What is the primary function of a developer in liquid penetrant testing?

In liquid penetrant testing, the primary function of a developer is to draw penetrant out of defects. This process involves applying a developer to the surface of the test material after the penetrant has been allowed to dwell and seep into any surface flaws or cracks. The developer acts by absorbing the penetrant that has been absorbed into the defects, creating a visible indication of the flaw on the surface.

This method enhances the visibility of the defects, making them easier to identify during inspection. By drawing the penetrant out, the developer helps to contrast the defect against the surface, thus revealing flaws that might otherwise go unnoticed. This step is critical for ensuring the accuracy of the testing, as it allows for a clear assessment of the integrity of the material being evaluated.

In relation to the other options, while making the light absorbent, changing the color of the penetrant, and providing illumination during inspection could be factors in ensuring effective testing and visibility, none of these options directly address the key role of the developer in extracting the penetrant from defects to highlight them for visual inspection.