There are two main types:

1. Large blisters at random places on a vehicle body. Size from 1/4" up to perhaps 1/2" when they become scabs. Usually due to the formation of rust on the steel.

This is fairly self evident, is regarded as a corrosion problem and is easily dealt with by the refinisher with the following recommendations:

Abrade back to metal

Remove ingrained rust with Deoxidine 125.

Spot prime with Long Life Etch Primer.

Apply undercoat and colour coat as a local repair, or over complete panel if several blisters or scabs exist.

2. Micro blistering, which if not attended to in its early stages will eventually lead to complete failure of the paint film with consequent rust formation.

Causes and rectification are various and a brief guide to these is given below.