In the preceding chapters, we have discussed the functional and design concepts and techniques for optical thin film coatings and typical equipment which might be used in the realization of a physical coating on a substrate. We now address the additional factors of materials and processes needed to carry a design to its fruition. At the design stage, the index of refraction and dispersion are assumed values for the materials. This assumption is usually based on the best information available at the time of the design. The index includes the absorption (imaginary part of the index) which defines the spectral range over which the materials are usable. Guenther266 provides a useful review of the physical and chemical aspects of coatings. The durability of the materials in various environments such as abrasion, humidity, salt fog, solvents, etc., should be considered in the choice of materials before even starting a design with those materials. Durability in the space environment may also be of concern and has been reported by Blue and Roberts263. The availability of the equipment and processes to satisfactorily deposit a given material is usually a significant consideration also. The thrust of this chapter, therefore, is to share as much as practical of our experience with various materials and processes and to refer the reader to additional information in the areas discussed.