You pull the plastic off your project and the cured epoxy feels waxy or greasy, or it has a cloudy film. That’s usually amine blush, and it’s easy to fix once you know what it is.
What causes amine blush
Amine blush is a by-product of the curing reaction in many amine-hardened epoxies. It shows up more in cool, humid conditions and on thicker coats. The WEST SYSTEM surface preparation guide notes that it can clog sandpaper and stop the next coat, paint, or varnish from bonding properly.
How to remove it
- Let the epoxy cure fully.
- Wash with clean water and an abrasive pad such as a Scotch-Brite general-purpose pad. Blush dissolves in water, while many solvents don’t remove it well.
- Dry right away with plain white paper towels, so the dissolved blush doesn’t dry back onto the surface.
- Sand any glossy spots that remain (WEST SYSTEM suggests 80 grit), or wet-sand, which removes blush as you go.
Soap, ammonia, or bleach aren’t needed and can leave their own residue (Epoxyworks: Let’s Talk About Amine Blush).
How to prevent it
- Work warm and dry. Keep the room and the surface inside the temperature range on your product’s data sheet, and avoid humid days or running propane heaters, which add moisture and CO2.
- Recoat while the previous coat is still tacky. The layers bond chemically and blush isn’t a problem.
- Choose a low-blush or “non-blushing” hardener when clarity matters.
Planning a pour? Read curing epoxy in cold weather.