What is ‘Dew Point’?

We have all experienced ‘Dew Point’ at some stage. Condensation on windows is an obvious example. Dew Point is the temperature at which the air can no longer hold its water vapor and starts to form water droplets i.e. condensation. Condensation forms when air temperature lowers, reducing the amount of energy available to keep the water in vapor format. For example, a window forms condensation when the cool night air hits the outside surface of the glass, lowering the surface temperature and the humidity in the house is high enough to cause condensation on the inside of the glass surface. When painting, it is essential that you are able to paint a surface and avoid condensation forming during the application and drying stages. The optimum surface temperature for paint application is normally around 6°F above the Dew Point; however some products may be more or less tolerant. When working with Interlux products, if in doubt, it’s always worth checking the relevant technical data sheet – available on our website – for further advice. Dew Point can be calculated using the relative humidity and the air temperature; however, Dew Point ‘look-up’ tables are widely available via the internet.