Most paints require stirring before use, but read the instructions, particularly if the colour appears even when you open the can.
Some oil paints need a very thorough mixing, using a clean wooden stick. Varnishes are better not stirred violently as this causes air bubbles which will mark the surface. Do all stirring before use, otherwise the colour may be affected.
Starting from a bare surface, the first paint is a priming coat. There are special primers, which penetrate wood and grip the grain. For metal, a primer has constituents that bond to the surface. The next coat is undercoat, Both this and the primer finish with a matt surface. In some painting systems the primer is made by thinning undercoat. The colour of the undercoat is complementary to the colour of the top coat, although not necessarily the same. A slightly different shade allows progress of the top coat to be seen more easily. If there has to be any build-up to get a sufficient covering, this is better done with several undercoats than by repeating the top coat, which may run if glossy paint is used. Normally, each coat has to dry and should be rubbed down before the next coat, but there are some synthetics where following coats have to be applied within a specified time.
It is helpful to hang a wire across the centre of a paint can, so the brush can be wiped against that instead of the edge of the can, where drips will soon run down the outside. So far as possible, only dip about 50 per cent of the depth of the bristles into the paint, because as work progresses, particularly overhead, paint will soon drip back into the brush.
How much brushing to give depends on the paint. Some paints have to be applied with minimum brushing. If no limitations are mentioned in the instructions, dip the brush, wipe off some of the paint, then apply it to the surface, first crossing in at least two directions to spread the coat. Finish with strokes in the direction of the grain or the long way of the piece. As subsequent parts of that surface are painted, make the finishing strokes back towards the previously painted part, lifting the brush as it goes over the edge of that part. In that way, brush marks in the finished surface will be avoided.
If you are painting a vertical surface, you may have to brush across if it is wide and shallow, but if possible finish with up and down strokes. Start at the top, so later painting comes below and the final strokes are upwards. There is then less risk of ‘runs’, where excess paint forms into lumps as it slides down slightly. However, if brushing is in several directions before the final strokes there is little risk of this happening. If a run or sag occurs, let it dry, then sand it level and paint over. On the top coat, try and brush it out while the paint is still wet.
When dealing with panels in a door or elsewhere, paint the panels first. Get well into the surrounding angles, but be careful not to have too much paint on the brush, or it will build up in the angles or corners and may run. When dealing with windows, paint the bars and the mouldings before the wider parts of the frame. In other structures, it is normally best to deal with narrow parts before broad.
If there are two colours to be used on one piece, it is usually better to apply the lighter colour first. If it runs over to where the darker colour will come, the darker shade will hide the lighter one. Masking tape can be used to define the edge of the second colour. With some paints that set very hard, leave the tape until the paint is almost dry, then peel it off. If you wait until the paint is very hard, you may finish with a cracked line.
When using a roller for walls and ceilings, have enough paint in the tray and work the roller up and down the slope of the tray. A little experience will show how much paint to take up or work out to allow satisfactory use. A roller covers large areas quickly, but is unsatisfactory where edges have to be defined. Use a brush around edges. When dealing with a wall or ceiling, use the brush at the edges, doing small areas at a time ahead of the roller so that both coats are liquid when they meet. If all the edges are done first with a brush, the paint may be dry before the roller reaches it and the meet may be obvious.
For the same reason try to use the roller in such a way that it always meets a previously wetted surface and not one that has dried, although on a large area this is not always possible. Distemper and emulsion paint can be rolled in all directions and they should dry without marks.
For outside work the techniques are very similar, but the main problems are those of access and weather conditions. You have to use ladders and may only be able to reach a limited area at a time. Scaffolding makes working easier, but is a complication. Wood and metal are painted as already described. If stone, brick or cement are to be painted for the first time, use a special sealer (the builders’ merchant can advise). This prevents efflorescence, which is the working through of salts in the wall, to show as white deposits on the new surface. It is essential, however, to prepare the surface in accordance with the manufacturer’s instructions. Follow this with cement paint, usually two coats. One coat may be all that is needed over an old painted surface.
It is possible to use exterior-grade gloss oil paint on stone or brick. Seal a new surface and apply an undercoat. If the lower colour shows through, apply another coat before the top coat. There are exterior grades of emulsion paint which can be used in a similar way.