Formation of patches
Description of the defect
Blotches or dot-shaped discolourations of the surface finish, evenly or unevenly limited, with uniform or non-uniform distribution on the surface finish.
Cause of the defect
There are various possible causes, here are some examples:
• Brownish blotches can be caused by the reaction of a CN lacquer with certain substances (amino-compounds) in specific UV coatings
• By release from rubber compounds (for instance rubber feet/protectors on telephones, Hi-Fi equipment, vases, ashtrays, etc.)
• Contamination by assembly foam residues (these are colourless at first and only turn yellowish-brown over the course of time)
• Remains of iron or other rusting metals in the wood (such as metallic sandpaper residue) can cause black spots when combined with water (such as when using Hydro stains or lacquers)
A discoloured surface can only be recovered by completely sanding off the layer of lacquer and then re-coating with a PUR-System polyurethane. If the blotches/discolourations are directly on or in the wood, these must first be removed by suitable means (sanding, washing, etc.) before a renewed attempt at applying a finishing coat.