A qualitative pilot test used to determine whether water-wet solids (for example, barite) exist in an oil-base mud. An oil mud is put into a clean, round, glass quart jar filled about 1/3 full. The mud is stirred on a commercial-grade mixer or blender for 15 minutes. The mud is poured out and the jar, drained and examined. Solids strongly adhering to the glass are indicative of the presence of water-wet solids in the mud. The test has been correlated with inside plugging of drillpipe, which occurs when an oil mud becomes under-treated with oil-wetting agent. The electrical stability test cam be used to evaluate wettability and emulsion quality along with evidence of free water in high-pressure, high-temperature filtrate.