What is the best choice of developer for use on a very smooth surface when using a fluorescent penetrant?

The best choice of developer for use on a very smooth surface when applying a fluorescent penetrant is the wet developer. Wet developers are formulated to enhance the visibility of surface-breaking flaws by providing an optimal environment for the penetrant to be absorbed and drawn out of defects.

On very smooth surfaces, where surface irregularities are minimal, a wet developer can create a thin layer that allows for even distribution and optimal fluorescence. This ensures that any indications formed from penetrant trapped in defects are clearly visible under UV light.

In contrast, other types of developers, such as powder, dust, or dry developers, may not adhere properly to smooth surfaces or may produce uneven coverage, which can lead to difficulties in detecting flaws or inconsistencies in the indications. The application of wet developer also promotes better contrast under UV light conditions, making it the preferred choice for achieving reliable and accurate results in liquid penetrant testing on smooth finishes.