Achieving a Smooth Finish When Applying Sealer

Question:
I’m having trouble with my sealer. The finish doesn’t look good. Can you help?

Answer:
Choosing the right sealer is a very important decision when it comes to making a high-quality concrete countertop. Protecting concrete is a balancing act between preserving the look and feel of bare concrete and providing long-term protection. But the performance of the sealer isn’t the only thing that matters. How that finish is applied has a significant effect on the look and feel of the countertop.

Finishes for concrete countertops fall into one of two main categories: penetrating treatments or film-building coatings. With coatings, the application method is often an important factor not only in the appearance but also the performance of the coating. If the material is not applied evenly or sufficiently, then the resulting film cannot protect the concrete in the way it’s expected to. Here are two tips that will help you apply coatings successfully:

1. Always apply coatings to the thickness the manufacturer recommends.
   Coatings must form a continuous film to create a nonporous barrier between stains and the concrete the coating is protecting. Generally, thicker films offer more protection than thinner films, but protection also depends on coating chemistry and whether a thick film is necessary in the first place.
   
   One common criticism of coatings is that they look like plastic and obscure the natural feel of bare concrete. This is not always the case. Many coatings can protect concrete when applied at a thickness of only 4 mils, or about the thickness of a sheet of copy paper. This is thin enough that the concrete does not look like it has been coated. Don’t, however, go to the extreme and thin the coating too much. The coating can become porous on a microscopic level, leaving the concrete unprotected and vulnerable to staining and etching.




2. Practice, practice, practice!
   Practice is essential to mastering coating application. The best sealer is useless if not applied smoothly and consistently, no matter how stain-resistant the finish. Poorly applied coatings will leave streaks, drips, runs, sags or other physical blemishes that spoil the look of the countertop, leaving the finished product looking amateurish and plastic-like.
   
   Achieving a smooth, blemish-free film depends on the skill of the person applying the finish, the quality of the tools used, environmental conditions and the properties of the wet coating. Follow the manufacturer’s application instructions, and practice them on samples before attempting them on a client’s project. Most coatings are applied with a sprayer, roller or rag. Brushing is not often used. Ultimately the application method should put down an even, wet film of the desired thickness and give the coating a chance to flow out before it dries. If a finish dries out before it flows, roller marks and holidays left from application will remain in the finish.