Summer Sealer Basics

Question:
When the weather is hot, what should I watch out for when sealing exterior decorative concrete to prevent problems?

Answer:
Most one-part sealers used to beautify and protect decorative concrete work on the principle of evaporative curing. The liquid portion of the sealer evaporates, leaving the solid plastic resin to form a hard, clear film on the surface. As the surface temperature increases, the rate of evaporation increases. This is especially true when dealing with solvent-based sealers. The typical recommended surface temperature range for sealing is 50 F to 90 F. Consult the technical guidelines for the specific sealer you use, since some of the VOC-exempt solvents being used these days evaporate VERY fast.

Even though surface temperature is the key factor, don’t forget to consider air temperature. If the air temperature is in the 90s, the sealer will flash cure, causing spider webbing or bubbles, no matter what the surface temperature is. Common sense would dictate that during the hot months, avoid sealing during the heat of the day.