While it is always best to follow a manufacturer's suggestions for when and how to apply a concrete sealer, we have found the best time to apply most concrete sealers is in the late afternoon or early evening. During the late afternoon, any moisture present from condensation or morning dew will have evaporated off during the day. Also, both the surface temperature and air temperature are declining, creating a more favorable environment for concrete sealers to properly absorb and bond to the substrate. Applying concrete sealers in the late afternoon helps to avoid such issues as; solvent bubbles, premature evaporation, discoloration, and blushing.
Here are a few other frequently asked questions about sealer application:
1. Why isn't is suggested to apply a concrete sealer in the morning? Most people assume morning is the best time to apply a concrete sealer, but that isn't always the case. In many parts of the country, dew or condensation is present on the concrete and in the pores. If you apply penetrating water repellent sealer or an acrylic sealer to wet concrete, many issues can arise such as improper penetration, discoloration and blushing. In addition to potential moisture, rising temperatures are also a concern. As an example: in the morning, the air and surface temperature may rise from 60 degrees to 90 degrees which may cause gasses or air trapped within a coating to expand producing unwanted bubbles.
2. Why isn't is suggested to apply a concrete sealer around noon? The sun starts to rapidly heat up the surface around 10am and continues to keep it hot until around 4-5pm. If you apply a penetrating sealer to hot concrete, the solvents can off-gas or evaporate too quickly preventing the sealer from properly penetrating and reacting within the substrate If an acrylic sealer is applied to hot concrete in directly sunlight, the solvents and trapped air will expand too quickly, resulting in solvent bubbles on the surface.
3. After I clean the concrete, can I apply the sealer once the surface looks dry? No, you can't. If the surface gets wet you need to allow the substrate 24-48 hours to dry, ensuring all moisture above and below the surface has fully evaporated.
4. How many coats should I apply? Two coats are always suggested because the first coat of any concrete sealer is usually absorbed into the concrete at different rates leaving the substrate unevenly sealed. A second coat will ensure proper even coverage.
Still have questions? Call a member of technical support at 866-306-0246.