Alligatoring

Patterned cracking in the surface of the paint film resembling the regular scales of an alligator.

Possible Cause

• Application of an extremely hard, rigid coating, like solvent-based enamel, over a more flexible coating, like a water-based primer.
• Application of a topcoat before the undercoat is dry.
• Natural ageing of oil-based paints as temperatures fluctuate. The constant expansion and contraction results in a loss of paint film elasticity.

Solution

Old paint should be completely removed by scraping and sanding the surface; a heat gun can be used to speed work on large surfaces, but take care to avoid igniting paint or substrate. The surface should be primed with high quality water-based primer, then painted with top quality exterior water-based paint.

Images courtesy of the Paint Quality Institute from Dow Coating Materials