Iridized Sheet Glass
Wonder how iridized glass is made? Basically, we apply a metal coating to the surface of the sheet glass by a process known as spray pyrolysis. As metal salts are applied to the very hot glass surface they burn, or pyrolyse, and the metal ions bond to the glass surface.
When the resulting coating approaches 1 wavelength of light in thickness (about 1/3 micron), colors appear. These coatings are known as 'thick' coatings, and have no transmitted color. They are less intense and shiny than dichroic coatings, which are much thinner, and are known as 'thin layer' coatings.
Color variations from gold and blue, to pink, purple and green swirling throughout Rainbow irids result from minor variations in thickness of the coating. Specific colors such as Gold or Silver irids are thinner and require even more specific thicknesses. Tin based irid coatings add substantial strength and resistance to chipping to the glass surface.
The iridescence of ancient glasses occurred over long periods of time, as buried glass was exposed to metal salts in the earth, and metal bonded to the glass surfaces in appropriate thicknesses. Tiffany was the first to deliberately reproduce this affect for decorative reasons, using primary Tin and Iron.
How to use irids in stained glass work? Iridized glass can by used in myriad ways to add rich color, and glittery highlights to glass. It is especially vivid on textured surfaces, such as our Granite, or Herringbone Granite Ripple textures.
Start with anything in nature that has a natural iridescence...peacock feathers, beetles, fish scales to name a few, and use irid glass to represent it.
Even when you are working in stained glass, pre-firing iridized sheet glass in a kiln, particularly under a clear layer (or lense) can add additional lustre and depth. Or, try placing the irid side down against the shelf surface or mold wall for a solid, durable, and extra colorful surface.