SEALER SERIES Part 6: When Temperature + Moisture = Condensation

Water that condensed on a stained concrete floor by a cold doorway
caused the sealer to white out in that area.

We have covered how moisture (Part 3) and temperature (Part 4) can each affect sealer performance. But what happens when both come into play? Here’s a mini lesson in meteorology to explain the problems that can occur when the two conspire.

The air that surrounds us always contains water vapor, but the amount of water can vary. Humidity is the measure of how much water is in the air at any given time. We would not have to worry about this water vapor if it just remained trapped in the air as a gas. But it doesn’t because temperature fluctuations convert that water vapor into a liquid. If temperatures rise and enough water is in the air, instability is created and rain can fall. As temperatures fall, condensation can occur in the form of dew. For example, on cool summer nights, you’ll often see dew-covered cars, grass, and other surfaces once morning comes around. The dew point is the temperature at which water comes out of the air and becomes a liquid.

What does all this have to do with sealers and decorative concrete? A lot, if not taken into consideration before sealing. As humidity increases and temperature decreases, water will condense on cool surfaces. Since concrete is a sponge, it will absorb the condensation. The problem is that the slab surface won’t look wet, but hiding just beneath it can be lots of collected water. If a sealer is then applied to the surface, the trapped water can cause the sealer to white out or not adhere properly. Outdoors, this problem is more common during transition seasons (spring and fall) as nights get colder but humidity is still high during warm days. Indoors, this problem is prevalent in the winter near walls and doors where floor temperatures are colder.