Acrylic vs. Penetrating Sealers

There are many different types of concrete sealers available, but when talking about concrete flatwork in New England, the two most commonly used are film forming acrylic sealers and penetrating sealers. Although they both seal concrete, they do so in COMPLETELY different ways

.Acrylic sealers work by forming a protective film atop the concrete. The film protects the concrete in much the same way that a raincoat protects its wearer. The sealer simply covers the concrete surface with a water resistant barrier.

**It is a myth that you can make acrylic sealer penetrate deeper into the concrete by diluting it with xylene.**

The solid acrylic particles are a certain size and they simply cannot be made smaller by adding more liquid. Trying to make acrylic sealer penetrate deeper is like trying to make gravel flow through a window screen by adding water to it. The liquid will flow through, but the solid particles will remain atop the screen. All that is accomplished by diluting sealer is that the solid particles are spread further apart and become less effective as a barrier.

Acrylic sealers come in both water based and solvent based formulations. In both cases, particles of acrylic solids are suspended in a liquid carrier (either water or a solvent such as xylene or acetone). The wet sealer is applied to the slab, the liquid carrier dries or evaporates, and the solid particles are left on the surface to form a film.

Solvent based sealers emit very strong vapors, have an offensive odor, and can be hazardous to your health. For this reason, great care should be taken if using them indoors. Especially in basements and other enclosed spaces, even a spark from a pilot light can cause the fumes to ignite and explode. In addition, the solvents used can cause health problems. Water based sealers on the other hand, do not emit hazardous fumes. They have a mild smell similar to interior house paint and are not flammable.

Although water based acrylics and solvent based acrylics both coat the surface with an acrylic film, they have their differences. Solvent based acrylics darken the surface and are typically glossier than waterbased acrylics. Customers who desire a darker, shinier finish on their concrete and want marked contrast between the base color and antiquing color should usually go with a solvent based acrylic. Those who want more subdued colors or a matte finish while still retaining some gloss should opt for a water based acrylic sealer.

Unlike film forming sealers, penetrating sealers are not coatings. They usually contain silane, siloxane, or silicates that do not form a film on the slab’s surface, but instead chemically react with the concrete to coat the pores with a hydrophobic substance. They seal from within by creating an atmosphere that simply won’t allow water to enter. It’s similar to filling a cup with molten wax, then trying to add water once the wax has hardened. Since the space is already occupied with a waterproof substance, there’s nowhere for the water to get in.

Slabs treated with penetrating sealers do not significantly change in appearance. In fact, other than water beading up on the surface, you’d never even know they had been applied. This makes them a good choice for resealing plain brushed concrete without darkening or shining it, or creating a more natural appearance on stamped & decorative concrete.

To get the best of both worlds, there are sealers such as ChemMasters Silencure which combines film-forming acrylics with penetrating silane. This sealer, available in both water based and solvent based formulations, cures and protects concrete by not only creating a film atop the concrete, but also by filling the pores within.