An optical coating on a transparent substrate is provided with a temporary layer of carbon as protection during manufacturing against scratches and corrosive environments. When the optical coating and/or substrate are tempered in an atmosphere reactive to carbon, such as air, the layer of carbon is removed...http://www.google.es/patents/US20050260419?utm_source=gb-gplus-sharePatente US20050260419 - Protective layers for optical coatings
