Timber Staining/Dyeing & Cleaning

The tradesperson starts by checking the timber. Is it dry, sound and free of mould? Are there old layers of varnish, oil or finish still on it? The answers decide the rest of the process.

Next comes cleaning. New sawn timber is usually dusty from cutting, and pine or spruce often has sticky resin around the knots. Older outdoor timber tends to be grey, mossy or marked with dark patches from damp. Light dirt comes off with a brush and a suitable wood cleaner. Resin is best removed with the solvent the stain manufacturer recommends. If water is used for cleaning, the wood must dry out completely afterwards. Feeling dry to the touch is not enough.

Once dry, the surface is sanded along the grain and all sanding dust is removed. Only then is the stain applied, evenly and without stopping halfway across a surface, so that no lap marks appear. After the stain has dried, the protective coat goes on, chosen according to whether the timber will stay indoors or outdoors.

A stain mainly changes the colour. It soaks into the surface and brings out the growth rings, but it does not form a layer that resists water, sunlight or wear. A coloured protective finish, often sold as a translucent wood finish or exterior wood stain with protection, combines colour and protection and is the usual choice outdoors, for fences, pergolas, soffits and cladding. Varnish forms a hard film and suits indoor work such as stairs, handrails and furniture. Outdoors it can crack and peel as the timber moves.

Stains are either water-based or solvent-based. Water-based stains smell less, but they raise the grain, so the surface feels rough afterwards. That is why the wood is often dampened lightly first, left to dry and sanded. Solvent-based stains usually penetrate deeper but need good ventilation. In both cases it pays to stick to one system from one manufacturer. When brands are mixed, layers sometimes dry poorly or fail to bond.

An important point for structural timber: stain does not replace preservative treatment against wood-boring insects and fungal decay, which is recommended for load-bearing roof timbers. If a beam needs both protection and colour, check the order of the coats and whether the products are compatible in their technical data sheets.

The simplest case is new, dry, smooth timber lying on trestles before fitting. It can be treated on every side, including the cut ends, and the work goes quickly. These situations make the job slower and therefore more expensive:

• The timber is already fitted and hard to reach, such as ceiling beams or roof soffits
• Old varnish, oil or finish is still on the surface and has to be sanded off
• The wood is grey, covered in moss or has mould
• The pieces are intricate, with many joints, edges and corners that have to be done by hand
• The surroundings need covering, for example the facade, windows or floor
• You want the new colour matched exactly to older timber

Work at height, such as on soffits or gables, belongs with a firm that has scaffolding or an access platform and experience of working safely at height.

Timber shows every flaw in the preparation. In practice it often happens that stain goes straight onto dusty or greasy wood. The greasy spots stay pale while the open grain turns dark. Leftover patches of old coating behave the same way and leave blotches.

Other typical mistakes:

• Sanding across the grain, so the stain highlights every scratch
• Staining damp timber, which leads to bubbles and a peeling top coat
• Skipping a colour test, even though spruce, pine and oak take the same stain very differently
• Leaving cut ends untreated, although they soak up the most water
• No protective coat after staining, so the colour fades quickly outdoors
• Too much water pressure during cleaning, which tears up the soft fibres

Why does softwood so often look blotchy? Spruce and pine have harder latewood and softer earlywood rings, and they absorb stain unevenly. Some manufacturers offer a pre-stain conditioner that evens out the absorbency.

A small amount of timber that has not yet been fitted is something you can handle yourself. Work outside in the shade or in a well-ventilated room, and with solvent-based products wear gloves and a respirator as the label instructs.

1. Lay the timber on trestles so that every side can be reached.
2. Check that the wood is dry and free of mould and cracks.
3. Brush off the dust and remove resin from the knots with a suitable solvent.
4. Sand along the grain. For a water-based stain, dampen the wood lightly first and let it dry.
5. Vacuum the dust and wipe the surface with a dry cloth.
6. Test the colour on an offcut of the same timber and let it dry.
7. Apply the stain with a brush or cloth along the grain, covering the full length of each board in one go.
8. Treat the cut ends and edges as well.
9. Let the stain dry for the time the manufacturer states.
10. Apply the protective coat, whether varnish, oil or wood finish, in as many coats as the manufacturer recommends.

Look at the finished surface in daylight and from the side, as this shows the most. When you accept the work, go through these points:

• The colour is even and matches the agreed sample
• There are no blotches, stripes or lap marks between strokes
• No scratches from cross-grain sanding are visible
• The surface is smooth, without raised grain or dust in the coating
• Cut ends, edges and joints are treated the same as the faces
• The protective coat has been applied and is not tacky
• The surroundings are clean, with no drips on the facade, windows or floor
• You know which products were used and how to look after the timber