Before painting, the coater must meet the coatings’ parameters. These are clearly specified on the paint manufacturer’s product data sheet.

Relative Humidity (RH) and Delta T (TΔ) are the two climatic values which are specified on data sheets.

The Elcometer 309 Delta T Hygrometer provides a simple and fast measurement of these two critical characteristics.

• Delta T (TΔ): The difference between the surface temperature (Ts) and the dewpoint temperature (Td). When TΔ is less than 3ºC (5ºF) painting should not occur.
• Relative Humidity (RH): This is the amount of water vapour taken up by air. Expressed as a percentage, RH is dependent on the air temperature. Typical maximum RH values specified by paint manufacturers are between 75% and 85%.