Painting Wood



Painting Wood

There are many sections of your home that are made or finished in wood – windows, doors and the trim pieces, both inside and outside the house. Every few years they need to be painted to protect the wood and to give you the lovely finish that paint can provide.

On unpainted wood Prime, undercoat and two topcoats is the general standard and on wood that’s been painted before – sand the surface, fill cracks or holes and apply two topcoats, being careful to determine whether the previous coats were oil, or water based – you can’t paint water based paint onto an old oil paint.

On new woods ensure that the wood is smooth and free of dirt or rosins and that all holes have been filled. The first painting step is to apply a primer. The primer contains linseed oils and other properties that soak into the wood, seal the pores in the surface and keep the wood moist so that it won’t crack over time, especially when in direct sunlight. One coat of primer is sufficient and 16 hours drying time is a general recommendation, but check your manufacturers requirements on the back of the can.

Now, if your woods have been painted before you don’t need to prime them again.

If the existing coat was with a water based paint, you can skip the next step, which is undercoating, but if your existing coat was oil based, you’ll need to apply an undercoat.

To test rub some meths onto the paint surface. If paint comes away on your cloth the coating is oil based, if you don’t see any paint on the cloth, the surface is water based.

The primer often lifts the grain of the wood. A very light sanding with 220 grit sandpaper will remove any roughness. This is known as de-nibbing.

Next apply an undercoat. Undercoats stick to anything. The undercoat will adhere to the surface of  an oil based primer and a water based topcoat can be applied on top of the undercoat. The undercoat will attract the molecules of the topcoat, very much like velcro, to create a very strong bond.

Undercoats are available with both oil and water bases, ask your paint specialist for a recommendation for the type of wood that you’re painting.

Water based paints are becoming more popular these days. They’re environmentally friendly, easy to apply and easy to clean, you just rinse your brush and roller covers in water, you don’t have to use turps at all. And drying time is around 2 hours as opposed to the 16 hours needed for oil based products.

There is a big move toward producing most paints in water based versions these days.

Once again sand the wood very lightly to denib the surface and remove the dust from the surface of the wood before applying the topcoat.

If you use an eggshell or gloss enamel, an undercoat is necessary. However if you use a product that contains an undercoat, the undercoat  process can be skipped. This will save you a lot of work and quite a bit of money too, as you’re cutting out a quarter of the work and buying less product.

Sand previously painted surfaces with 220 to a prepare them for the topcoat and fill cracks and holes. The wood will expand in hot weather and contract in the cold, so use a filler which is able to stretch and flex.

Apply the topcoat with a brush or roller. Large surfaces can be covered more quickly with a roller. A roller cover with a 5mm nap will leave a smooth finish. Sponge roller covers often work well, but can leave bubbles with certain paints. The smaller rollers can be very useful for wooden surfaces to get into areas that would not be practical for a large roller. Try a few roller covers and you’ll soon find one that suits your needs.

It’s important to apply two topcoats. It’s better to apply two thin coats than one thick coat and with two topcoats your wood will be properly protected for many years.

Well that’s it, Prime, undercoat and two topcoats is the general standard for previously unpainted wood and on wood that’s been painted before – two topcoats if using a self-priming topcoat. Chat to your paint expert if you have any queries. We’ll cover staining and varnishing woods in another programme.