What is Amine Blush?
March 07,
2025
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By David Johnson, WRA Technical Applications Director. In this article, we answer all your questions about amine blush.
What Is Amine Blush?
Amine blush is a waxy byproduct that appears as epoxy cures. It can prevent varnishes and other coatings from bonding. However, there are simple steps you can take to avoid it becoming a problem. As epoxy cures in contact with moisture, a greasy or waxy film known as amine blush is produced on the surface of the cured epoxy. Its appearance varies depending on the moisture level in the air, but it is typically more noticeable in cool, humid conditions. You may not always see it, or it may present as a thin, greasy, or dull layer.
Why Is Amine Blush a Problem?
Amine blush itself isn’t a problem; rather, the issues arise when it interferes with adhesion. If you continue working without removing the blush, it will prevent varnishes, additional epoxy layers, and other coatings from bonding properly.
Can You Prevent Amine Blush From Forming?
You cannot completely prevent it from forming, but you can manage it effectively by using WEST SYSTEM® 879 Release Fabric (Peel Ply). Since the blush will form on the peel ply rather than the cured epoxy, it provides a convenient way to eliminate the issue. Peel ply is a finely woven nylon fabric that does not bond to epoxy.
To use peel ply, follow the application instructions: ensure it is thoroughly wetted out, allow the epoxy to cure, and remove the peel ply before applying the next coating. The blush will have formed on the peel ply rather than on the epoxy itself. Once removed, the fine woven pattern left behind creates a textured surface that is ready for bonding.
For more on on prevention, read the article “Minimizing Amine Blush” by former GBI Technical Advisor Tom Pawlak, and GBI Senior Chemist Tim Atkinson.
How Can You Remove Amine Blush?
Attempting to sand a surface with blush on it will clog your sandpaper and cause the blush to penetrate deeper into the workpiece. Since amine blush is water-soluble, removing it is quite simple! All you need is a bucket (or spray bottle), warm soapy water, and a Scotch Brite pad. Dampen the affected surface with water, scrub thoroughly using the pad, and then wipe dry with paper towels. That’s it—your surface is now ready for the next step.
Do All Epoxies Create Amine Blush?
While slower hardeners, such as WEST SYSTEM® 209 Extra Slow Hardener® and 207 Special Coating Hardener®, produce less blush than faster-curing epoxies, it is best to assume that some amine blush will always form when using an amine-based epoxy system. Removing it is quick and easy, whereas ignoring it can lead to adhesion issues that are far more time-consuming to fix.
For a more in-depth or ‘technical’ read, check out “Let’s Talk About Amine Blush” by GBI Vice President of Technical Services, Jeff Wright.
