The technology involved in the production of lustered and iridized art glass by Louis C. Tiffany has been investigated by analysis of fragments and replications, and found to be far more complex than had been believed. Glass compositions, surface reduction processes, and thin-film coatings are discussed within an historical perspective of the late nineteenth-century fashion for Art Nouveau glass and the contemporary understanding of glass technology. One vase is described in detail with regard to its composition, microstructure, and manufacture, as an example of technology focused to produce objects with striking visual impact.