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SPRAY PAINTING For quick and efficient decorating you can't beat a spray gun. Here's how to get the best out of these easily operated labour-saving units
By Ray Lewhite.

Spray painting with a gun isn't that difficult, though the average decorator often fights shy of it. Perhaps he is thinking in terms of the expensive and complicated compressor plant used commercially. But smaller units are made. They are reasonable in price and do good work. Compressor plant used by the big contractors is designed to run for long periods under adverse conditions. The air supply can be varied at will to suit the materials being used.
Air is compressed by a small electric motor or petrol engine and stored in a pressure chamber connected to the gun.
The decorator who really needs a compressor plant can get a small portable unit from the hire shop. It will handle everything he wants it to do.
It is most likely though that the decorator with only a comparatively small amount of work to do will prefer to invest in a self contained spray unit. These can be easily bought and are priced quiet reasonably.

Air volume units

Spray Painting
They rely on a constant stream of air supplied by a fan or something similar and have no pressure controls. It is therefore necessary to adjust the material used by thinning, though some manufacturers get over the difficulty by supplying different-sized jets or gravity containers.
These types are known as air-volume units. They work on the scent spray principle. While it is nearly always necessary to thin material for spray work, air volume units require a much lighter bodied paint than the compressor types. Care must be taken not to over-thin or there will be a loss of 'blinding' power and a great number of coats will be required.
When the paint is down to the correct consistency it will be ejected as a fine mist without blobs or splutter. You will be able to use a thicker mixture in a portable compressor unit and obtain a good 'blinding' coat at one application. The pressure required from the compressor depends on the type of gun in use and the air delivery available. Follow the instructions with your unit. If these are not available with a second hand unit write to the manufacturers and they will put you right.
Practice on some scrap wood before you attempt your first job. It won't take long to get the feel of the gun. Control of finger movement is very necessary so that the spray action is started at the commencement of the stroke and cut off at the join-up with the previous application. This should be done with a slight overlap not greater than half the spray pattern to ensure a perfect blending without any sign of join.
Hold the gun at right angles to the work and always keep it the same distance away. Don't swing it in a sweep from the elbow : this will give a patchy finish for too much paint will be applied when the gun is nearest the work. Move the gun evenly without jerky strokes. Aim for a even coating. Too slow a movement will lead to runs ; too fast will mean not enough paint is deposited and you will have to apply another coat. A jerky movement will produce an uneven coating.
As a good rule keep the gun about 6 to 8 inches from the work. If it is too near a lot of surplus paint will be deposited and you will have to increase the speed of movement to prevent sagging. If the gun is too far away you will get dry spray and excessive spray dust which in turn will cause a sandy finish.
When using a gun the centre of the spray pattern receives more paint than the outside edges. This lighter spray at the centre edges is known as over-spray and will vary with the material used and the distance the gun is held from the work.
Because of over-spray it is impossible to paint a sharp edge unless you shield the work with a piece of metal held over the surface not to be painted. Or you can use masking tape stuck on the work.
Window glass can be shielded with tape. A very slight margin should be left between the tape and the wood to allow the paint to lap on the glass and help prevent moisture seeping into the wood through condensation after rain.
When spraying skirtings, the walls and floors can be covered with newspapers held in place by tape. Run tape along the edge being sprayed to give a sharp edge. Masking need not be removed until all work has been completed and is quiet dry or the sharp cut edge will suffer.
A piece of metal 24in.x 8in. makes a useful shield. It will be found handy when spraying a wall where it meets the ceiling. In many cases it can be used instead of masking tape and will save a lot of time in shielding preparation.

Spraying mouldings

Spray Painting
Woodwork consisting of moulding with deep hollows should be first given a light mist coat by moving the gun slightly faster than normal and keeping it a little further away. This will give better coverage in the hollows and avoid paint building up on the high spots and producing runs. A second application should be sufficient to give perfect coverage.
Large areas such as walls and ceilings, can be sprayed at great speed and there is a welcome absence of brush marks. Work away from the light, completing the bed of the ceiling first followed by the cornice and frieze.
The sequence of working with a gun does not really differ from brush techniques : for doors, spray moulding and panels followed by rails and stiles, from the top down. Don't attempt too much at one coat. The speed of spray work will allow ample time for an extra coat.
When working out of doors it is advisable to choose a day with little or no wind or the over-spray will be difficult to control even with a shield.
Preparation for work follows the same lines as when using a brush. Spray painting gives no short cuts as far as preparation is concerned in fact you should take extra care to fill all cracks and smooth down well. A sprayed coat is very even and will show scamped preparation more easily than brush work.

Priming coat

Spray Painting
Some people consider it good practice when painting new wood for the first time to give the priming coat by brush. This does allow a heavy-bodied coat to be applied in one go and so feeds the wood to a greater extent. This is really a matter of opinion which is debatable between spray and brush enthusiasts. An interesting technique when spraying a wall is to blend a dark colour into a light background. This is done by applying a solid darker coating above the skirting board, gradually increasing the distance between the gun and the wall as you go up. You finally reach a mist coat at breast level.
Shadow patterns in odd shapes can be achieved by cutting out the patterns from cardboard or stiff paper. Hold them against the wall and lightly spray around the edged. The over-spray leaves an outline on the background when the pattern is removed.
You can have a lot of fun trying out these ideas. They will give your work a really professional look. Choose your colours and patterns carefully. Any mistake can always be rectified by going over with a coat of the background colour.

Spray Painting
Renovation of furniture, particularly basketwork article can never be really well done with a brush. But spray can bring them back to new. Two colour work gives an exellent effect on basket work. Spray on a solid ground coat in the appropiate colour. Then mist spray a contrasting colour around the edges and corners, picking out some feature points with a solid spot.
Colour combinations are many but the metalics are good for the contrast mist spray. Here are just two : blue ground coat with a silver mist, and green with gold or bronze mist finish. Metallic powders are obtainable with their liquid media and should be mixed just before application or the colour will go dull. They are off very light body and any type of gun will handle them ; i have even seen them applied with an ordinary fly spray.

Tables

Spray Painting
When spraying a level surface, such as a table top, start at the nearside and work over to the far edges. This is essential when using quick drying material such as French polish or cellulose, since over-spray falling on wet work will dry with a sandy finish.
It may be necessary to tilt the gun a little, but whenever possible try to tilt the work instead so that the gun is kept at right angles to it. From the edges of the table use a 'banding' technique. One stroke along each edge will coat the edges and 'band' the face at the same time. Then you can continue by spraying the centre as already mentioned.
When painting an inside corner, in a cupboard or on a wall, do not spray direct into the corner. This will give an uneven coating. It is better to spray each side of the corner separately.
You will probably want to use your spray gun when creosoting garden fences. It can be a long and dirty job but providing you choose a windless day your gun will speed up the work tremendously. To cover an open work fence hold the gun at an angle which will include the edge and face in one up and down stroke. This will save material and time.

Now you will want to know something about the types of material you can use in your gun. And I suggest that, if you are a beginner, you start with oil bound washable water paint. This is easily handled by practically any outfit and can be thinned by the addition of water or petrifying liquid. I prefer petrifying liquid myself, as this gives a smoother finish and checks surface porosity. Plastic emulsion paints are not so good for the smaller outfits as they cannot be thinned satisfactorily and they tend to block the jets by rapid drying out while in the air stream. Leave emulsion paints for the larger types of compressor plant, which can handle them with ease.
Alkyd-resin-based paints have proved most satisfactory for the type of outfit used by home decorators. Thin according to the makers instructions : turps or white spirit is normally used but some brands require special thinners. Manufacturers do supply paint ready thinned but the air-volume type of unit will still require this to be thinned down again. Remember that the air-volume unit requires a very light bodied material.
For varnishing, cellulose lacquer is most suitable in the light units. Cellulose products should never be applied over ordinary paintwork as the solvent will probably destroy the paint. Thin cellulose with special thinners (and nothing else) and you will find it an excellent material for spray work.
If you are using cellulose enamel your stopping, primers, undercoats, thinners, and enamel finishes must all be cellulose products, preferably from the same manufacturer. Large scale spraying of cellulose needs a different technique from ordinary home decorating and the spray painting of motor cars for instance, makes a complete subject in itself.
Sealer primers and damp wall solutions can always be obtained ready for spray work. French polishes, button polishes, and knotting will normally spray without much adjustment but should they be of an age to require thinning, methylated spirits is the medium to use.
Undercoating primers, and flat paints can all be thinned without much trouble and application is easy and rapid. The latest types of non-drip jelled paint are obviously not suitable for spraying.
You should experience very little trouble with your first venture into spray painting. But here are some final tips to ensure your success.
Spray Painting
Know your gun and follow the makers instructions. Above all, keep it free from dirt. The slightest speck of dirt may cause a blockage in the jets and force you to strip down completely in the middle of a job.
Strain all paint (through an old silk stocking for instance) into the container attached to the gun at time of filling.
A break in working even for fifteen minutes, should only be taken after the gun has been cleaned thoroughly by spraying thinners. Have a second container half-filled with thinners always by you.
When you have a break remove the paint container from the gun, substitute the thinners container and spray a good quantity of thinners into an old rag. Leave the thinners container connected to the gun and spray again before changing back to the paint container : Always keep the lid on the spare container when not in use.
Always make adequate preparation of your surfaces before starting work. Spray painting does not allow you to skimp this preparation. But after a little practice you will find the speed of application still enables you to do a quicker job.


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