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In the brick industry, large amounts of raw fuel are often poured into the kiln to create a color effect known as “flashing.” For those involved in the manufacture of brick, flashing is a necessary evil. It is costly, difficult to control, and can cause unwanted stack emissions. If it could be eliminated from the process, nearly everyone involved in firing would likely stop using the technique immediately. So why is it such a frequent practice?
The look of brick is its best selling point, and the market will continue to demand the “flashed” look in the finished product. How it is produced is of little consequence to the customers. And flashing has been the only way to achieve that look—until now.
Simulated FlashingA new coating (developed by Southern Color & Chemical Co.) is available that duplicates not only the colors, but also the patterns and effects of flashing. This method of coloring allows for control and versatility that would be difficult, if not impossible, to achieve by normal coating methods. The colors are applied using a spray system (supplied by Multi-Spray & Pneumatics, Ltd.) that gives the manufacturer precise control of where the colors are applied. Several colors can be sprayed intermittently to get a varied look.
The spray system uses air to atomize the fluid through a spray gun that has no needle. The fluid is turned on and off using an air-controlled diaphragm. The on/off air is controlled with a programmable logic controller (PLC) that is programmed by the operator. Diaphragm pumps deliver color slurries through fluid regulators so that the pressure can be precisely controlled. This control enables consistent, repeatable color application.
On a typical setup, each color goes to two individually controlled guns. By changing the orifice size in the guns, the user can vary the amount of color applied, which adds to the variation in appearance and keeps the color application from looking mechanical. The most commonly installed system sprays three colors through six guns that are housed in a booth. The booth can be rolled into place, and then rolled away when not in use. The colors are pumped from 26-gallon poly tanks that are constantly stirred to ensure color consistency. Pressure for the atomizing air is controlled by regulators in the control panel, which also contains the PLC.
The color is typically applied to the brick column as it exits the extruder and is dry before it reaches the setting stage—no smearing or bleed-through has been observed on any of the plant trials. The color can also be sprayed on wet molded or dry brick without any adverse effects in durability or performance. Samples from all three application methods have been acid-washed (a standard coating-durability test) without any ill effects.
The equipment for such a system is not cheap—a typical system spraying three colors runs about $60,000, and the coating itself costs around $2 per 1,000 brick. But by reducing fuel usage and increasing efficiency and repeatability, such a system can usually pay for itself in a short period of time. Additionally, eliminating flashing can greatly reduce stack emissions, making environmental compliance more easily attainable.
Color DuplicationThe coatings have been developed through trial and error in a lab and in various brick plants, and are achieved by blending pigments and minerals, both natural and synthetic. So far, nearly every color commonly seen on flashed brick has been duplicated using these coatings, including gun metal blue, shades of black and brown, and hues in gold to orange. Customized formulas can be made to match the color variations found from plant to plant, and there are few limitations with regard to how many colors can be achieved.
No longer are brick producers limited by their materials and kiln as to what colors they can produce—the only limit is their own imagination.