# Brush marks

Source: https://coatmentor.com/defects/brush-marks/ · Updated 2026-10-14

Lines of ridges and furrows that follow the brush; very coarse ones are called ropiness.

*Figure: Brush marks: the surface as you see it, and a schematic cross-section.*

## Causes

- Paint too thick for brushing, or the wrong thinner.
- Brushing back into paint that has started to set.
- A hot surface or the wrong brush.
- A coating that levels poorly, applied by brush where the data sheet expects spray.

## Prevention

- Bring the paint to brushing viscosity with the recommended thinner.
- Finish with light strokes in one direction and do not rework setting paint.

## How it is assessed

Visual, most visible on gloss finishes; check the film thickness in the furrows.

## Telling it apart

- **[Orange peel](https://coatmentor.com/defects/orange-peel/):** Orange peel is an even, random dimpling from spraying. Brush marks run in lines that follow the strokes.
- **[Runs and sags](https://coatmentor.com/defects/runs-and-sags/):** Runs and sags hang downwards where too much paint flowed. Brush marks are ridges where the paint did not flow out enough.

## Repair

Sand smooth and apply another coat. The specification and the coating manufacturer have the final word on the repair procedure.

## Related

- **Concepts:** [Volume solids, wet film and dry film](https://coatmentor.com/learn/volume-solids/)
- **Standards:** [SSPC-PA 1](https://coatmentor.com/standards/sspc-pa-1/)

## 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](https://coatmentor.com/method/). CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.