Blocking 4 Patchiness

PATCHINESS

PATCHINESS

Poor sheen or colour uniformity, especially recognisable when looking at the surface at an angle.

POSSIBLE CAUSES

• Painting over surfaces with variable texture and porosity (eg. joins between plasterboard). • Failure to properly prime or undercoat a substrate. • Inconsistent application technique. • Poor conditions during the application or drying period (eg. high temperatures and/or high humidity).

SOLUTIONS

• New substrates should be primed/sealed before applying the top coat to ensure a substrate that is uniform in porosity. • Ensure paint is applied using a consistent application technique (eg.applying even roller pressure from top to bottom) whilst maintaining a wet edge. • Ensure application and drying conditions conform to manufacturer’s recommendations.

PEELING, FLAKING AND CRACKING

PEELING, FLAKING AND CRACKING

The formation of defined breaks in the paint film, localised loss of adhesion between the paint film and the substrate or the complete detachment of the paint film from the underlying surface or substrate.

POSSIBLE CAUSES

• Painting over an unsound substrate (e.g. weathered timber, weak or underbound concrete or plaster). • Painting over contaminants or loose materials. • Painting over an excessively smooth surface which is difficult to bond to. • Prepcoat (primer, sealer or undercoat) not applied, of poor quality or incorrect type used for the substrate. • Lack of maintenance of existing coatings.

SOLUTIONS

• The extent and causes of the problem need to be clearly identified, the causes removed and the old paint stripped back to a sound substrate (some substrates may be beyond repair and will need to be replaced) before any new painting commences.