Different types of household paint
Although paint is a very common material, paint technology is a complicated science. For paint to adhere to a surface, the first coat (normally the 'Primer') must provide a 'key' into the base material (so that paint does not just fall away) and to provide a surface for the other coats.
There are many types of paint available today, some giving different surface finishes, others designed for particular applications. This makes the selection of paint less straightforward, however selecting the correct type of paint will give a more satisfactory end result.
Choosing the correct paint may appear a bit confusing at first, but once you have sorted out which type of paint is for which job and what finishes are available for that particular type of paint, the choice should be fairly easy.
So what is paint ?
Paint consists of pigments and an oil or water-based binder (the binder being the majority in volume). With most paints, long-term storage will cause the two constituents to separate in the can - the pigments generally 'drop out of solution' to form a thick, treacle like sludge at the bottom of the can. For the paint to be usable, the contents of the can must be well stirred (except where the manufacturer says otherwise - as in the case of non-drip paints) to ensure that the pigments and the binder are uniformly mixed. If a stored can is used 'as opened' or even after just shaking, the paint at the top will be mainly 'binder' with very little colour, and by the time the brush reaches the bottom, the 'paint' will be mainly pigment - the whole effect will be from a very wishy-washy colour to a very rich colour.
The proportion of pigment to binder in any paint dictates the amount of gloss the finished product will have. The glossier the finish, the more hardwearing it will generally be. There are various categories of finish: matt, gloss and a range in between the two which varies according to the manufacturer and are designated in a number of different terms - silk, satin, semi-gloss, eggshell etc.
Water-based paint dries purely by evaporation, while oil-based paint has a chemical drying agent added. Paints with a water base are not as hard or durable as those with an oil base although they are improving all the time. The greatest advantage of water-based paint is that brushes and rollers can be washed out in water; no special cleaning agent is needed.
Most proprietary brands of household paints are ready for use as sold and do not, under normal circumstances, require thinning. The general exception is where a thinned first coat is required to seal a surface. Where a can of paint has been opened for a period of time, some of the binder may have evaporated off so thinning of the remaining paint may be needed. When thinning paint, only use the type of thinners recommended by the manufacturer.
The following brief description of types, uses and application should help you to choose the right paint for the right job.
By tradition, gloss paints have been oil-based and include resin to give them a hard wearing quality. Some are still oil (solvent) based paints whilst water based gloss paints are now available.
- Liquid gloss needs an undercoat but gives the more traditional high gloss finish and is extremely hard wearing and resistant to dirt.
- Satinwood is a durable gloss paint that gives a more subtle sheen than the conventional shiny gloss effect, however, it is not usually as hard wearing.
- Eggshell is a paint that gives a flatter (but not entirely matt) finish. It is often used for smaller pieces of decoration such as architrave and skirting.
- Polyurethane gloss an oil-based paint with added polyurethane resin making it tougher, providing a really hard wearing surface to withstand greater abrasion than standard gloss.
- Silthane is a combination of silicone and polyurethane, this paint is claimed to give a stronger surface than polyurethane as the silicone gives extra protection, especially during the drying period when paint is most vulnerable.
An alternative to ordinary gloss, non-drip paint is of a jelly-like consistency and is easier to use if not overloaded onto a brush and adequately 'laid off' on the surface. It is ideal if you have difficulty in painting without drips falling from the brush, as its consistency allows a 'blob' of paint to be picked up by the brush and then applied to the surface where it is spread out normally. Non-drip paint will produce runs if too much paint is applied and not adequately laid-off - this is especially true when painting in corners (such as at the bottom of panels in panel doors).
Manufacturers of non-drip paint often claim that they do not require an undercoat - however a better finish will generally be achieved if an undercoat is used. For exterior wood work, an undercoat is really essential to ensure a good 'weather resisting' finish.
Application of non-drip paints. Take all the normal preparatory precautions according to the surface before applying. Lightly brush out using random strokes and never overbrush as this can cause runs, thus defeating the object of using this type of paint. Do not stir the paint before or during application. The paint may look lumpy and unworkable in the can, but that is the nature of the paint. Stirring will only break down the consistency and ruin the finish. If a can has been stirred, leave it for a while and the paint will become jelly-like again. To strain out dirt particles within non-drip paint, thoroughly stir the paint until it becomes a free-running liquid, strain the paint and then leave it to gel again.
Modern Emulsions are water-based, with vinyl or acrylic resins added to make them more hard-wearing than traditional emulsions. This results in varying degrees of sheen in the finish; as the shine increases, the paint tends to be more hard wearing. The ranges usually offer matt, eggshell, silk, satin and full gloss.
Although normally thought of as for internal walls and ceilings, there are water based types of emulsion specially produced for woodwork. These are easy to apply but do not give the same hard-wearing qualities as oil-based paints.
Interior Walls and Ceilings
Emulsion is the most popular paint for walls and ceilings due to the fact that it is water based and has less smell, dries comparatively quickly and is easy to apply.
There are three main types of emulsion used for walls and ceilings, each giving a different finish:
- Vinyl matt emulsion gives a matt, non-shiny finish that is good for not showing small imperfections on the wall or ceiling. (The shinier finishes reflect back more light and highlight any imperfections). Generally speaking, however, it does not wear as well as the glossier emulsions.
- Vinyl satin emulsion gives a subtle soft-sheen finish and is a more durable surface than vinyl matt. It is suitable for areas that might need to be occasionally lightly washed or sponged.
- Vinyl silk emulsion gives a high sheen finish and is the most durable of all the emulsion paints. It is good for rooms that are subject to a lot of moisture i.e. condensation. Some manufactures make specific Kitchen & Bathroom paint which is ideal for areas of high humidity.
Other types of paint
There are other types of paint available for specific jobs. These include:
- Primer - These may be oil or water based and are used to seal unpainted surfaces to prevent covering coats of paint soaking in. The appropriate type of primer should be used for the surface being painted - wood, metal, plaster or tiles. There are some 'all purpose primers' available which are designed for two or more of these surfaces.
- Undercoat - Usually oil-based, undercoat is applied on top of the primer. The undercoat should be of the correct colour to provide the right colour base for the finishing coats.
- Anti-condensation - For use in humid conditions such as in kitchens and bathrooms, this paint ii specially formulated to prevent the surface becoming cold to the touch and therefore less conducive to condensation. It is not a cure for condensation, only a way of reducing its effect on painted surfaces. They often include a fungicide. Normal emulsion paints may be satisfactory in these conditions providing that the level of condensation is not too high.
- Radiator paint - For use on central heating pipes and radiators, it will stand up to the high temperatures without discolouring as other paints are prone to do.
- Fire-retardant - These special paints contain an additive to provide a fire-resistant quality, they do not resist fire completely, but has a greater flame resistance than ordinary paint and will reduce their spread.
- Bituminous - Although often not considered as a paint, bitumen is used where a water proof coating is required. Bitumen does not dry in the normal sense used with paint, it can crack if stressed when frozen and will run (or at least become sticky to the touch) in hot weather. Thick and usually black, bitumen is for areas where high water resistance is needed and appearance is not important - such as on the inside of cast iron guttering and metal cold water tank.
Bitumen is difficult to paint over with conventional paints as the underlying bitumen tends to bleed into the overlaying paint and will move with temperature changes while the covering paint may not be able to stand up to the movement. If there is a need to over paint bitumen, apply a coat of aluminium paint, this will seal the surface to prevent the bitumen bleeding.