Amine blush is a thin, waxy, or greasy residue that sometimes forms on the surface of curing epoxy, caused by the amine hardener reacting with moisture and carbon dioxide in the air instead of only with the resin.
What Causes Amine Blush
Amine blush shows up most often in cold, humid conditions, since low temperatures slow the epoxy’s cure and give the amine more time to react with airborne moisture before the coating fully sets. Poor ventilation and high humidity during the cure window make it worse. Some hardener chemistries are also more prone to blushing than others, which is why product selection matters in humid or seasonal climates.
Why Amine Blush Is a Problem
Left in place, amine blush interferes with adhesion between coats, since a new layer applied over a blushed surface may not bond properly and can peel or delaminate later. It can also affect the appearance and clarity of clear topcoats, leaving a cloudy or greasy-looking finish even after the coating has fully cured.
Removing and Preventing Amine Blush
Amine blush is water soluble, so it can usually be removed by scrubbing the surface with water and a mild detergent, or with a dedicated blush-removing cleaner, followed by a clean water rinse and full drying before recoating. To prevent it in the first place, keep the job site warm and dry during the cure window, use dehumidifiers in humid conditions, and choose a hardener formulated for cold or blush resistant cure when working in less than ideal weather.
