A silver mirror process is described which can provide mirrors with excellent environmental durability. The stresses which can develop in dielectric protective or enhancement layers are discussed, and an estimate of the coating stress induced by an active component is obtained. It is speculated that as state-of-the-art coatings approach bulk optical properties, the mechanical properties, especially the yield strength, may also approach bulk values; if this happens, the possibility exists that coatings will craze on a typical active surface.
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