With resinous softwoods, the escaping resin can cause discolouration at knots. The pigments in the resin can cause yellowing on the paint surface, especially with white opaque coatings. Preventing these discolourations requires a special primer.

Teknos developed the latest knot sealer TEKNOCOAT AQUA PRIMER 1867-50 for this very purpose. The acidic white primer is specially designed for knotty pine wood on interiors. TEKNOCOAT AQUA PRIMER 1867-50 binds the colour substances in the resin and ensures that they remain inside the wood. This prevents knots in pine from causing discolourations in the topcoat treatment with white or light opaque paint.