Avoiding Streaks When Applying Water-Based Sealers

Question:
How do I prevent streaking when wiping on a water-based sealer?

Answer:
The wipe-on technique is commonly used to apply water-based sealers. Typically it involves using a microfiber cloth to apply a very thin, even film of sealer. Done right, it’s a fast and easy way to lay down a beautiful finish.

However, water-based finishes can be tricky to apply because they get sticky quickly as the finish loses water. Achieving a smooth, streak-free finish is possible only if the wet sealer has time to flow out before it dries. If the wet film of sealer isn’t thick enough, or if the finish dries too soon, the wiping marks won’t disappear and streaks result.

Water loss can happen in two ways: through evaporation and through absorption by the concrete. If the finish is applied very thin, then it flash dries before it flows out. Applying a thicker wet film helps, plus the added material flows out more readily than a very thin film. A hot, dry environment accelerates evaporation, so a light spray of water on the sealer as it’s being spread will also help it stay fluid. Be careful not to overapply the water. Just give the sealer a quick spritz, not a thorough soaking.

Dry concrete often sucks water out of the sealer, dehydrating it. Prewetting the concrete with water helps eliminate this tendency. I soak the concrete with water for several minutes, then wipe up excess water with a microfiber cloth. This leaves the surface slightly damp and won’t draw moisture out of the finish.

The final trick to achieving a flawless wipe-on finish is keeping the cloth properly saturated with sealer during the final wipe-down. If you wring out the cloth too much, you’ll remove too much sealer from the concrete surface. The cloth should be very wet with sealer but not dripping. The sealer in the “wake” of the cloth should flow out very quickly, leaving a smooth film. If the concrete looks barely wet with sealer, too much is being removed.

The key to achieving streak-free results when applying any sealer is practice, whether you are using a quick-and-easy wipe-on sealer or a complex, multipart, spray-applied system. I see too many people trying to apply sealers to their clients’ countertops before they have adequately practiced the technique. Practice is the only thing that makes perfect!