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Decorative Concrete Stamping
Stamping Concrete 101: The Basics
by Susan Brimo-Cox
The primary purpose of release agents, which come in powder and liquid formulations, is to ensure your imprinting tools do not stick to the concrete. Liquid releases are clear and not all can accept color, so they are not used as frequently as powdered releases.
“Powder antique release is the most popular method of releasing the tools from the fresh concrete,” Thome reports. “It also offers you the option of adding one or multiple colors into your work.”
R. Michael Potts, owner of Ideal Construction Inc., says the release should go on very thin. “You are just looking to make a barrier between the concrete and the stamp. Don't put too much down, or your pattern will only be in the release powder and not in the concrete.”
Don't work too far ahead either. Cofoid recommends broadcasting only one or two rows ahead of stamping and cautions, “Never trowel release agent.”
When do you begin stamping? The concrete has to be firm enough to support the weight of the stamper and the tools, but plastic enough to accept the imprint. With rigid tools you can usually start sooner. Soft tools will require you to wait a bit longer, and then you'll likely need to use tamping tools. Some contractors say you can judge the concrete by pushing your finger into the slab. If it goes in about 1⁄4-inch, it should be ready to stamp.
Typically, you begin stamping where you began the pour. But there may be exceptions. For example, Branum says he prefers to start against a wall line or edge that is adjacent to any structures.
It's also important to know what parts of the pour are in the sun and shade. Concrete in the shade takes longer to firm up, while areas in the sun will stamp sooner.
Keeping grout lines crisp and eliminating squeeze lines is a matter of properly placing, aligning and lifting the tools. But Cofoid says not to worry if things aren't always perfect. “The stamping process is not perfect. Slight imperfections make it look more natural — stones are not perfect, bricks are not perfect.”
Plan the job out in advance. For example, if you have a crew of five (three finishers and two laborers), Thome says, “During the imprinting process you will need one person moving the imprinting tools, one person tamping or walking the tools in, one person on each side of the pour handing the tools to the tool setter and cleaning the tools as needed. The final person is probably the most important person — the detailer.”
Many experienced stampers recommend waiting until the next day to wash off excess release agent. Many caution against beginners using pressure washers, especially if you want some release agent to remain in the grout lines for additional color. (But be advised that release agent needs to be removed completely from the wear surface for a sealer to bond properly.)
“I like to first broom off the excess release, cut all my joints, and then wash it down with water from a hose,” Potts says.
Cofoid likes to rinse off release before cutting joints.
Like traditional concrete, stamped concrete needs control joints. In order to hide them you can try to line them up with grout lines in the pattern. With random stone patterns you might consider incorporating accent strips to accommodate the joints. If you use embossing skins for a continuous texture, joints usually are not distracting.
Proper curing time before applying a sealer is important. Follow the directions provided by the manufacturer.
Contractors and experts agree that practice, practice, practice is the way to go. Working alongside an expert is a great way to get comfortable with stamping, and having your crew practice in sand is a good way to familiarize them with a new pattern.
Carlton suggests that contractors take advantage of training seminars. “Paying for training by someone with 10 years-plus experience is money in the bank,” he says, “and creates a list of satisfied customers.”
Training satisfies several needs, Thome points out. “As someone interested in obtaining a better understanding of the business and how it can fit into their marketing program, the demo or introduction workshop might be enough. …To become familiar with the process and actually imprint a slab, the comprehensive workshop is the one to attend.”
Training classes are offered by manufacturers, independent schools and industry organizations. “Organizations such as the ASCC Decorative Concrete Council are an excellent training resource for contractors looking to improve their business and their skills,” Branum says.
One other piece of advice comes from Cofoid, who says to sell your work using actual samples. Form up 12-inch by 12-inch samples, but don't worry about them being perfect. “A perfect sample may give you trouble because the customer will expect perfect color. … [and] if you sell off photos you may have trouble because the color may not match up,” he says.
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