A method is disclosed for producing a hollow airfoil, specifically, a blade or vane for a gas turbine engine, which is formed with a complex interior for cooling purposes. Broadly, the method comprises the steps of molding a green ceramic core having outer surfaces generally contoured to produce the intended interior surfaces of the completed airfoil, heating the green ceramic core to a sufficient extent to produce a fired core, and operating on the fired core with a laser to modify the characteristics of the fired core. Use of the laser enables the formation of detailed features having a transverse dimension less than approximately 0.020 inches. Specific operations may include labeling, trimming, cutting, drilling either by punching or trepanning, etching or milling, and glazing or strengthening. In another embodiment of the invention, a layer is produced on the core surface having a very high surface energy to promote the flow of the casting alloy around the core within the mold.