Cleaning of extremely sensitive optical surfaces

Most of the optical surfaces are sensitive; the cleaning should be done with great cares and using well characterized technique and equipment. In this paper we are reporting about cleaning of some of the most critical optical surfaces, surfaces which are generally known as not allowing any cleaning. The first section reports about the cleaning of the silver coating on an echelle grating. Silver becomes oxidized, or tarnished, from exposure to sulphates in the air. With time this can lead to dramatic loss of the efficiency of the grating. The second section reports about the cleaning of a CCD chip which has been contaminated with grease. A special "contactless" cleaning procedure has been developed and used successfully on real components. In both cases the full procedure is described and a set of measurements document the results and shows how the original performance have been recovered.