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.
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.