UV-Activated Sealer Cures in Seconds

Question:
I’ve heard about a new countertop sealer on the market that reacts with ultraviolet light. How does the sealer work and is it any good?

Answer:
The new sealer, called Counter-UV, manufactured by Kinloch and distributed by Surface 519, uses high-intensity ultraviolet (UV) light to cure the finish. It is formulated specifically for concrete countertops. While UV-curable finishes are common in the cabinet and flooring industries, a UV- curable sealer for concrete is a rarity. Historically, bonding issues have been the problem, but the manufacturer seems to have solved that with this product.

The finish itself is a specialized single-component, urethane-acrylic blend. It has no VOCs and offers excellent color enhancement, excellent stain resistance, and almost total acid resistance. Concrete Countertop Institute stain tests showed that only mustard left temporary discolorations in the sealer, and those could be easily and completely removed with household bleach. Very few sealers are completely resistant to mustard.

What makes this product so different from other high-performance sealers is how it cures. Most finishes, especially multicomponent products, can take hours to become tack-free and several days after that to reach full cure. Single-part finishes often merely need to dry out, so they become handleable faster. With the UV sealer, high-intensity, short-wavelength UV light initiates the cure. After exposure to the light for only a few seconds, the finish is ready for use. Thus you get the speed, convenience and ease of a single-part finish with the top-of-the-class performance offered by the best multipart finishes.

The UV sealer can be rolled on, sprayed on or wiped on. Rolling with a low nap (3/16- to 1/4-inch) lint-free roller is preferred, since the finish will flow out over time into a smooth film. Once applied, the finish does not cure and will not get hard, sticky or gummy until exposed to UV light. This is a great advantage because you can let the wet finish flow out or squeegee and back roll it repeatedly before curing.

You also have ability to adjust the sheen from high gloss to dead flat. If a glossy finish is not desired, you can sand the cured sealer to achieve whatever sheen level you’re after. But it’s best to use specialty sandpaper made for the solid-surface industry rather than ordinary woodworking sandpaper, which is not graded finely enough and can leave scratches in the finish. While these sanding discs are more expensive, they have very tightly controlled abrasive particle sizes that leave a uniform, scratch-free surface.

As with any finish, this one has its cons to go with the aforementioned pros. The finish will only cure with a specialized, high-intensity UV light. Sunlight, tanning lamps or fluorescent UV bulbs will not do the job. This UV light is expensive—about the same price as a large, high-quality concrete mixer. Because of this, it is cost prohibitive to try a sample of the finish, because without the UV light, the finish will not cure.

A white GFRC desk sealed with Counter-UV.

Unless you want a high-gloss finish, the only way to get a lower sheen is to sand it. And because it’s a tough, scratch-resistant finish, sanding takes time. Curved surfaces and intricate molded edging can be a challenge, too, and will require effort and skill to achieve high-quality results.
While some of these disadvantages seem significant, the system as a whole saves you the time of waiting for a finish to cure. It also is one of the easiest finishes on the market to repair, since repairs blend in well.