Coating defect

Runs and sags

Drips, curtains or teardrop shapes on vertical surfaces where the wet paint has flowed downward.

Runs and sags: the surface as you see it, and a schematic cross-section.

Causes

Wet film too thick for the product.
Too much thinner, or paint too warm or too cold for its viscosity.
Gun held too close or moved too slowly.

Prevention

Check wet film thickness as you go and build thick films in passes.
Keep thinner and temperature within the data sheet limits.

How it is assessed

Visual inspection; DFT readings across the sag show the excess thickness.

Telling it apart

Orange peel: Orange peel is paint that did not flow enough. Runs and sags are paint that flowed too much.
Holidays and misses: Above a curtain the film is often thin; check for thin areas and holidays there.

Repair

Brush out while wet. Once cured, sand or abrade the sag level and recoat if the DFT or appearance requires it. The specification and the coating manufacturer have the final word on the repair procedure.

64 practice items in the members area mention runs and sags (CIP 1: 16 · CIP 2: 30 · FROSIO written: 18).

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.