Glass and Color

Glasswork is an ancient craft dating back to Roman times and perhaps further back. It may be a testament to the skill of the earliest artisans that modern workers or artists use almost the same methods and tools. Such tools, including the glass, have become much more widely available in the modern age.

There are basically four methods to color these products. Each has its own distinctive advantages and disadvantages, and its own particular uses and time of appropriate application.

The first method is to use material that is already precolored. Such material acquires its color through the addition of metal oxide impurities. They are impurities in the sense that the metal atoms are dispersed throughout the material. When light passes through the otherwise transparent glass, the relatively uniform dispersal of impurities scatters the light, causing it reemit in different wavelengths.

The second method is to start with a small bar of colored vitreous substance, from which a small chunk is broken off. The small chunk is heated by placing at the tip of the blow pipe. The artisan blower may inflate the colored glass slightly, and then subsequently apply a clear coat over it. The blob is then marvered to smooth it out and shape it into a shape with cylindrical symmetry. The colored material remains on the interior of the clear glass.

The third method is to heat a piece of clear material on the end of the blow pipe, but then roll it in crushed substance. The crushed substance can be coarse like grains of sand or much finer like dust. The crushed glass is also known as frit. When the clear material is covered with frit, it's then brought back into the oven for heating which melts the frit into the clear substance, giving it color. The frit expands upon melting. Finer frit is harder to see when it melts into the clear product.

The fourth method is the overlay technique. A blower starts with a piece of clear material at the end of the blow pipe and melts it slightly. He then places a piece of solid, colored material over it, and then proceeds to force it down with metalwork tools.