Iridescence in Tiffany Glass: The Alchemy of Favrile

Iridescence is the optical phenomenon where a surface appears to change color depending on the viewing angle and lighting. For Louis Comfort Tiffany, this effect was the definitive trademark of his Favrile glass, patented in 1894. Unlike earlier forms of art glass, this rainbow effect was not painted onto the surface, but was an inherent part of the glass itself.

The Inspiration: Roman Ruins and Weathering

Tiffany's obsession with iridescence began after a trip to Europe in 1875. He became fascinated by the iridescent weathering of ancient Roman and Syrian glass that had been buried for centuries. The chemical reaction between the glass and the minerals in the soil created a luster he sought to replicate in his modern studio in Corona, Queens.

The Alchemical Process: Metal and Vapors

To create this effect artificially, Tiffany transformed his glass furnaces into a laboratory for alchemy. The process was extremely complex:

• Metal Oxides: While the glass was molten (at approximately 2400°F), oxides were added such as gold chloride (for red tones), cobalt oxide (for blue), and silver nitrate.
• Chemical Reduction: The hot glass was exposed to specific metal vapors in an oxygen-deprived environment. This caused the metal particles to migrate to the surface, forming a microscopically thin, reflective layer.
• Embedding: Because this occurred while the glass was still molten or glowing hot, the luster literally became part of the molecular structure of the Favrile glass.

Painting with Light

This iridescence gave Tiffany's objects a vibrancy reminiscent of organic material. It allowed his artisans to faithfully mimic the shimmer of water or the iridescent wings of the Dragonfly Lamp. The glass acts like the skin of a soap bubble: it captures white light and breaks it open into a dancing spectrum, making a static object seem to breathe with every movement of the viewer.

Deepen your knowledge:

Discover how these iridescent qualities were applied in complex mosaics in our article on Tiffany-style Glass Mosaics or learn more about the technical architect behind this glass, Arthur J. Nash.