Last month, we introduced you to stampable overlays: what they are; how products differ and why that matters; how to mix and apply the overlay; and how to tint liquid release agents, which are used more often than dry release agents for stamping applications and, unlike dry agents, are usually clear.
Now comes the tricky part.
Successful stamping is a combination of careful planning, good timing, and sufficient tools and labor. Plan and practice to avoid heartbreak when you’re placing stamping tool to overlay.
The Overlay’s Ready for Stamping When…
Knowing when the freshly placed overlay is at the right consistency to take the imprint is one of stamping’s trickiest aspects. Some applicators gently press the surface with a finger; if material doesn’t stick, the time is right. Others visually inspect the surface. During finishing, you’ll usually see some bleeding of water or polymer that settles on the surface; start stamping when bleed water dissipates and the surface sheen dulls.
Ideally, there will be slight resistance when you tamp the stamping mat to make the impression. Practice on samples at your shop until you become comfortable with the best time to start.
Keep in mind that the proper timing is often a function of pattern depth and project size. Deeper textures may require stamping earlier than light textures, especially if the placement is large. The goal is to obtain a uniform stamp impression over the entire surface before the overlay sets
To make sure you can do that, determine which direction to run the stamping tools before placing the overlay. If you wait until the overlay is down, you’ll get behind and the material will start to set. With some patterns, such as running-bond brick or cobblestone, running the pattern square is important to maintain alignment and prevent the illusion the pattern is shrinking or enlarging when viewed from different angles. Sometimes you can avoid problems with squareness by running the pattern on a diagonal.
When learning how to place a new stamp pattern, it’s always a good idea to practice beforehand on a layer of wet, compacted sand. If you mess up, re-level and compact the sand and start again.
Finishing Before the Overlay Sets
Stamping in the proper sequence is also important. In general, stamp in the same sequence you placed and finished the overlay because material that goes down first will reach proper plasticity first. Having a worker pretexture 6 inches to 12 inches of the perimeter edges with a seamless texturing skin helps ensure sufficient texture and full color from the release agent is worked into edges. In addition, include a flexible stamp, sometimes called a “floppy,” in your set of stamping tools. Unlike a more-rigid pattern stamp, the highly pliable floppy bends up against walls and steps.
Have enough mats to cover the area so you can keep the pattern aligned and move across the surface quickly. Also have enough tools to span the overlay’s widest area plus at least two more tools to start the second row. You also need enough workers – a minimum of three to four people – on the job to keep the process moving.
If you start stamping at the proper time, a slight layer of mortar will squeeze up between mats. Smooth it out with a detail roller or a rounded tool used for smoothing grout in brick joints. Devote one worker to detailing as the stamp mats are lifted and work progresses. If some areas are inadvertently missed, the detailer can walk back out to fix these spots using texturing skins as stepping stones (as long as the skins match the stamp pattern), assuming the material has reached sufficient set to support the worker’s weight. Alternatively, someone can do the detailing the next day by using a chisel to carefully break out excess mortar.
As you can see, stamping can be a complicated process. However, with proper training and some hands-on experience, you’ll become proficient in no time.