Under the trade names of Dubl-Chek and Aqua-Chek, Sherwin Incorporated manufactures fluorescent penetrant and visible dye penetrant and related products used in the non-destructive testing of critical components in the aerospace and welding industries. Contact: Sherwin Inc., 5530 Borwick Ave., So. Gate, CA 90280, USA (562-831-6324; fax, 562-923-8370) ...