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 bond to the substrate and cure. 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. If you apply a solvent based acrylic sealer and the acrylic sealer heats up before curing, solvent bubbles will form. If you apply a water based acrylic sealer the acrylic sealer heats up before curing, the water from the sealer can evaporate too quickly, leaving you with delamination issues.
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 the water can evaporate too quickly, preventing the sealer from properly penetrating and reacting within the substrate. If a solvent-based 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. With water-based acrylics, the water can evaporate too quickly, leaving you with a delaminated coating.
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, unless otherwise specified by the manufacture, 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 even coverage and appearance.
Still have questions? Call a member of technical support at 866-306-0246.