Preparation

Cleaning

1. In new or maintenance work, surfaces should be free from dirt, oil, grease, wax or other contaminants. Loose deposits including salts arising from preservative or flame-retardant treatment can usually be removed by vigorous brushing and scraping.
2. Primed or previously painted woodstained or varnished surfaces on which the coating is generally in good condition - but soiled and grimy - should be washed with a detergent solution rinsed with clean water and allowed to dry. Washing may be combined with wet abrasion. Solvent cleaning for example with white spirit will be necessary if surfaces are contaminated with oil grease or wax polish.
3. Vegetable growth such as mould algae lichen or moss should be scraped off before applying a sterilising wash to kill residual growths. Dulux Trade Weathershield Multi-Surface Fungicidal Wash* may be used for this purpose. The solution should be applied by brush and left for 24 hours before scraping off dead growth and rinsing with clean water. After treatment time should be allowed for the wood to dry before applying surface coatings.

Sanding and rubbing down

1. Sanding of new or bare wood is necessary only when a very smooth appearance is required. Generally the durability of exterior woodstains is improved if they are applied over a rougher surface.
2. Sharp edges should have been eliminated at the design stage but if there are still any left they should be rounded off with medium grade abrasive paper.
3. Rubbing down between paint coats is necessary to improve adhesion and give a smooth bit-free finish
4. Painted or varnished surfaces in generally sound condition should be rubbed down before recoating. Junctions between coated and bare wood must be feather-edged by carefully rubbing down with abrasive paper.
5. Provided the coating is in good condition surfaces previously treated with woodstain do not usually require sanding. But it is recommended that such surfaces are lightly rubbed down with a fine abrasive plastic pad in the direction of the grain.
6. When rubbing down dry and/or dusting off, wear a suitable face mask to avoid the inhalation of dust.

Treating knots

1. When specifying a paint system one or two thin coats of shellac knotting usually prevents discolouration from knots. Aluminium pigmented wood primers are also effective in preventing resin-staining and their use makes it unnecessary to apply knotting. General knotting solution should not be used with woodstain systems with the exception of white and opaque woodstains when bleached shellac knotting should be used. Bleached shellac knotting should also be used with water-based eggshell satin and gloss paints.
2. Emulsion-based wood primers may be self-knotting but their effectiveness is variable and makers recommendations should be sought.
3. Troublesome isolated knots should be cut out if possible and replaced with clean timber.

Preparation and fillers for Natural Wood Finishes

1. Do not face-fill
   Or rather timber that requires face filling or substantial filling, is probably not suitable for finishing with Natural Wood Finishes. Either replace the wood, switch to a suitable paint, or consider a low build stain such as Dulux Trade Classic Low Build Woodstain.
2. Rake out all areas to be filled and pre-treat with preservative basecoat before filling
   Splits/cracks and areas where defective timber has been removed are where spores may become established. Dulux Trade Preservative Basecoat + will help prevent this as well as improving adhesion and helping to control the moisture content of the timber
3. Use a flexible filler to fill deeper splits/cracks, such as Weathershield Exterior Flexible Filler but finish with a stained filler for an even finish
   Flexible fillers have limited colour choice. Weathershield Exterior Flexible Filler is grey, and the finish colour will be affected if the flexible filler is not covered over with a stained filler which matches the surrounding wood.
4. Powder type fillers should be avoided
   Powder fillers are rarely flexible enough, and may absorb moisture in exterior environments. Exterior or all purpose powder filler must not be used as it will prove too rigid and may also give problems associated to the alkalinity of the white cement ingredients of these fillers.
5. Never use oil based putty for glazing or filling with woodstains.
   Oil based putty will crack on exposure under the low build film, letting in water or fall out causing greater problems.
6. Avoid silicone mastics and fillers.
   These are VERY durable but frequently cause problems with redecoration. They should not be overcoated and the silicone may contaminate surrounding areas of joinery during painting.
7. Use non-ferrous fixings and sink below the surface. Use a suitable coloured stopper; or for interiors, rub in a coloured wax AFTER coating with a Natural Wood Finish.
   Woodstain will not adhere to the wax correctly, and wax may be spread across the surface causing contamination, so it is important not to wax over the finish until you have applied the wood finish.

Stopping and filling

1. Generally woodwork which is to be painted should be primed before it is stopped or filled. This is usually essential when an oil-based stopper or filler is to be used to prevent absorption of the binder - it is less critical for water-based or emulsion-based materials but will help to prevent raising of grain or rust-staining from contact with nails or screws.
2. Nail and screw holes, open joints, deep cracks and similar imperfections should be stopped using a fairly stiff material. Shallow depressions rough or open grain fine cracks and the like should be filled using a more fluid material. Deep holes may need several layers of stopping if excess shrinkage is to be avoided.
3. On woodwork which is to be woodstained or varnished stopping or filling with oil-based materials is usually done after the first coat of stain or varnish has been applied.
4. Water-thinned or emulsion-based stoppers may usually be applied before or after the first coat. Some oil-based fillers can be mixed with stain or colouring to enhance the final appearance of the coated wood and to help disguise areas of filler.

Bringing forward

In maintenance work preparation may involve the removal of defective material from localised areas. Wood exposed in this way should be brought forward or treated as bare wood and given further coats to build up the film thickness to that of the original coatings.

System choice for interior and exterior wood - general

Coatings for wood can be placed in three major categories-paint varnish and stain. Choice of coating for a particular application is based upon appearance maintenance considerations and durability.

Substrate usage - exterior wood

Exterior wood can be divided into two major categories:
Joinery and Sawn wood (often referred to as Rough-Sawn).

1. Joinery where the movement of wood has to be controlled and where a coating which has a high level of permeability would not be suitable. Excessive moisture movement in joinery leads to ssplitting cracking and warping.
2. Sawn wood (often referred to as Rough-Sawn)- such as sawn cladding fencing sheds etc. Here preservation and penetration are the most important coating properties.

Joinery/planed wood

Highly permeable surface-coatings such as low-solids woodstains should not be used on joinery except as a basecoat as they do not provide the right degree of moisture control. Instead a medium build woodstain or high solids or medium permeability alkyd gloss paint system is more suitable.

Sawn wood

With this category one is concerned with wood which is more absorbent than smooth-planed wood. But with sawn timber movement is not critical. A low solids high-penetration woodstain (such as Weathershield Timber Preservative) is more suitable.