Formation of patches

Formation of patches

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)

• Wood that is rich in tannin (e.g. oak) or wood that has water-soluble wood contents (such as ash) can suffer from colour change when coated with Hydro lacquers

• 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)

Defect solution

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.