Fluorescent Inspection Penetrant FL50-18 (12 oz can Aerosol [carton of 12])Flaw Finder FL50-18 is a biodegradable, water washable penetrant. It also meets the QPL requirements for solvent removability and post emulsifiability. FL-50 has lower dragout than most penetrants and has proven to be superior for use on such difficult materials as beryllium. Method Hydrostatic Leak Testing requires that a component be completely filled with a liquid such as water. Pressure is slowly applied to the liquid until the required pressure is reached. this pressure is held for the required time at which point the component is inspected visually to locate leaks.