Moisture blistering

Cause

• Moisture absorbed by the substrate.
• Insufficient substrate drying after wet sanding (particularly a problem with polyester products).
• Condensation due to temperature fluctuations. 
• Polyester products not isolated.
• Damp compressed air.

Prevention

• Dry-sand and isolate polyester products.
• Ensure that the supplied compressed air is clean.

Remedy

• Sand down the affected area completely, matt-sand the unaffected remaining surface, clean with silicone remover, apply surfacer and then respray.