Timber staining
Staining from timber is a brownish or tan discolouration of acrylic house paint that can occur when the paint is applied over certain types of bare wood. Naturally it can be quite unsightly on white or light-coloured paints. Although the discolouration will often bleach out in open, exposed areas, it can be very persistent in damp areas that receive little sunlight. Staining commonly occurs when water soluble tannins found in some kinds of wood, particularly cedar, redwood and beech, seep through waterborne paint and discolour it.

The condition can also occur over painted knots of other wood species especially some types of pine, and it can be sometimes observed where previously painted pine has peeled down to the bare wood, permitting the staining material to rise to the surface.

To avoid staining, bare wood should be primed with Resene Wood Primer. This primer will keep the wood tannins from bleeding into the topcoat, except in the most severe cases.

Note that for cedar, a pre-treatment with Resene TimberLock is strongly recommended. This is to help bind up and strengthen the timber surface of the very soft cedar. This will not seal in stains and is not needed prior to Resene WB Woodsman.

Most often associated with Cedar and Redwood timber, some native Beech will also stain. Stains usually appear immediately but may appear after rain. A barrier coat of enamel paint is the only way to fix these problems. Staining will only occur if waterborne paints are used. A primer coat of Resene Wood Primer should seal off stains that do appear.

Some imported hardwoods may also stain and decking timber left unpainted can cause stain splashes onto surrounding painted weatherboards.