Abstract: A system and method is disclosed to automatically lift the curtains of the exit hood of a machine for the production of float flat glass by the floating process. A light beam emitter is provided for a light beam which strikes the surface of the glass ribbon, being formed, and is reflected by that surface. A light beam receptor receives the light beam reflected by the surface of the glass ribbon and provides a signal representative of the absence or deviation of the reflected light beam should there be a break in the glass ribbon. A controller receives the signal representative of the absence or deviation of the reflected light beam, and provides operating signals to the actuators of the i) curtain lifting mechanism, ii) reheating system, iii) glass edge follower mechanism and iv) alarm of the glass ribbon forming machine.