What is amine blush?
Amine blush is a waxy, often oily film that appears on epoxy coatings during curing in cool or moist conditions, formed when amine compounds rise to the surface and react with atmospheric CO2.
When epoxy cures in Ontario's humid climate or during cooler months, chemical compounds called amines can migrate to the surface and form a thin, waxy layer known as amine blush. This residue typically appears as a cloudy or oily film on the cured epoxy and is a byproduct of the resin hardener reacting with carbon dioxide in the air.
Amine blush becomes a problem because it sits between the first epoxy coat and any topcoat, creating a weak bond. If the blush is not removed before recoating, the second layer will not adhere properly, leading to peeling, blistering, or delamination months after application. This is especially common in garages, warehouses, and retail spaces where temperature and humidity fluctuate during the cure window.
Whether amine blush appears depends on several factors: the specific epoxy system used, ambient temperature during cure, relative humidity levels, and air circulation in the space. Cold, damp conditions during early cure stages increase the risk significantly. Removing amine blush requires wiping or light sanding the surface before recoating, adding time and labor to the job. Choosing the right epoxy formulation, controlling the cure environment, and allowing proper cure time before topcoating helps prevent blush from forming in the first place.