Commissioned Stained Glass
Tiffany patented Favrile glass in 1892. Favrile glass, as used in the hummingbirds, often has a distinctive characteristic that is common in some glass from Classical antiquity: it possesses a superficial iridescence. This iridescence causes the surface to shimmer, but also causes a degree of opacity. This iridescent effect of the glass was obtained by mixing different colors of glass together while hot.
According to Tiffany:
"Favrile glass is distinguished by brilliant or deeply toned colors, usually iridescent like the wings of certain American butterflies, the necks of pigeons and peacocks, the wing covers of various beetles."