ASTM D7539 Standard Practice for Humidity Regulation of Pavement Marking Coatings test Boards using a laboratory defines a standard environment with a temperature of 23±2°C, a relative humidity of 50± 5%, and no airflow for the normal regulation and testing of paints, varnishes, lacquers, and related materials.
Meaning and use

5.1 The drying rate of organic coatings varies with temperature, air flow and relative humidity. In particular, the drying rate of water-based coatings depends on the evaporation of water and is therefore more dependent on relative humidity than solvent-based coatings or 100% solid coatings. Without some control over drying conditions, the drying rate of water-based coatings measured in the laboratory under ambient conditions cannot be adequately replicated. A test chamber providing a device for controlling relative humidity above ambient humidity and minimizing the effect of changes in airflow at ambient room temperature is described. If needed,

5.2 This practice is particularly useful for testing the drying rate of waterborne pavement marking (traffic) coatings, where rapid drying at high ambient humidity is an important feature. For waterborne traffic coatings, test chambers can be used to assess dryness to non-absorption at high ambient humidity (test method D711) and washable resistance (practice D7377 and D7538).

ASTM D7539-2015 Standard Practice for Humidity Regulation of Pavement Marking Coatings Test Boards Using Laboratories

Step 1: Scope

1.1 Specification D3924 defines a standard environment with a temperature of 23±2°C, a relative humidity of 50± 5% and no airflow for the normal conditioning and testing of paints, varnishes, lacquers and related materials. The practice describes a test chamber that allows the control of relative humidity above the ambient relative humidity and minimizes air flow to regulate the test board at elevated relative humidity and room temperature.

1.2 Values in inches to pounds shall be considered as standard values. The values given in parentheses are mathematical transformations of SI units and are for reference only and are not considered standard.

1.3 This standard is not intended to address all safety concerns, if any, associated with its use. It is the responsibility of users of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory restrictions prior to use.