The problem is applying sealers to decorative concrete in extreme
temperatures. Both air and surface temperatureplay a role, but surface
temperature is typically more critical. After application, sealers undergo a
chemical reaction that causes them to cure and form a film. Temperature
plays a critical role. The best temperature range for applying sealers is 50
to 90 degrees

F. That 40-degree window is really not very big, especially when you’re working outside. This is why monitoring weather conditions
and looking at a thermometer should be mandatory before every sealer ap-application. Here’s what can happen if temperatures are too low or too high.

Low temperature – Every sealer has a minimum film forming temperature
(MFT). Most manufacturers specify 50 F minimum temperature to apply
sealers. If the temperature is at or slightly below the MFT, the chemistry of
the sealer is affected, the reaction slows down, and you get partial to no
film development. Bottom line: The sealer is weak and will not hold up very
long. If the temperature is really cold, film development stops altogether
and all you are left with is a white powder on the surface after the (solvent
or water) evaporates.

High temperature – Temperature is a catalyst. As the temperature in-
creases, so does the reactivity of the sealer. Increased reactivity de-
creases the working time, or pot life, of the sealer. The faster the reactivity,
the less time the sealer has to wet out the surface, de-gas, and form its
film. This makes it critical to get the sealer down on the concrete quickly
and efficiently. As temperature increases, the ability to roll out sealers be-
comes more difficult. It is recommended to spray on solvent-based seal-
ers, especially in warm conditions. A common indication that the tempera-
ture is to high is the formation of fine “spider webs” or “cotton candy”
strings coming off the roller or spray tip. This occurs when higher tempera-
tures cause the solvent to flash before the resin (plastic) in the sealer can
form its film. The pressure from the sprayer or friction from the roller pulls
the soft plastic into long, thin strands.

Another common issue caused by the higher temperatures is the formation
of bubbles or blisters in the sealer. They occur when the solvent flashes to
fast, trapping gas and air in the sealer. With today’s tightening VOC re-
requirements more fast-flashing solvents are being used, which makes the
window of application even smaller. Apply the sealer during the cooler time
of the day, typically morning and evenings.

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Filed under: Acid Stained Concrete Floors • Decorative Concrete Flooring • Epoxy Garage Floor

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