Blistering

Symptoms

Large or small blisters, possibly only in topcoats of the system.

Generally only local loss of adhesion of paint system.

Cause

Application over localised contamination (e.g. grease, oil, resin) Humidity or gas vapour formation from the substrate Solvent could be trapped between coats of the paint system if the primer or mid coat has not been allowed to dry fully. Incorrect coating system, e.g. quick drying top coat, at which the contained organic solvent causes blisters. Solution

Coating layers that are not sound should be removed. After the right pre-treatment against moisture penetration, a new system should be applied. Touch up bare spots with primer and finish with finish topcoat.