Masking shall be copper plate per AMS2418, bronze plate per AMS2429. Alternative methods, such as masking paste, may be used if acceptable to the cognizant engineering organization. Copper plate shall be fine-grained and non-porous, not less than 0.001 inch (0.025 mm) in thickness. Bronze plate shall be not less than 0.0005 inch (0.0127 mm) thick.