“If it was easy, everyone would be doing it, and you wouldn’t have an opportunity.”
—Junethea Crystal Centeno
Glass has been fascinating mankind for more than 5,000 years. It can reflect light or transmit it. It can be an invisible shield or a colorful adornment. It can be as strong as steel or as brittle as a potato chip. What other such useful material can also be such an iconic art device? So why isn’t everyone creating graphics with it?
Glass can be used to create many specialty items to increase sales.
Well, glass is also known to be difficult to work with. Its super-hard, non-porous surface repels paints of all descriptions. And then there’s the breakage, and the weight. But it can be worth it all in the end. Remember, if it was easy anybody could do it—and would.
There are, however, many ways to get an image onto glass—all with different advantages and disadvantages—many of which can be used in combination with each other for myriad choices.
This mechanical process uses either lasers or high-speed rotary tools that are either hand operated or computer driven. The result is a lightly recessed surface on the glass that is more opaque in appearance than the un-engraved portions. The bits for the rotary tools are usually diamond chip coated in order to attack the super hard glass surface. With the manual process the results are only as good as the practitioner behind the tool. Some people can create amazing works of art, while others look somewhat amateur.
Computers, on the other hand, produce reliable, if somewhat boring, results. Either of these processes are only useful on small jobs like recognition plaques or giveaways and are seldom suitable for large projects.
In a commercial sign shop application, sandblasting is a more useful method of engraving. Sandblasting can dig much deeper into the glass and covers large surface areas evenly and easily. The patterns to be engraved are cut out of a sheet of adhesive-backed resist (using either computer or hand cutting) and the resist applied to the glass. The open areas are then blasted with fine particles of sand, silicon carbide or aluminum oxide. All of these are noxious powders so the process always takes place in sealed rooms or containment boxes using protective equipment and breathing gear.
Sandblasting can create a substantial recess in the surface, which can be easily filled with color. There are many types of inks that will work on glass for short periods of time, but only resin-based inks that require baking will be relatively permanent. The colors, however, are gorgeous, rich translucent tones that make the graphics glow like the sun.
Etching is a treatment for glass that just roughens up the surface, turning it from transparent to translucent in the areas that are etched. The process can be done with caustic creams or acids. The caustic approach uses resist masks much like sandblasting.
This sign was sandblasted and filled with translucent color. The close-up view (top)reveals the texture that was worked into the glass.
Caustic creams containing fluorides are rubbed into the open areas of the resist and then washed off, leaving a lightly etched surface behind. For etching with liquid hydrofluoric acid, the non-etched areas are coated with a resist that repels the acid. This is usually done using a screen-printing technique. The acid is washed over the glass and then washed off. Please note—this is as very dangerous process and must be done with proper safety equipment!
Images can also be baked onto the glass. Special printing paper for fused glass is available from glass wholesale suppliers. The print is applied like a water appliqué decal and sandwiched between two layers of glass, then fired in a kiln at 1,350 degrees. This provides an extremely durable outdoor-grade product with amazing translucence and high-resolution imaging.
Direct Digital Imaging
UV-curable direct digital inkjet inks can be used to print onto glass, but only after the surface of the glass has been treated or pre-coated. The easiest way is to spray the glass with a special coating that allows the ink to stick to the glass.
A more durable method is to use a plasma treatment method. Plasma is an alternate state of matter that is neither gas, liquid nor solid. When plasma contacts the glass surface its energy is transferred to the surface. This creates a higher level of molecular surface motion, allowing superior ink adhesion. Printing has to happen relatively quickly after plasma treatment.
Ceramic enamels are printed onto the glass using electrically heated screens. The inks become liquid when heated. When the liquid inks contact the cold glass surface, the mixture instantly solidifies. This is then fired in a kiln to fuse the enamel to the glass. The glass is then slowly cooled for several hours to bring it to room temperature. This is a very expensive, but very durable process.
But of course we can’t forget the old standby—decals. Any shop can print decals onto a clear adhesive film and apply them to glass. Installation onto the glass is a bit tricky and requires some practice, but the final result is a beautiful, durable and inexpensive way to decorate glass, no new equipment required!
In addition, several vinyl manufacturers offer products that give the appearance of etched or frosted glass. This is an inexpensive solution to glass etching, and the effect can be very convincing.