Cause of White Streaks in an Overlay

White streaks of sealer indicate overapplication with a roller.

Question:
I used an 18%-solids water-based acrylic sealer on an interior stained microtopping. Certain areas of the floor remained white and hazy, as can be seen in the picture. Why did this happen, and how do I fix it?

Answer:
When dealing with sealer-related problems, the trigger mechanism often revolves around one or more of the following factors: moisture, temperature, surface contamination, and application method. In this case, the long, thin streaks of white indicate overapplication of the sealer with a roller. If the roller is overloaded with sealer, it tends to drag large amounts across the surface in streaks and ribbons. These thicker streaks of sealer skin over on the top surface, preventing the sealer from fully curing. Instead of turning clear, the sealer remains white and milky in appearance. Another factor at play is the surface texture of the overlay. If the surface has differences in elevation, sealer tends to puddle in the valleys. It will also collect in cracks and joints. These areas are more susceptible to this white hazing or milkiness.

With water-based sealers, fixing this situation can be as easy as applying a thin solvent bath or as involved as stripping the entire area, depending on the sealer product used. A simple solvent (xylene, acetone, or methyl ethyl ketone) wiped over the surface can loosen the sealer, allowing the underlying material to cure and turn clear. If this method doesn’t work, or destroys the sealer, you’ll need to use a chemical stripper to remove the affected areas. (Be sure to test the stripper on a small section first to determine the effect.) Once the entire area is stripped and cleaned, reapply the sealer, taking care not to overload the roller.