In a water-washable liquid penetrant test, when is the wet developer applied?

In a water-washable liquid penetrant test, the wet developer is applied after the removal of the penetrant. This sequence is important because the developer acts to draw the penetrant out of any discontinuities that may exist in the test material. By applying the developer following the removal of the penetrant, it creates a contrast that enhances the visibility of any potential defects or flaws.

The removal of the penetrant is a critical step because it actually cleans the surface, but some penetrant may remain in cracks or voids. The developer, when applied, will absorb any remaining dye and provide a clearer signal regarding the presence of defects. This process establishes a contrast that makes any indications much more visible for inspection by the technician.

In this context, it's essential to recognize that applying the developer too early, such as before or immediately after the penetrant, would not yield the most accurate results, as it could interfere with the effectiveness of the developer in highlighting defects. The timing of the developer application is, therefore, crucial for the overall integrity and accuracy of the testing process.