Some manufacturers chose using electrical corona discharge, flame treatment, cold gas plasma, and ultraviolet irradiation as pre-treatment methods to achieve bonding with a wider range of adhesives. Each of these methods are application-specific and possesses unique advantages and potential limitations. The basic mechanism that happens in this process is a combination of both chemical and physical reaction. http://www.xysiliconeink.com/silicone-ink/embossing-silicone/