D-350 along with KO-17 Penetrant and KO-19 Remover comprise Sherwin Inc’s Hi-Temp Penetrant System, which works at temperatures above which ordinary penetrants are ineffective. D-350 developer consists of refined white particles suspended in isopropyl alcohol to give enhanced sensitivity for locating tight, incipient flaws. By solvent and capillary action, it pulls flaw-entrapped penetrant to part surfaces for display against a white background. It is not recommended for use at temperatures lower than 175F. At lower temperatures, D-350 dries more slowly. Also, the particles are more adhering at lower temperatures and require greater effort to remove upon completion of the inspection process. Removing D-350 requires wiping with water-dampened toweling.