glass of ten to twelve inches; if you’re blasting at a closer distance, lower the blasting pressure. “Before working on a project, always test your system and air pressure on scrap glass that you can pick up inexpensively at a dollar store or resale shop,” advises Chicago Brushmaster Ron Jelinek. Another variable is the angle of the nozzle to the plane of the glass. Generally you’ll want to hold the nozzle at a 90-degree angle or perpendicular to the surface of the glass. But if you’re adventurous and try glass carving, you can cut the glass at various angles to create special visual effects. Whether you’re etching or carving, Jelinek cautions to always pay attention to what you’re doing. “If you blast too close, too hard, or too long, you can actually burn or melt the stencil and ruin a piece of glass,” he says. The pressures required to etch glass can vary, depending on the type of glass you’re using. When sandblast-etching crystal (a softer glass), typical blast pressures range between 20- and 30-psi. Float glass (for glue chip projects) is harder and requires higher blast pressures. According to Roederer, frosting a large piece of glass can require as much as 80-psi. “Take your time when blasting so you frost the piece evenly,” she advises, “and carefully inspect the job when you’re finished working.” When engraving glass, Jelinek keeps blasting pressures as low as possible. Excessive blasting pressures can prematurely wear out the blast hose, nozzle, and other system components. Nothing lasts forever, and nozzles will eventually wear out. So regularly check the size of the orifice on the tip of the nozzle. “Eventually the threads on the coupler start to wear,” says Jelinek. “When that happens, air starts leaking through the threads. As the nozzle wears, the orifice enlarges. When the orifice becomes larger, the required volume of air increases, putting a greater burden on the compressor. And with the larger orifice, more abrasive abrades the stencil mask, which can cause the mask to break down faster. “As soon as [the nozzle] starts to fail, replace it,” says Jelinek. “If you don’t, the nozzle could shoot off the end of the blaster and shatter the glass.” signshop.com
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October 2013 // Sign Builder Illustrated
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