Multicomponent oxide glasses can be produced not only by melting methods but also by hydrolysis and condensation of alkoxide complexes with several metals. This requires temperatures only up to the transformation range of the glass in question, usually 500600°C. The process does not pass through the molten phase. It is possible to obtain glasses or polycrystalline substances, depending on the composition. The method is particularly suitable for the production of thin, transparent multicomponent oxide layers of almost any composition on substrates. Some of these layers provide protection against climatic attack or against oxidation.

The Principal material used in optics is glass. Plastics can only gain acceptance in optics if they have properties not encountered with glass or if a desired article can be produced more rationally from a plastic. An example of the first case is provided by UV light guides consisting of a quartz glass core surrounded by a plastic cladding; there is no glass with a sufficiently low refractive index. Examples of the second case are viewfinder optics for camerás and lenses for sunglasses and industrial safety spectacles.

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