How to Achieve an Incredible Looking Finish When Applying a Moisture Cured Paint
You just applied the final coat of a moisture cured paint or coating. It's still wet and so far, everything looks great. You call it a job well done and leave the piece to dry thoroughly. Later you come back to inspect your work and see micro bubbles have formed in the coating. Now you must either deal with it the way it is, or sand down the bubbles and apply another coat. User error is the main reason moisture cured paints and coatings form bubbles, and it's easily avoided.
What Is a Moisture Cured Paint or Coating?
A moisture cured paint or coating cures in the presence of atmospheric moisture, forming a protective film by reacting chemically with the moisture in the air. These are one-part (1K) formulations and include clear coats like DiamondFinish Clear, rust preventative coatings like RustSeal and BlackTop, as well as KBS MAXX and other paints, coatings, and sealants.
Why Moisture Cured Coatings Perform So Well • Withstand pooling water. • Produce a hard, durable, highly reflective surface. • Offer good adhesion characteristics, and cure well in humid environments where other coatings struggle. |
Moisture cured paints and coatings are made up of pigments, additives, resins, and solvents. Because they cure in the presence of water vapor, the formulation is solvent based rather than water based. As the paint or coating begins to dry, the solvent evaporates and the resin component remains, creating a hard, non-breathable coating that resists stains, contaminants, and rust.
Why Moisture Cured Paints and Coatings Can Form Bubbles
Those nasty little bubbles you may find in a dried coating are typically formed by gas and vapor pressure within the paint. This usually happens when a coat is applied too thick and a film, or skin, forms over the top of the still-wet, solvent-rich coating — much like pudding that has skinned over. The solvent gas underneath has difficulty evaporating through that film and becomes trapped, a condition known as solvent entrapment, which forms bubbles under the skin.
⚠ Bubbling vs. Blistering Blistering is a different problem than bubbling. It happens when a moisture cured coating is applied during high humidity, or onto a wet surface, essentially a wet-on-wet application. |
The resulting bubbles dry in place as the coating cures. Beyond looking bad, this can compromise the protection the coating is meant to provide, since bubbles can turn a hard, non-breathable film into a permeable, Swiss-cheese-like structure that lets moisture, oxygen, and contaminants pass through.
Tips for Applying Moisture Cured Coatings
Avoid Bubbles With Patience and Prep Apply thin coats. Instead of a couple of thick coats to finish the job quickly, apply multiple thin coats, giving each one sufficient time to dry and off-gas solvent. With RustSeal, that means waiting until a coat is dry-to-the-touch and leaves no fingerprint, typically 2-6 hours depending on temperature and humidity, before recoating. Watch the conditions. Don't apply moisture cured products in rainy or excessively humid conditions, or onto wet surfaces. Don't overwork the brush or roller. Going back and forth repeatedly forces solvent gases out faster than the coating is designed to release them, interfering with proper self-leveling and curing. |
Ready for a Flawless Finish? Whichever moisture cured coating you're using, thin coats and patience are the key to a bubble-free result. |
Frequently Asked Questions
Why did my moisture cured paint form bubbles? Bubbles usually form when a coat is applied too thick and a skin forms over the still-wet, solvent-rich paint underneath. The trapped solvent gas can't escape through that skin, a condition called solvent entrapment, and it shows up as bubbles once the coating cures. |
What's the difference between bubbling and blistering? Bubbling is caused by trapped solvent gas from a coat applied too thick. Blistering is a different problem, caused by applying a moisture cured coating during high humidity or onto a wet surface, essentially a wet-on-wet application. |
How do I avoid bubbles when applying RustSeal, BlackTop, or KBS MAXX? Apply multiple thin coats instead of a couple of thick ones, and give each coat enough time to dry and off-gas solvent before recoating. For RustSeal, that typically means waiting until the coat is dry-to-the-touch and leaves no fingerprint, usually 2-6 hours depending on temperature and humidity. |
Can overworking the brush or roller cause bubbles? Yes. Going back and forth repeatedly with a brush or roller forces solvent gas out faster than the coating is designed to release it, which interferes with proper self-leveling and curing and can contribute to bubbling. |
Ready to get a flawless finish? We can help you pick the right moisture cured coating for your project. Ships fast from Valparaiso, IN. Shop RustSeal Shop BlackTop Shop KBS MAXX Contact KBS Coatings |