# Solvent entrapment and popping

Source: https://coatmentor.com/defects/solvent-entrapment/ · Updated 2026-10-04

Bubbles, blisters or small craters in the film, and a film that stays soft. Popping is air or solvent bursting through the surface.

*Figure: Solvent entrapment and popping: the surface as you see it, and a schematic cross-section.*

## Causes

- Film far above the maximum DFT: the surface skins over and traps solvent below.
- A full wet coat over a porous primer such as inorganic zinc without a mist coat.
- Overcoating before the minimum recoat time.

## Prevention

- Keep DFT within the specified range.
- Use a mist coat over porous primers; respect recoat times.

## How it is assessed

Visual inspection. Check hardness and DFT. Trapped solvent can later cause blistering in service. Note: ISO 19840 is for CIP 2 and FROSIO only.

## Repair

Remove soft or bubbled coating and reapply correctly; minor surface popping may be abraded and overcoated if the spec allows. The specification and the coating manufacturer have the final word on the repair procedure.

**6** practice items in the members area mention solvent entrapment and popping (CIP 1: 1 · FROSIO written: 5).

## Related

- **Concepts:** [Drying, curing and recoat windows](https://coatmentor.com/learn/cure-and-recoat/) · [Zinc-rich primers](https://coatmentor.com/learn/zinc-rich-primers/) · [Dry film thickness measurement](https://coatmentor.com/learn/dft-measurement/)
- **Standards:** [ISO 19840](https://coatmentor.com/standards/iso-19840/) · [SSPC-PA 2](https://coatmentor.com/standards/sspc-pa-2/)

## About this page

Written from coating practice and the published rating standards, in our own words; the drawing is schematic. Checked on 2026-10-04; 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.