Blistering

Description of problem: 19-blistering.jpg
    Even the best paints will let water vapors through.  When the
   vapors go inside the film, they can lead to the weakening of the
    adhesion between different coats.  Bubbles containing water
   may show through.

 

Causes:         
    – Contamination of the surface before spraying.
    – Insufficient ground coat.
    – Insufficient topcoat.
    – Inappropriate thinner.
    - Final coat was exposed to high humidity before it was completely hard.
    – Continuous exposure to high humidity / contaminated air supply.
    – Residue of sanding water in corners, edges, rebates and below decorative strips.
    – Insufficient isolation of polyester.

 

Remedy:
    Sand carefully until all the bubbles have disappeared: In other words, if the bubbles
    are in the topcoat, it will have to be removed. There is always the possibility that the 
    sanding residues fill the holes of the bubbles.  The humidity that is withheld may
    damage the substrate. The only way to get around this kind of problem is to sand all  
    the way through to the bare metal, clean with Valox, sand and repaint.

 

Note:
    The presence of these types of bubbles around the headlights
    or taillights may be an indication of rust coming form
    underneath.  Some micro holes in the metal might be letting
    the water through.  The bottom of the vehicle should be well
    protected.