Paint Problems and How to Prevent Them
Knowing why paint fails is the best way to get a long-lasting, problem-free paint job.
Although you’ve probably never thought about it, paint manufacturers don’t actually make the ingredients that they use in their paints. Instead, they buy the components from chemical companies and combine them to their own specifications. To ensure that the paint companies are getting the best-performing ingredients, the chemical companies employ paint chemists to formulate and test paint in many ways, including real-world scenarios.
I recently had the chance to meet with employees from the Dow Chemical Company and a team of technical experts who test paint for the Paint Quality Institute (PQI) in a complex near Philadelphia. This “paint farm” has more than 40,000 samples and includes painted building materials ranging from vinyl and fiber-cement siding to steel bridge parts and weathered decking. The complex even includes special racking to hold some of the samples upside down to simulate how paints perform under porch ceilings and soffits, where they won’t be washed by rain.
Because substrates and field conditions can be all over the map, the testers even apply paint samples to weathered primers and sunburned wood to simulate houses that have taken too long to get primed and top coated.
Every few months, the samples are photographed with automated equipment and the photos are checked for changes in appearance. The samples themselves also receive regular visual checks for adhesion, fading, cracks, chalkiness, mildew, and dirt.
The insights gained from decades of testing (the oldest samples date to the early 1960s) have improved both performance and workability. The company’s research also provides excellent guidance on how to solve most common paint problems, which are outlined.
What matters most?
Inorganic trumps organic- Pigments can be broken down into two basic types: organic and inorganic. Organic pigments—which include bright blues, yellows, and reds—fade faster and don’t cover as well as paints made with inorganic pigments. Inorganic pigments—which are usually mined minerals—make blacks, whites, barn reds, yellow ochers, and dark greens.
You get what you pay for- Additives are the most expensive components in a can of paint and have the biggest effect on its workability. Rheology modifiers help paint to go on properly and to resist spattering. Dispersants keep the pigments spread out so that they hide well. Biocides keep bacteria from forming in the can, and mildewcides prevent mold from growing on the paint film. Defoamers break down bubbles caused by shaking, stirring, and rolling. Cosolvents improve workability and allow painting at lower temperatures.
The more solids, the better- Solids are what’s left behind when the liquid carrier evaporates. They give a paint its hiding ability and contribute to its overall durability. Quality exterior house paint has a solids content from 35% to about 45% by volume. Paints on the higher end of the scale cover better and last longer. You can find the exact percentage by checking the product data sheet on the manufacturer’s website.
For more photos and information on the most common paint failures and their solutions, click the View PDF button below.