Who Regulates Exterior Paint Durability Testing?

Paint is a popular product for enhancing the appearance of building interiors and exteriors. Paint properties extend beyond visual impact, and paint coverage and durability are significant quality criteria.

Paint durability is the resilience of dried paint film to withstand routine maintenance like wiping, brushing, and cleaning. Paint coverage describes the spreading rate of paints and coatings on a given material or surface.

Several testing procedures have been developed to test paints on how they perform over time when subjected to environmental factors such as UV light, chemical attack, and physical contact. The ASTM standards are instrumental in specifying and evaluating the physical and chemical properties of various paints and coatings.

The exposure of paints and coatings comprises the single largest segment of weather durability testing, both outdoors and in laboratory artificial weathering. Atlas offers the most advanced options for durability testing of paints and coatings.

Paint durability testing methods

• Exposure to the elements: Paint is exposed to sun, moisture, humidity, high temperatures, and temperature fluctuations to determine the impact on its performance. This is the single largest segment of weather durability testing.
• Controlled laboratory tests: Industry-standard tests are conducted in a controlled laboratory setting to evaluate the integrity and performance of the paint formulation on different substrates. These tests are designed to be more rigorous and aggressive than a real-world environment to give a good indication of performance and lifecycle.
• ASTM standards: The ASTM has developed standards and test methods to evaluate the physical and chemical properties of paints and coatings. These include tests for water resistance, corrosion resistance, adhesion, and colour and gloss retention.
• Specialised tests: Depending on the application, specialised tests may be conducted to evaluate coating durability. For example, the automotive industry has developed standard tests for chemical and stain resistance, while the textile industry has tests for hydrostatic resistance, abrasion resistance, and stain resistance.
• Real-world tests: Some companies conduct real-world tests by exposing paint to outdoor conditions over an extended period to build a library of data for comparative purposes.
• Combinatorial testing: This method evaluates multiple parameter values rather than just pairwise testing, allowing for the assessment of the impact of interactions between different conditions on system failures.

Environmental factors affecting paint

The environmental impact of paint varies depending on the type of paint used and the mitigation measures. Traditional painting materials and processes can have harmful effects on the environment, including the use of lead and other additives.

Temperature Fluctuations

Temperature changes throughout the day can cause issues with paint coatings. In hot climates, paint may dry too quickly or blister due to extreme heat, leading to cracking or peeling over time. Conversely, in cold climates, paint may take much longer to dry, resulting in more dirt and dust particles adhering to the surface before it fully cures. Both scenarios can lead to incomplete adherence to the painted surface, compromising its protective qualities.

Humidity Levels

High humidity levels inhibit the drying process of paints, causing them to form bubbles and flake off easily when dry, leading to poor coverage and protection for the underlying materials. On the other hand, low humidity levels can cause paints to become brittle and crack easily when dried due to their inability to retain moisture, making them susceptible to damage.

Ultraviolet (UV) Rays

UV rays from sunlight tend to fade colours over time, necessitating more frequent recoating. While applying a coat of UV-resistant finish, such as epoxy resin or polyurethane, can help minimise this effect, it won't completely eliminate it.

Exposure to Chemical Elements

Exposure to chemical elements like acid rain from air pollution and saltwater spray from oceanic conditions can significantly reduce the lifespan of paint coatings. Certain metals within the paint can corrode or rust if left unprotected by appropriate paints or sealants. Similarly, prolonged exposure to extreme sunlight without any shade or protection can cause certain types of paints, especially those used on exterior applications like house paints or vehicle wraps, to fade quickly, reducing their aesthetic appeal and protective properties.

Volatile Organic Compounds (VOCs)

VOCs are emitted from solids or liquids as vapours or gases and can potentially become hazardous air pollutants. They have adverse short-term and long-term health effects, including eye irritation, breathing difficulties, headaches, nausea, kidney damage, nervous system damage, and even cancer. VOCs can also contaminate groundwater and drinking water supply wells, creating additional risks.

Paint adhesion problems

Causes of Paint Adhesion Problems

• Poor surface preparation: If the surface before painting has dirt, dust, grease, mould stains, or moss, it can lead to poor adhesion of the paint, resulting in the paint film being removed from the surface.
• Weather conditions: Exterior paints exposed to harsh weather conditions such as sunlight, UV rays, heat, wind, rain, and pollution can cause the paint film to deteriorate over time.
• Paint film deterioration: The adhesion of the paint film to the wall may decrease over time, leading to the low paint adhesion problem.
• Inappropriate paint choice: Some paints are not suitable for certain surfaces, so choosing the right paint for the specific surface is essential.

Tips to Improve Paint Adhesion

• Surface preparation: Ensure the surface is clean, free from dust, dirt, grease, and other foreign matter, and completely dry. Repair any cracks before coating.
• Primer application: Apply a suitable primer to the surface to enhance adhesion and protect the surface substrate from moisture and stains.
• Paint selection: Choose a paint that is resistant to weather conditions and suitable for the specific surface.
• Application technique: Use the correct painting equipment and techniques to achieve a smooth and even paint film.

Paint drying and curing

During the paint curing process, the paint hardens and preserves, making it ready for everyday use. Factors such as temperature, humidity, and ventilation can affect the curing time. It is important to allow adequate time for the paint to cure before rearranging furniture or putting the room back together.

To check if the paint has fully cured, you can perform a simple test by gently pressing your fingernail or a knife onto the paint surface. If it leaves an indent, the paint is not fully cured. If the surface remains hard and no indent is visible, the paint has cured.

Paint manufacturers usually provide guidelines on the drying and curing times for their products. However, it is essential to follow the instructions and allow sufficient time for the paint to cure completely. This will ensure a satisfactory paint job and prevent issues such as streaks, peeling paint, or paint flaking.

Paint coverage and its impact on durability

Paint coverage and durability are significant quality criteria that allow for a more precise product choice, reduced wastage, and a longer-lasting paint film. Paint coverage describes the spreading rate of paints and coatings on a given material or surface. It is typically indicated on a product label as square meters per litre of product. Knowing the paint coverage helps in planning a painting project by providing information on the necessary amount of paint for a given surface size. This knowledge allows consumers to save money and reduce waste.

The paint coverage depends not only on the surface but also on its wear and tear conditions. The type of paint also affects coverage. For instance, the EU Ecolabel sets out the minimum surface area that one litre of indoor paint should cover (8 m2/l) and outdoor paint (6 m2/l).

The durability of paint is its resistance to mechanical exposure, measured by its washability, wet abrasion, and scrub resistance. Paint durability is directly linked to the routine maintenance of the surface. The level of washability should ensure that the painted surface can be cleaned easily without damaging its quality.

The EU Ecolabel requires paints to comply with certain efficiency requirements, including the evaluation of paint product coverage and durability. Paint durability can be enhanced by adequate surface preparations and the appropriate choice of paint.

Frequently asked questions