3M Innovative Properties Company has been granted a patent for a cyanoacrylate-based adhesive composition comprised of a cyanoacrylate monomer; and a bleachable dye comprised of Michler's hydrol cation, or derivatized Michler's hydrol cation, paired with a non-nucleophilic anion that provides a stable color to the cyanoacrylate-based adhesive.
Source:
http://www.coatingsworld.com/issues/0713/view_patents/3m-patents-color-change-cyanoacrylate-adhesives/
