Developers enhance the visibility of penetrant indications, in this blog we explore the various forms and learn what makes them different.
How do developers work?
Developers enhance the visibility of penetrant indications by pulling penetrant from a surface open discontinuity and spreading the penetrant through the developer coating on the part surface. The penetrant indication may appear larger than its actual size as the penetrant spreads through the developer over time. Specifications state minimum and maximum development times to address the spread of penetrant through developer. The minimum development time should allow enough time for penetrant to be pulled from the surface open flaw and spread on the part surface for enhanced visibility. The maximum development time is in place to minimize excessive penetrant “bleed out” from an indication that could potentially obscure the indication.
Developers also increase the contrast between the penetrant and part background. With fluorescent penetrant inspection, the developer coating decreases glare from shiny part surfaces when viewed under UV light, highlighting penetrant indications and reducing eye fatigue of inspectors. With visible penetrants, developers provide a white background so that red dye penetrant indications are easy to identify.
Developers are available in various forms. Always review applicable specifications and company test procedures to identify approved developer options.