DENTON, TEXAS - It was a rite of passage that many North Texans of a certain age remember well. Schoolchildren who took a field trip of Acme’s Denton Plant were given a small brick paperweight at tour’s end. But those souvenirs were made not at the big brick plant, but at a very special facility co-located with it: the Acme Brick Technical Center.
If kilns are the beating heart of Acme Brick Company’s brick making operations, then the Technical Center is its brains.
Known as the “Denton Lab,” the center bristles with testing equipment of various kinds. But it also includes clay mixers, extruders, and several brick kilns – essentially an entire brick plant in miniature – all under the direction of manager Mat Tramel. The center’s training room hosts training seminars for architects as well for mining and kiln operators. It’s also the home of Acme’s exploration department, where new potential sources for raw materials are evaluated.
I Brick Your Milkshake
Early in the brick manufacturing process, mined mineral deposits are ground into fine particles. To assure product consistence, plants send clay samples to the lab for particle size equivalent (PSE) analysis. Technicians mix the ground clay with water as you would a milkshake, then take measurements. PSE determines how much clay, sand, and silt are present in the sample, which in turn assures that it meets that particular plant’s standards.
In a separate testing facility, finished brick are evaluated by four key measures;
Initial Rate of (Water) Absorption: Technicians weigh a finished brick, set it in a pan filled with an inch of water for one minute, and then weigh it again to determine how much water the brick absorbed.
Compressive Strength: Basically this involves placing a finished brick in a heady-duty hydraulic press – and then turning up the pressure until the brick fails.
Freeze/Thaw: This test also measures brick’s ability to stand up to extreme conditions, in this case weather. Freezers and kilns are used to rapidly cycle a brick through wide temperature swings.
Efflorescence: This also involves setting brick in a pan of water, only for a week instead of a minute – then placing them in an oven. If the body of the brick has a high sulfate content, those minerals will leach out of the brick and produce white (or even greenish) deposits on the brick’s surface. The purpose of the test is to assure that any efflorescence that might develop during installation can be removed with careful cleaning when the job is complete.
Always Exploring, by Land and Air
From evaluating sources of raw material to prototyping colors and blends, the Technical Center is where Acme’s manufacturing future takes shape. These efforts are led by Jim Krueger, a longtime Acme associate who is manager of Research and Production Services.
Clay may seem like an inexhaustible resource, but it can be a challenge to find new clay deposits that are a) suitable for brick manufacture; and b) in sufficient quantity to support decades of mining. Acme’s Exploration Department meets this twofold challenge every day.
New raw materials can come either from existing sources (either farther out or deeper) or from entirely new deposits. In both cases, the evaluation process begins by taking long, cylindrical “core samples” at regular intervals in the area under study, to show the layers of clay in the deposit area.
Back at the lab, the samples are evaluated not only for suitability but also for desired color. “Each section of a core might produce a different color body,” Mat Tramel said. “If the plant has a target of orange, we may be able to use the full core sample area material. But if it comes back too light, and we’re looking to make red brick, then we would look somewhere else – hence the term ‘exploration.’”
The Exploration offices contain surveying maps annotated with results; historical samples; maps of current mining operations; and a comprehensive archive of survey data, satellite images, topographical maps, and geological maps with elevation changes.
The department even has its own drone to aid in surveying.
The lab is also a center of new-product development because it is configured for small-batch production rather than high volumes.
Many factors influence the appearance of a finished brick: the composition of the clay itself, firing temperature, additives, and surface coatings. And the lab can test them all.
So the quest for the next Acme bestseller generally begins with the shipment of a large bag of brick clay from a plant to the lab’s receiving area.
This clay gets graded, placed in large metal bowls (“hats”), then sent to a dryer. The next day, the dried clay is ground and passed through screens, to a fineness consistent with its plant’s specifications.
Next, the ground clay goes to a mixer, where water is added to form large balls of brick “mud” – again, according to the plant’s native spec. These are fed into an extruder to make long strips, which are cut by hand to make 3-foot bars - ten bars in all. “The first two,” Mat said, “go for firing, bars three and four for dry testing, and two to the plant so that they can run their own tests and compare their results to ours.
“The rest are spares in case of accidents, power outages, etc.”
Before firing, bars are sent to one of four dryers, one of which is computer controlled and pre-programmed with up to 100 temperature profiles (“heat curves”) that simulate conditions at each plant.
Finally, to compare different firing temperatures on a brick sample, a bar of clay goes from to the dryer to a specialized kiln called a gradient furnace. This furnace can maintain up to eight temperature zones, ranging from 1,800 to 2,200 degrees, concurrently. It’s a more efficient process than testing temperatures one sample at a time.
What’s the Occasion?
The lab also excels in another kind of small-batch production: the miniature, felt-backed Acme Brick paperweight. Given to plant visitors, handed out at trade shows, or left with valued customers, this souvenir has graced countless thousands of desks over the decades.
Commemorative units that mark an Acme milestone, such as a plant’s anniversary, will receive a custom stamp. Others receive a generic imprint. In both cases, making paperweights involves not just impeccable craftsmanship but also real artistry. “For stamping, we need to design thoughtfully,” Mat said, “with larger lines, fewer curves to hold the detail.”
Paperweights are made the same way as test brick, he explained, but with a little more care. “We might sand the edges down to make sure they’re not sharp, and ee might dry the bar a bit before stamping so the brick won’t crumble,” he said.
Most Acme paperweights are made from Denton clay blended to produce a color called Ranger Red. Occasionally, however, the lab will use brick clay from the Perla Plants, in central Arkansas, that produce brick with a white body.
So the next time you see an Acme Brick project, whether it’s the paperweight on your desk, the building you work in, or even your own home, know that thanks to the Denton Lab, you’re looking at one very smart building material.