb the penetrant, reducing sensitivity and producing weaker or misleading indications.

Wet developer is applied after the penetrant has been removed. In water-washable penetrant testing, the penetrant is allowed to dwell in any surface-breaking flaws, then the surface penetrant is washed away with water. What remains is penetrant inside the flaws. Applying the wet developer at this point lets it interact with that residual penetrant, drawing it to the surface to create a clear, visible indication. If the developer were applied before removal, the wash could carry it away or disturb the penetrant, reducing sensitivity and producing weaker or misleading indications.