Coating defect

Blushing (solvent blush)

A milky, cloudy haze or pale, low-gloss spots on a drying film.

Blushing (solvent blush): the surface as you see it, and a schematic cross-section.

Causes

Fast solvent evaporation cools the wet film below the dew point, and moisture condenses in it.
Spraying in humid air, or blowing air on the wet film.
Fast-drying lacquers and other evaporative coatings are the most prone.

Prevention

Watch the dew point margin, and use slower thinners in humid conditions.
Do not blow air onto a wet film.

How it is assessed

Visual. It is a physical effect of moisture, unlike amine blush, which is a chemical reaction on epoxies.

Telling it apart

Amine blush: Amine blush is a chemical product on the surface of amine-cured epoxies, greasy and water-soluble. Solvent blush is moisture trapped in the film of a fast-drying coating.
Chalking: Chalk forms over months of weathering and wipes off as powder. Blush forms while the film dries.

Repair

Light blush may clear with a slower thinner. Otherwise abrade and recoat. The specification and the coating manufacturer have the final word on the repair procedure.

16 practice items in the members area mention blushing (CIP 1: 7 · CIP 2: 5 · FROSIO written: 4).

Try it in an exam-style question. The free readiness check shows the question style, explains every answer and gives you a dated study plan.

Take the free readiness check See the tracks

About this page

Written from coating practice and the published rating standards, in our own words; the drawing is schematic. Checked on 2026-10-14; errors go in the corrections log. CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.