Primers and sealers
After the preparation work has been completed, most surfaces will require a preparatory coating to ensure it is stable and sealed: primers and sealers are essential to achieving a high quality finish.
Applied to resinous timber, particularly knots in timber, to prevent the resin in the wood from discolouring the paint. A primer coat should always be applied after the knotting has dried.
A primer seals the pores in porous surfaces such as timber and forms a key (roughness) to produce adequate adhesion for subsequent coatings. Primers are available for specific surfaces or can be all-purpose. However, bare plaster should always be primed with a proprietary primer; alternatively use diluted emulsion mixed to a ratio of 1 part water to 4 parts paint. Primers can be applied using a brush, roller or pad.
Recommended for stained walls, plaster, and areas that have been treated with a bituminous coating or preservative. Primer-sealer contains fine particles of aluminium and forms a barrier over the surface. If the stain is still visible after the first coat has dried a second coat should be applied.
Applied to clean metal before the topcoat, a rust-neutralising primer will protect ferrous and non-ferrous metals from rust.
Problems with mould are recognisable by patches of black, brown or grey spots on the surface and often occur in rooms that are damp or receive little or no sunlight. This problem can easily be remedied with an application of fungicide. When the spores are dead, brush them away and apply another coat of fungicide before painting.
Alternatively, you can use a diluted solution of household bleach mixed to a ratio of 1 part bleach and 3 parts water. Wash the affected area with the solution and then rinse the surface thoroughly.
When applying fungicide or the bleach solution always wear rubber gloves and goggles.
The quality of finish of the topcoat is dependent on the undercoat. An undercoat is a specially formulated paint that increases the opacity (dullness or cloudiness) of the surface. The number of coats needed will vary on the surface you are painting. For instance, if applying undercoat to a very strong base colour then two or even three coats will be needed. Always use pale undercoats under a pale topcoat and a dark undercoat if you are planning to use a dark topcoat. It can be applied with a brush, roller or pad – all of which can be cleaned with white spirit.
There are basically three types of topcoat paint: emulsion, eggshell and gloss. However, gloss and eggshell paints are also available as non-drip paints.
An extremely versatile, water-based paint normally used for decorating walls and ceilings. Emulsion is available in several types of finish, the most common being matt and silk. Standard emulsion should only be used for interior work and can be applied with a brush, roller, pad or paint sprayer (if using a sprayer the emulsion will have to be diluted with10% water).
Emulsion paint dries quickly and does not leave brush marks. Painting tools should be cleaned immediately after use with water and detergent. The problem of re-painting white walls or ceilings is seeing whether you have covered the surface evenly. This is easily overcome by using a colour-fugitive emulsion, which appears pink when being applied but in less than an hour dries to a brilliant white.
Eggshell paint is also known as semi-gloss, silk, satin and sheen. It can be either water or oil-based and has a slight sheen finish. It is normally used on interior wood surfaces but can be used on walls if a hardwearing finish is required. Two coats will probably be sufficient to give a good finish. If using an oil-based eggshell paint the brush, roller or pad will have to be cleaned with white spirit. A water-based eggshell paint can be cleaned with water and detergent.
This can be either water-base or oil-based paint and is used mostly to paint wood and metal. Satin paint is similar to gloss paint but have slightly less of a sheen. The water-based version is easy to apply and will not yellow with age, but is not as hardwearing as oil-based satin paint. Satin paint is suitable for both interior and exterior use.
A hardwearing paint with a high level of light reflection, gloss paint can also be water or oil-based. But although water-based gloss is easier to apply and does not yellow with age, it is not as hardwearing nor does it produce the shine of an oil-based gloss. Gloss paint can be used on wood and metal, inside or out, and one coat on top of an undercoat is usually sufficient to produce a quality finish.
Whether using gloss or eggshell paint the best finish is achieved when applied with a brush, which should be cleaned in white spirit if using an oil-based paint, or water and detergent if using a water-based paint.
This type of paint has a jelly-like consistency and is easier to use if the brush is not overloaded. It is excellent if you have difficulty painting without dripping paint from the brush. But care still needs to be taken when using non-drip paint, as runs can occur if too much paint is applied and not adequately laid-off.
Acrylic matt paint
A quick drying, water based-paint that resists cracking and peeling. Avoid applying in damp or humid conditions, as the paint will not dry satisfactorily.
Both eggshell and gloss paints can be non-drip. This type of paint has a jelly-like consistency and is easier to use if the brush is not overloaded. It is excellent if you have difficulty painting without dripping paint from the brush. But care still needs to be taken when using non-drip paint, as runs can occur if too much paint is applied and not adequately laid-off. Manufacturers’ claim that non-drip paint can be applied without an undercoat and still produce a good finish. But for the best finish it is always advisable to apply an undercoat.
This type of paint has been developed for walls and ceilings that have uneven or unsightly surfaces. It is much thicker than ordinary paint and forms a thick coating on the wall or ceiling which is very difficult to remove. Textured paint should be applied with a shaggy roller unless the manufacturer recommends otherwise. Tools should be cleaned with white spirit.
Generally used on rendered or pebbledash exterior walls, masonry paints can be smooth or textured. Smooth masonry paints cover a wider area than textured masonry paints. But textured paint is ideal for covering up minor imperfections such as hairline cracks up to 2mm (1/16 in). Masonry paints can be applied using a brush, roller or spray gun.
Masonry paintbrushes should be 100mm-150mm (4in-6in) wide with coarse bristles. Apply the paint to the wall with vertical strokes followed by horizontal strokes. On very rough textured walls a banister brush can be used.
There is also a reinforced masonry paint which has a fine powdered aggregate added to produce an extremely weatherproof textured finish.
Generally used as an exterior paint for protecting metal gates, guttering and pipes etc. Proprietary brands have been developed that you can paint directly onto rusty surfaces without first applying a primer or undercoat, though the surface should always be cleaned down with a wire brush or wet-and-dry abrasive paper.
Cement paint comes in the form of pigmented dry powder to which water is added. It is one of the cheapest options for exterior painting. Porous surfaces should be sprayed with water, and then have two coats of paint applied. Mixing instructions should come with the product, but as a rough guide 2 parts powder to1 part water should be mixed in a bucket until a smooth, creamy consistency is achieved. Cement paint will begin to dry after an hour, so only mix up the quantity of paint you will be able to use in that time.
Solar reflective paint
This is a bituminous, aluminium paint suitable for the protection of steel, asphalt and bituminous roof coverings. Solar reflective paint as its name suggests will reflect the sun’s heat, reducing the build up of heat in the rooms below. This type of paint is quick drying and only requires one coat.
A radiator bleed valve is situated on one side at the top of the radiator. The valve is loosened with a special key.
Black and viscous, a general-purpose bitumen paint is waterproof, weatherproof and corrosion resistant and suitable for iron, steel and concrete.