A method of exchanging a thin film coated tray for a clean tray is provided. The inventive ink formulations are based on multifunctional acrylate resins formed by the reaction of acrylate monomers and oligomers with \u03b2-keto esters, \u03b2-diketones, \u03b2-keto amides, andor other \u03b2-dicarbonyl compounds that can participate in Michael addition reactions. A clasp that houses a removable battery is fixed within the first discontinuity and a bead having an internally embedded LED is located within the second discontinuity. On operation of the magnetic field sensor, a current is temporarily applied to the excitation coil in order to bring the ferromagnetic core into a state of predetermined magnetization in which the magnetization of the ferromagnetic core produces no signal in the read-out sensor. The back surface 11b of the substrate 11 is polished until the substrate become a lamella having only a trace of the groove 22.