October, 2006

50°F (10°C) And Rising


Water Based Latex coatings systems depend upon the evaporation of water to develop a dried and cured coating film.  There are several factors that have a significant impact on the ability of the coating to cure properly.

The major factors are:

  • Air Temperature – temperature must be sufficient to evaporate the water
  • Surface Temperature – a cold surface (below 50°F) will retard the rate of water evaporation
  • Relative Humidity – higher humidity slows the rate of drying
  • Sunlight/Shade – The sun can warm a surface to the proper temperatures.  Absence of sun can affect surface temperatures by more than 10°F.
  • Air Movement – This is needed to change the relative humidity at the surface/atmosphere contact point.
  • Coating/Film Thickness – Thicker coatings take significantly longer to dry.
  • Surface Color – Darker surfaces dry more quickly

The specification for The Plexipave System states that the temperature shall be 50°F and rising for application.

This phrase can be interpreted.  It is the position of California Products Corporation that application of our water based coatings system should take place only when the air and surface temperature and other conditions must be conducive to complete drying of the coating within the same day of application.

This would indicate that if rain is imminent or the air and surface temperature falls below 50°F before the coating has an opportunity to fully dry within the same day, then application should not be attempted.

It is well accepted that at the minimum application temperature the drying time of a waterbased coating is greatly extended.  This means that the proper film formation of the coating can be effected by falling air and surface temperature and the dew (high relative humidity) that often occurs in these weather conditions.

Application of Plexipave and Plexitrac products in the fall can be risky because the weather patterns are changing.  The major change is a decline in average temperature.  The opportunities for proper curing diminish; soon they do not exist at all as winter weather begins.

No matter how much we may wish to change the weather conditions or the physical properties of water base coatings, the reality is that certain weather and site conditions are needed to make the system dry, cure and develop the physical properties required for long-term performance.

Our technical department can provide additional information upon request.