There are a number of pitfalls to watch out for when you paint.
Bleeding.
Bleeding usually occurs on exterior surfaces when a stain already on the surface bleeds through the new paint. Inside, too, problems can arise, as when children use crayons or permanent ink on walls. You may paint the area a dozen times, but the marks always bleed through. (Try spraying them with shellac first.)
Blistering.
Blistering occurs when you paint over a surface that is wet. For example, when you are painting outdoors over rotted wood or on a misty day, the moisture gets underneath the surface of the paint and lifts it up. Blistering usually occurs soon after painting. Be sure the surface is dry before you paint.
Chalking and Fading.
Chalking and fading may simply be the result of the aging process of the paint. If it’s excessive, however, it could indicate an underlying water problem. The subsurface could be wet. You will need to dig down into the subsurface to determine where the moisture is coming from and then put up a barrier.
Nail Popping.
This occurs most often on sheet rock where the nail pops up, causing a protrusion in the paint, although it can occur on any surface. It might simply be that the nail was never properly hammered down. However, if rust marks show through, there is moisture in the wood from which the nail protrudes. You will probably have to get into the wall to determine where the moisture is coming from and then resolve the problem.
Wrinkling.
Wrinkling is usually an outdoor problem caused by putting on too much paint or painting on a hot day. Wrinkling can also occur if the previous coat (or primer) was not completely dry. Whatever the cause, you will need to strip the paint off and start over-a good reason to be extra careful!
Paint will get on you no matter how careful you try to be. Rub on a lotion or petroleum jelly before you start. It will help keep the paint from sticking and make cleanup easier.
Dirt is the biggest bugbear of spraying. Nozzles, tubes and liquids should be spotless; soak the parts in thinners and strain your lacquers through a single thickness of nylon stocking. Having carefully prepared your surface, damp all dust and sweep up thoroughly, then disturb it no more.
Practise spraying on a large piece of flat panel until you have a flat fan of spray, which will coat an area 35-45cm (15-18in.) wide with the gun held 20-30cm (8-12in.) from the surface at 90° to it. It is easier to spray a vertical surface than a horizontal one. Wait a minute to see the effect on your test surface, because lacquer takes some time to run if it is going to. Thin it 10 per cent and get the right consistency by timing it through a viscosity cup. The liquid should flow in a continuous stream off the end of a stick held at 45°.
Spraying techniques are illustrated opposite. Never trigger or stop the gun while it is pointing at the surface. Start the spray, and stop it, off the panel at the beginning and end of your strokes. Do internal corners in one smooth movement; external corners should have one stroke each side and one at a 45° angle.
Pre-catalysed lacquers can be de-nibbed with 600 grit wet and dry paper and water, wiped and tack-ragged after 45-60 minutes, and are then ready for recoating. Acid-catalysed lacquers take longer, about three hours on average. Final coats should be steel wool and waxed, or rubbed with burnishing cream.
Damp in the air causes a milky bloom as the lacquer dries. Burnish it with abrasive cream or paste, or if that does not work strip and refinish. Spray will pick up moisture in a cold damp atmosphere and take it to the surface, where it mixes with the lacquer, causing pits and craters in the finish, with the same white bloom. The air must be dry and warm, but if it is too hot it will dry the lacquer too quickly.
Always clean the gun as if it was a surgical instrument. Dismantle it, soak all the parts in thinners and blow thinners through the gun until there is not a trace of lacquer in the spray.
Finally, take elaborate safety precautions. Fine spray vapours are highly volatile, and extremely unpleasant to inhale; always wear a face mask, have a good extraction system, or do the work outside. Just having the windows open is not nearly enough.
Using a spray gun to apply paint can be quicker and easier than other methods and can give a better finish. Some paints – car body finishes, for example – are specially formulated for spraying; other paints can be sprayed provided that they are ‘thinned’ with solvent.
Successful spraying requires a fair degree of skill and knowledge both about the paint you’re applying and the paint spraying equipment itself.
Types of spray gun
There are two main types of spray gun: with separate compressors or airless.
Spray guns with separate compressors
These are the conventional design of spray gun. Originally, they had large compressors plus a bulky ‘receiver’ to balance out fluctuations in pressure. This type of equipment can still be bought (or hired), but the amateur is more likely to be interested in one of the range of smaller guns with separate compressors. The compressor, which is electrically powered, provides a supply of air under pressure to the gun which has a container for the paint. Some of the air passes into the paint container to pressurise the paint; the remainder comes out through the nozzle as a fine stream. When the gun’s trigger is pulled back, a needle valve at the back of the nozzle is opened and the paint passes up from the container past the needle and into the air flow. The paint mixes with the air flow to provide a fine spray from the nozzle. The amount of paint that flows can be controlled by the trigger the further that the trigger is pulled back, the more paint that flows – though in practice the amount is limited by the power of the compressor.
Airless spray guns
These have all their working parts within the gun unit and have no separate compressor. The paint is forced directly out of the gun by a piston which vibrates backwards and forwards, being driven by an electric armature. It requires a considerable pressure to force the paint out of the nozzle and the amount of paint can be varied by adjusting a knob which alters the length of the piston stroke, though this is generally a fiddly operation. Obtaining a very line spray on an airless gun is difficult since the paint has to be pressurised to a certain level to gel any spray at all.
Airless guns are more compact and cheaper than separate compressor guns, but they do have disadvantages:
- the vibration of the piston can make it noisy and uncomfortable to hold
- an airless gun can ‘splutter’ paint when the level in the container is low. This should ruin a nearly completed job and it is not particularly easy to sec when the paint containers are getting empty. (When spray guns with separate compressors gel empty, they simply produce I spray with less and less paint)
- because the paint can come out of a gun at extremely high pressure, there is a danger of ‘injecting’ the skin with paint if you put a finger too close to the nozzle. This is a serious injury as the paint can spread out under the skin. It is difficult to treat, but requires immediate medical treatment it is important to explain to the person who is treating you exactly what has happened. Most high-pressure airless guns have safety cages round the nozzle to prevent this happening.
For bodywork repairs on cars, small aerosol spray paint cans are available. These are used in much the same way as spray guns. Both primers and topcoats are available – it is important to know exactly what colour shade your car is. Although convenient to use, aerosol sprays are an expensive way of covering anything other than small areas.
Aerosols providing polyurethane varnish and gloss paint (plus primers) are also available good for wicker furniture and louvre doors.
Painting is not a difficult art, but there are definitely a number of key things to think about if you want a professional finish. Let’s take a look at them below:
Wash the walls before you start. Don’t just turn up with your paint bucket and brush. Clean the walls with sugar soap before you start unleashing paint everywhere.
Inspect the walls. Check the condition of the walls before you begin. Take a careful note of any dents or cracks. These can be repaired with filler from your hardware store.
Keep the airflow moving. Make sure you paint in a room that has good ventilation. Some paints may contain a number of toxic chemicals which can cause allergic reactions or headaches as a result of prolonged exposure. Due to this, paint manufacturers are now making a considerable effort to reduce these volatile organic compounds in their products.
Label your leftovers. Generally you will always end up with some spare paint at the end of the job. Label this carefully with both the color and the room it was used in. This can be a godsend down the track if repainting is required and you need to color match your previous work.
Never throw away unused paint. In the UK alone, it is estimated that around 56 million litres of paint were thrown away or left unused last year. If the paint is still usable, think about donating it to a local community group or charity. There are many people less fortunate who may have a great use for the paint that you no longer need.