12/7/2023 0 Comments Streaked concrete texture seamlessIf water-based sealers are used, these lines can have a white milky haze to them, as the lap or roller line buildup did not allow the sealer to fully cure, trapping moisture. These lines become visible lap lines after the sealer has cured. In the case of push-and-pull applicators (such as mops or T-bars) the inertia or centrifugal aspect goes away, but downward pressure creating lines of sealer trailing off the sides leads to lap lines. If even more downward force is applied from the person pushing down on the roller, more liquid sealer will get pushed out to the sides of the roller, leading to larger amounts of sealer trailing off the edges. Gravity comes into play as it forces or pushes the roller down into the newly applied sealer. You need the roller spinning to get all the sealer up to the surface so it can come off the roller cover. Physical adhesion forces also play a part, but only on the surface of the roller. As the speed of the roller increases, the centrifugal force and inertia increase, depositing even more sealer onto the substrate. The inertia drives the material off the roller cover onto the substrate. Without getting into complex physics, let’s just say that the liquid sealer held in the nap of the roller has inertia as the roller spins across the surface. These forces are centrifugal force and the force of gravity. Photo courtesy of Chris SullivanĪs a roller runs across a surface, two forces are exerted on the liquid sealer as it comes off the roller cover. Rollers are recommended for lower-viscosity coatings, typically below 30 percent solids, while push-and-pull applicators are recommended for the higher-viscosity coatings with solids above 30 percent.įailing to maintain a wet edge resulted in clearly visible roller marks on this dyed concrete floor. Rollers roll and are a class of applicator unto themselves, while “push-and-pull” applicators such as T-bars, lamb’s wool and mops glide, with no rolling action, and are considered a separate type of applicator. Keep in mind that rollers are a different type of applicator from “push-and-pull” applicators, which leave lap lines. With all that in mind, let’s look at roller marks and lap lines, two of the most common problems with sealer application, and try to get a better understanding of why the marks occur, how to repair them, and how to avoid them on future jobs. Taking those factors into consideration, it’s actually pretty amazing how few problems do occur for the amount of decorative sealer applied each year. Also, if you are like most decorative concrete installers, your expertise is color and concrete, not sealers or coatings. We expect this “seamless” process to happen the same way day in and day out, even though each surface is different, each environment is different and each applicator is different. It’s as much art as it is science to get liquid sealer out of a can and lay it down in a thin and seamless film over a concrete surface. When you really think about it, sealing concrete falls more into the coatings industry than the concrete industry. Sealing concrete can be frustrating! Roller marks and their cousins, “lap lines,” are just two of those frustrating problems that can plague professional decorative installers.
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