_ Is powdered glass the consistency of sand which has been applied to prepared copper using funnels and sifters according to the artist's vision. It's then fired in a kiln at temperatures ranging from 1350 to 1500 degrees Fahrenheit, fusing the glass onto the copper.

The technique has examples still existing from antiquity, which tells you it is very durable.  It is glass fired onto copper and will hold up fine outside as yard art, depending on the medium on which it is mounted .  The pieces mounted on wood for instance, would need to be kept under cover or inside or the wood will deteriorate.