Stamping patterns and textures in concrete started in the 1950s and still is considered to be the bread-and-butter of the decorative industry. Starting with cast aluminum stamps, the industry transitioned to plastic stamps in the late 1970s and then added closed-top stamps that imprinted both textures and patterns by 1980. Initially, small texture mats added texturing for closed-top stamping applications in small areas that platform stamps couldn't reach, but it didn't take long to develop large texture mats. Using them, contractors could imprint texture without patterns, providing a new look and, at the same time, making installation easier to perform.
The manufacturing of stamps and texture mats now is considered a mature decorative industry, so there are not big changes regarding the resins used to make them or to their construction.
What makes a good stamp?
The hardness or softness of the resin used to make platform tools is a matter of personal taste. Harder resins make it easier to stamp softer concrete while softer resins perform better on harder concrete. Each contractor has a preference, and tool manufacturers make decisions about what they think most contractors want. But the rigidity of a tool is only one of the criteria for a good stamp.
The Shore Rating is the number used to indicate the hardness of a resin. Shore A, with a hardness range of 65 to 90, is most used by manufacturers. Tyler Irwin, national sales manager for Proline Concrete Tools, Oceanside, Calif., says the Shore hardness they use for their tools is 95, allowing them to make the tools thinner. “Using stamps with this Shore hardness means there can be more difficulty when concrete gets too stiff,” he says. “But our stamps make it possible to start stamping earlier, providing more time for the stamping process.”
Jerry Garceau, vice president of Butterfield Color, Aurora, Ill., says they use resins with a Shore hardness of 80—a middle-of-the-road resin that supports a person's weight while achieving consistent imprints. This is the direction L.M. Scofield Co., Douglasville, Ga., and Increte Systems Inc., Odessa, Fla., have taken as well. Art Pinto, the production manager for Solomon Colors Inc., Springfield, Ill., says they use a softer resin to fill the bottom half of the mold (where the pattern and texture are) and then switch to a harder resin for the top half, getting some of the benefits of both. He adds that Solomon also is working on a green resin, using recycled material to make stamps.
Scott Thome, director of product services for L.M. Scofield, says a good stamp is dimensionally stable, regardless of ambient temperature changes, which depend on the type of resin used to make the stamp and controlling temperature-humidity in the room where casting takes place. Generally, urethane resins generate a lot of heat and set quickly, making them the most susceptible to dimensional change. Stamps that are dimensionally stable also group tightly together during the stamping process.
It's all about the pattern
First and foremost, the pattern's look is the most important consideration for both clients and contractors. Pinto says they have selected a range of patterns that were cast from old European paving stones because they wanted an authentic look. Garceau adds that lower profile patterns and textures help contractors to achieve more even impressions from the start of a session to the end because less concrete is displaced. Good patterns have tapered pattern lines to facilitate a clean release.
Bernard McGuire, Increte Systems' marketing manager, stresses that good pattern systems mask the repeat of pattern units. Two ways to accomplish this are to not use a distinctive unit in the creation of a mold, and to create several interchangeable stamps with different unit arrangements. Using stone stamps that rotate also introduces randomness.
New and custom patterns
Even during slow economic times, stamp manufacturers produce new patterns and custom stamps for clients. Manufacturers who have been in this business for many years can have as many as 1000 different pattern molds in their inventories.
Last year, Butterfield introduced a circular cobblestone pattern. Increte currently is marketing two new slate patterns and a cobblestone stamp. McGuire also notes that wood-grain patterns are becoming popular again, especially for restaurant and commercial applications. Proline has introduced a tool for stamping circular patterns, which can be used for any radius in the circle. They have also introduced travertine textures, a slate pattern, and a stone stamp.
Custom stamps for specific job applications make it easy for manufacturers to introduce a new pattern because the client pays the molding fee. But they also can be so specific that no one else would want to use them. Thome says they received a request from a Dubai contractor to produce a pattern that looked like a dried up mud puddle with small crack patterns—a common look in Dubai. To do it, they mixed batches of mud and spread it out on the ground to dry, letting nature take its course, and then molded the result.
Choosing a stamp or texture mat
As a contractor, you probably already have a relationship with a manufacturer that you trust and make pattern choices based on customer needs. However, it's wise to think about the other marks of a quality stamp and how it performs in the field. In the end, you will own it for a long time.