Description of Calcedonia Glass

People often ask me to describe the colors of Calcedonia that I make. I find it hard to describe  because of all the layers and striations of color that vary so much from sculpture to sculpture, even coming from the same pot of melted glass! That is why I have named the Calcedonia that I melt, Mystery Opal. It speaks to the mysterious way the colors develop and react while heating and cooling it, blowing and shaping it, never knowing exactly what it will look like until the work comes out of the annealing oven the next day.

I had started working with a formula of Calcedonia glass before I met Dino Rosin, the great Italian glass Master, without knowing much of the history of this type of glass. During my visit with him, he gave me his book, ‘L’Arte Dei Rosin’. In it, he describes this mysteriously beautiful and ancient glass: “Calcedonia, as its name implies, is a type of glass that echoes the multicolored striations of the zoned agate. Unlike many types of glass that imitate semiprecious stones, it is not created by mixing together two or more colors of glass. The colors, shades and markings of the mysterious Calcedonia result from a chemical process intrinsic to each batch of glass; a reaction based on the effect of the metal silver on the other minerals and substances used to make glass. Each pot of Calcedonia requires silver nitrate to achieve the subtle beauty characteristic of this glass. Even today, the production of Calcedonia is an expensive and unpredictable process, more akin to alchemy than chemistry. While the action of silver on the other materials generally results in a blend of colors – browns, greens, and a hint of blue – the exact shades and degree of striation cannot be controlled and vary. Each piece is a unique work of art combining an ancient technical process with the best of modern craftsmanship.” Only the best from the great Master himself!

I wanted to share this, so that you may get a little bit more understanding of this wonderful glass color and why it intrigues me so. Coming up next, my experience with Calcedonia glass...


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