The use of a developer is required by most penetrant inspection testing specifications. The developer draws the penetrant from the flaw and creates a uniform surface on which to view the penetrant indication. D-78B is used with fluorescent penetrants (Type 1) and visible penetrants (Type 2)as a form “c” developer. This form of developer is generally applied by immersion dip, flow on, or gentle airless spray, prior to the drying process. A uniform film will form during the drying.