A Review of the Current Practice of Glass Frosting
Glass frosting is the practice of making clear glass have a matte appearance by putting the glass in contact with a fluoride-based acid material. Glass is frosted to enhance its appearance, either over the entire surface, or in designs that can be applied using screen-printing, or with resist. Frosted glass is considered an attractive alternative to flint, or clear, glass, as it adds a different effect or aspect to glass products. Frosting is also well known for the cool, elegant, and attractive look it adds to glass containers, such as perfume, cosmetics, beer, wine, beverage, and liquor bottles. Frosting can also add attractive accents to flat glass, such as mirrors. The bottom line for decorators is that frosting increases the customer's interest in glass items: they like it, and they buy it!
Frosting is often confused with the various coloring techniques used to decorate glass. In both cases the result is the same, more attractive pieces of glass, but the techniques are different. Most other decorating techniques achieve their effects by covering or coating the glass. We call these "additive" decorating processes.
Frosting can be thought of as a subtractive decorating process, or one in which small quantities of the glass surface are removed, leaving behind a disrupted, rather than the original flat glass, surface. In the case of frosting, this effect is caused by the action of fluorides in acid solution. Professional frosting solutions have buffers which control and refine the reaction so that the glass surface, when viewed through a microscope has a regular and tight crystalline structure. These disruptions cause light that passes through or reflects off the glass to become diffused. It is the diffusion that makes the glass look frosty. Because frosting is a subtractive process, it is closer in nature to sandblasting. However, since the crystal structure left behind by the chemical reactions in frosting is very small, chemical frosting has a velvety feel and subtle sheen that sandblasting cannot duplicate.
An interesting analogy that can explain why frosted bottles look white and frosty even though it is still the same glass is the phenomenon of water in the atmosphere. Everyone knows that common water is clear; you can see right through it. So is glass! If you take water and break it up into thousands of very tiny droplets and disperse it in the atmosphere, you have clouds which can look white because the droplets of water diffuse light. This also illustrates a very important quality of frosted glass. Since it is not a coating, there is no foreign matter on the glass. Frosted glass is 100% pure glass and it is 100% recyclable. Having established that frosting is the result of chemical reactions that take place on the glass surface, we can describe the techniques used to frost glass.
The largest market for frosting is in the decorating of glass containers for cosmetic or liquor bottles. In this case, due to the volumes involved, a dipping process, which lends itself quite readily to automation, is used. Glass is simply dipped into a bath containing the frosting mixture. It remains in the bath for a period of time (15-45 seconds) and is allowed to drip for conservation purposes. Following the dripping phase, the glass is washed with water, either by dipping in a rinse bath, a spray rinse, or a combination of the two. After the rinse-off, the glass is dried, usually with heaters and blowers. The finished piece can either be passed along for further decorating, or packed and shipped to the customer (or filler).
The demand for frosted bottles is increasing! Packagers realize that frosting has point of purchase appeal that leads to increasing sales. In the beverage industry, the frosting of liquor bottles has been steady. We expect that wine, beer, and soft drink packagers will soon discover frosting in greater numbers. There is intense competition in this field, and frosting provides an upscale image that can set brands apart and create a certain image in the customer's mind. In the case of beer and wine coolers, the frosted look makes the beverage look cool and refreshing, and that is exactly the look the industry is thirsty for. To summarize, frosting gives glass a rich, elegant appearance and feel that arouses customer interest and increases sales.