Monday, July 19, 2010

Why do I have blisters in my sealer?

Ask a Pro

Q. -  We've used a solvent base sealer product two seasons now and both times were done in proper weather conditions and both times bubbled (blistered). Could this be because surface of patio is hotter then outside temp (although we applied it one year at 6am and the other time at 8pm) or is it because we're putting it on too thick? This condition is after first or second coat, didn't make a difference.
Hello Bill
A. -  When solvent base sealers blister during application, it's because the temperature of the surface it is being applied to and/or the air temperature is too hot. Strong hot direct sunlight will also cause it. What happens is the Xylene or whatever solvent the sealer has as a base, tries to flash off too fast and it blows bubbles in the sealer as it exits.
   A couple points: Rolling a fresh coat of sealer on should re-liquefy the existing sealer, allowing both coats to settle back out, and effectively remove the bubbles completely. That is if it's done when it's not too hot, otherwise they would just come back. You are correct that the concrete temp was likely hotter than the air temp, especially if it had direct sunlight. Perhaps you should try to seal early in the day, after it has had the night to cool, and preferably in the shade, and in a temperature range of the 70's F, and no higher than the low 80's F if possible. If you are continuing to get bubbles and blisters then you may need to seal during a cooler time of year, or switch over to a water base sealer.
   Finally, if you do start getting blisters during sealing, then you can use leaf blowers to blow across the surface of the sealer after you seal it - yet before it dries, which will pop the blisters and allow the sealer to settle back out, and dry down without them.