Description of the defect

Brown discolouration of a stained wood surface when using an unsuitable polyurethane system. Reaction between peroxide (bleaching agent) and isocyanate (polyurethane hardener).

Cause of the defect

Using a polyurethane lacquer with a non-peroxide-resistant hardener on a stained wood surface.

Defect solution

The discoloured surface can only be recovered by sanding off the layer of lacquer and then recoating with a polyurethane system with a peroxide-resistant hardener.