When a home is being constructed, paints are subjected to a wide variety of drying conditions, which can lead to differences in appearance between the original coat and subsequent touch-up areas after the paint has fully cured. A new standard, ASTM D7489, Practice for Evaluating Touch-Up Properties of Architectural Coatings Under Various Environmental Conditions, covers variations in color, gloss and sheen that impact the touch-up capacity of a paint.
According to Douglas Mall, D01.42 member and architectural coatings applications and formulation development specialist, UCAR Emulsion Systems and Monomers, ASTM D7489 brings together a variety of different testing protocols that have been used for touch-up evaluation. "By using ASTM D7489, it will be easier for contractors to communicate with laboratories what conditions generated product failure, with a much better chance of the laboratory being able to replicate the failure and make changes that would correct the product deficiency," said Mall.
The standard will be used by chemists in paint laboratories as well as technical service personnel in the field. Future work on ASTM D7489 will include reproducibility and repeatability studies, especially in the area of spray application. "The next step for this standard is to develop it further as a test method, selecting more common application methods and conditions," said Mall. "We would like to get feedback on the current practice and its usefulness."
For the second new standard, paint companies and raw material suppliers will be able to use a new ASTM standard to assess the capability of architectural coatings for blocking ink stains from bleeding through to a topcoat. The standard, ASTM D7514, Test Method for Evaluating Ink Stainblocking of Architectural Paint Systems by Visual Assessment, represents a compilation and synthesis of methods that are currently being used to evaluate stainblocking.
According to Neal Rogers, group leader, research and development, Cook Composites and Polymers Co., ASTM D7514 is the result of a survey taken by Subcommittee D01.42 of various methods for measuring the stainblocking capabilities of coatings.
"The development of ASTM D7514 provides a means to critically evaluate and differentiate between different resin technologies used in the manufacture of stainblocking primers," said Rogers.
While ASTM has a test method for the assessment of stainblocking tannins in wood (ASTM D6686, Test Method for Evaluation of Tannin Stain Resistance of Coatings), many coatings, particularly interior paints, are applied to previously painted surfaces rather than the bare wood that is covered by ASTM D6686, according to Rogers.