U.S. Air Force Senior Airman Joshua Thomas, 33rd Aircraft Maintenance Squadron nondestructive inspection technician, tests the spray of a liquid penetrant, one of the many methods used to reveal surface discontinuities of aircraft equipment May 5, 2021, at Eglin Air Force Base, Florida. Fluorescent penetrants contain a dye or several dyes that fluoresce when exposed to black light. (U.S. Air Force photo by Airman Colleen Coulthard)