Unfortunately, the reduction flashing process—in which the kiln is fired under reducing conditions to obtain the flashed effect—is wrought with challenges and is subject to a great deal of variability. The composition of the raw material (particularly the iron content); the flashing and reoxidation time and temperature; the type of fuel; the maturing temperature; the area of the kiln in which the flashing occurs; the airflow inside the kiln; and the method, temperature and atmosphere of cooling following reduction all influence the color and effect of the flashed brick. As a result, flashing is difficult to control and repeat from batch to batch. Additionally, the color or effect can only be achieved on the outside of the brick package, and the excess fuel required to achieve the reducing atmosphere can lead to higher manufacturing costs for producers of flashed products.
General Shale Brick, headquartered in Johnson City, Tenn., was convinced that there had to be a better way. Several years ago, the company began experimenting with a system of colored sand that could be applied to the brick body before firing to achieve a flashed effect. While these efforts were successful in several plants, the sand did not work with every product line.
Recently, however, the company began using a new type of applied flash, in the form of an engobe supplied by Prince Manufacturing Co. of Quincy, Ill. Unlike earlier generations of engobe flashes, the new system has been proven to successfully reproduce just about any reduction flashed color or effect—without the drawbacks associated with reduction flashing.
“Flashed brick comprise the majority of products throughout General Shale,” said Bob Keyes, manager of automation and technology. “The ability to produce the flashed look using engobes instead of a reducing atmosphere in our kilns could have a big impact on our product quality and our bottom line.”
“We’ve had a number of problems with reduction coloring our brick,” said Keyes. “Fuels have increased in price over the last several years, so the cost of flashing has escalated. Additionally, because only the outside of the package is flashed, we can’t get a blend of the flashed colors throughout the package. By necessity, we are moving toward automatically packaging our product, but without a good blend of colors on the kiln car, the packaging machine has to be very elaborate and very sophisticated.
“Reduction flashing also creates quality problems—the increased heat required for reduction flashing creates significant size variations and cold water absorption differences within the load. Additionally, the low iron content of our material, as well as the use of coal-fired, high-draft kilns at Corbin and other facilities, makes it difficult to achieve the dark flash we require,” Keyes added.
When Prince approached General Shale with the new engobes in the fall of 2000, the company didn’t hesitate. “We’d been working fairly closely with Prince for the last three or four years and had been using their engobes and colors on a number of our products. When this new system for applied flashes came along, we were eager to try it,” said Bob O’Quinn, director of research.
However, the company still needed some new equipment to apply the flashes with the right effect. “Often the biggest challenge for any company who’s trying to apply an applied flash engobe is to do it in such a way that it’s a reproducible, intermittent pattern of light and dark shades. It isn’t just a continuous spray,” said Jon Attridge, R&D manager with Prince.
Rather than purchase an application system from a supplier, General Shale decided to custom-design its own proprietary system using some of its existing spray equipment, as well as some additional off-the-shelf components.
“We felt like we had enough experience in the area of sprayed-on engobes, and we knew exactly what we wanted. We knew we could come up with a good system that would give us the technique we needed to apply the flash. Additionally, we already had a mechanical system in place that we thought would lend itself to doing exactly what we wanted to do,” said Keyes. “As far as the equipment is concerned, almost everything we use is pretty much off the shelf. The key is how you put the pieces together, and the technique you use to apply the spray-on flash.”
According to Keyes, one of the biggest challenges the plant faced in transitioning to the applied flashes was getting the employees to think differently about flashing. “We’ve been reduction flashing our brick for the past 50 years, so we had some trouble convincing people that we could produce a brick that was virtually identical to the reduction flashing with an applied engobe out of the millroom on the greenware. Once the column moves out and dries a little bit, it’s often hard to tell that you’ve put anything on it,” he said. “When we ran the initial tests, folks looked at it and just kind of smiled; you knew what they were thinking. But after the brick came through the kiln and we laid the panels up, everyone could see that the applied flashes would work, and that they would be better and easier for the plant. It didn’t take long to get everyone on board.”
“Our lab has also seen a reduction in color complaints coming from the plant, especially the stripes in the wall caused by irregular distribution of the brick in the package,” added O’Quinn.
Color stability and reproducibility have also improved. “With reduction flashing, the flashed effect would change at different times of day and in different seasons due to changes in airflows and atmospheric effects inside the kiln. The worst times were the transition periods in the spring and fall. Applied flashing, on the other hand, provides a consistent color day in and day out, and we don’t have to worry about having our flashes set up exactly right every time a particular brick comes through the kiln,” Keyes said. “As a result, our throughput of A-grade brick has improved.”
All of these benefits are expected to have a positive impact on the plant’s bottom line. “We’re currently doing a study on the measurable benefits of the applied flashes. While the results of the study aren’t yet complete, we are seeing in our preliminary figures that there are savings in going from the reduction flash to the applied flash, both in fuel and increased product quality,” O’Quinn said.
“We’re also seeing some savings in inventory,” said Keyes. “With the reduction flashes, we had to make sure that all of the brick shipped to a sizeable job were out of the same run, so that there weren’t any color variations in the wall. This required us to keep a large inventory for those jobs—what we call ‘job-lotting.’ With the applied flashes, we no longer have to job-lot brick because we don’t have to worry about color variations.”
General Shale is also looking at using applied flashes in its Johnson City, Tenn., and Roanoke, Va., plants, and others are likely to follow in the future.
“As General Shale looks at implementing the applied flashes at our other plants, we’re doing it mainly for two reasons,” said Keyes. “First, the consistency—the ability to produce the same color range over and over and over—is a tremendous benefit. The second reason is the cost consideration—the savings in fuel and inventory, as well as an increase in product quality, will help us improve our bottom line.”
As additional improvements are made in the applied flash technology, it is likely that the industry as a whole will be able to completely phase out the difficult process of reduction flashing in the future.
“We’re trying to make it as easy as possible for plants to use applied flashes,” said Tom Henderson, director of business development at Prince. “We are in the process of working with a company called Autojet Systems to develop some spraying equipment for use in the brick industry. But while spray application is a very good and economic way to apply these types of applied flashes, it is not the only way. A pump-and-roll system in combination with an air knife is another alternative, and we’re also working on a dry-applied version of the applied flash that could be used with slight alterations to the sand applicators that are currently used throughout the industry.
“The benefits of applied flashes are clear. But for plants that do not already use liquid spray equipment, moving into the applied flashing technology in a quick manner can be difficult. As these other technologies are introduced, using applied flashes will become easier and more cost-effective,” Henderson said.
For more information about General Shale Brick, contact the company at P.O. Box 3547, Johnson City, TN 37602; (800) 414-4661; or visit http://www.generalshale.com.