The best temperature to apply a concrete sealer is 55-85 degrees Fahrenheit, however, the air temperature is not the only factor to consider when applying a concrete sealer. Other factors include the temperature of the concrete and the time of the day.
Air Temperature: In a perfect world, concrete sealers should be applied when the outside temperatures is within 55-85 degrees Fahrenheit. While this temperature range isn’t always achievable depending on the time of year and where you are located, there are some safe and manageable work-arounds. Temperature will manipulate how fast or slow a product cures, and how well it is able to cure. If you apply a product outside of the temperature guidelines in the morning or mid-day, it may result in discoloration, bubbling, or even coating failure. In the event that you are applying a concrete sealer above 85 degrees we recommend applying later in the afternoon between 6-8 pm. During 6-8 pm, the sun is setting or has set, the air and surface temperatures are reducing, minimizing the potential for solvent pop, bubbling and blushing. It is always suggested to contact the manufacturer of the product if you have questions, or if you feel that you can’t stay within temperature guidelines. In most cases, sealers can be applied outside of suggested temperature guidelines as long as other guidelines, such as the temperature of the concrete and time of the day, are followed. In no case however will a sealer be able to properly bond and cure when the temperature is below freezing. Water based products will freeze, and solvent based products will take days to fully cure, if at all. Most of the flexibility with temperature is on the higher end of the guidelines.
Time of Day: This is very important. You do not want to apply a concrete sealer first thing in the morning, and you do not want to apply a concrete sealer in the middle of the day. If you apply a concrete sealer in the early morning, there is a 99% chance that subsurface moisture is present within the pores. Water will cause most sealers and coatings to fail, resulting in discoloration (blushing) and delamination. The concrete may look dry, but the pores of the concrete could be filled with water below the surface. The middle of the day is also a terrible time to apply a concrete sealer because as the concrete is exposed to extreme UV rays, causing the surface to heat up. As the temperature rises, hot concrete, and hot air temperatures, can cause trapped air and gasses to expand producing bubble in the coating. Other effects of applying mid-day are; premature evaporation of the carrying agents (water or solvents), and result in sealer failure, or delamination. The best time of the day to apply a concrete sealer is in the late afternoon or evening when the sun is setting, air temperatures are declining, and the concrete surface has had time to cool from exposure to UV rays.
Temperature of the Concrete: As mentioned above, this is a very important factor, especially when applying an acrylic sealer. If you apply an acrylic sealer in the middle of the day when the concrete is hot, it can cause solvent pop. Tiny bubbles will appear over the entire surface of the coating. In severe cases, the acrylic sealer will delaminate. Issues can also arise with penetrating sealers if the concrete causes the water or solvent to evaporate before the sealer has had time to fully absorb into the substrate. The best time of the day to apply a concrete sealer is in the late afternoon or evening when the air temperatures are declining, the sun is fading, and the concrete surface has had time to cool from exposure to UV rays. If the concrete is hot to touch, you want to wait until it no longer feels hot to apply.
Top Issues That Arise From Applying Concrete Sealers Outside of Temperature Guidelines
Penetrating Sealers: Penetrating sealers typically have a little more flexibility when it comes to application, but issues can still arise:
- If applied when it is too hot, or when air and surface temperatures are increasing, the carrying agent (water or solvent) can evaporate before the sealer has had a chance to penetrate and react, leaving you with unreacted material on the surface, or discoloration.
- If applied when it is too cold, water based sealers can freeze, and solvent based sealers can take days to cure, if they are able to cure at all.
- If applied to a wet surface, or a surface with moisture below the surface, penetrating sealers can fail, or cause discoloration.
- If applied when it is too hot, or when air and surface temperatures are increasing, the carrying agent (water or solvent) can evaporate before the sealer has had a chance to bond, leaving you with unreacted material on the surface. Further, solvent based sealers can heat up, trapping gasses below the surface, causing the formation of surface bubbles. Other issues include discoloration, delamination, failure, white spots or hazing, and inconsistencies in appearance.
- If applied when it is too cold, water based acrylic sealers can freeze, and solvent based sealers can take days to cure, if they are able to cure at all. Both cases typically result in coating failure, amongst other issues.
- If applied to a wet surface, or a surface with moisture below the surface, acrylic sealers can fail, or cause discoloration. Most acrylic will develop white spots or a white haze that will need to either be repaired or removed.
Please note, it is always best to check with the sealer manufacturer to see what they suggest for application windows and application instructions.