Thursday, September 16, 2010

Equipment and facilities

There are three types of equipment which could be considered suitable for painting cars. Small electric sprayers have a very low output and although they might prove ideal for re-touching a small area of
damaged paint, they will prove inadequate for spraying whole cars or even whole body panels. The recently introduced warm air sprayers offer a high volume of low pressure air, and are claimed to reduce paint wastage (high pressure compressed air wastes a lot of paint in the atmosphere) and give good results. Unfortunately, no example was made available for testing whilst this book was being prepared.The traditional equipment consists of an air compressor and spray gun. Air compressors for spraying range from tiny units which have so short a duty cycle (the period of continuous operation) that a roof panel might have to be sprayed in two goes, to giant floor standing units with huge air tanks. In between there are a number of compressors which are popular with DIY restorers. The minimum acceptable compressor for serious work would have a litre air tank, although 50 litres is far better and a 100 litre tank would be by far the best option. Small air tanks rapidly run out of 'puff' when the air pressure drops and this has to be
replenished by the air pump. This places warmed air into the tank, which can dry the paint in the air before it ever reaches the panel!
In addition to the compressor, you will need at least one and preferably two water/oil traps for the outlet connection, When air is compressed, water droplets form in the tank and can be blown through the spray gun to mix with your paint and ruin the painted finish. Also, tiny droplets of oil from the pump will contaminate the air within the cylinder, and both this and the water will have to be filtered out before the air reaches the paint gun.
Most spray guns work rather like a carburettor, because as air is forced past a jet of sorts at high velocities (and hence at low pressure) paint is drawn up to mix with the air in exactly the same way that petrol mixes with air in a carburettor. Other guns have a gravity paint feed and are characterised, not unsurprisingly, by the paint container being mounted on top of the gun. You should buy the best spray gun and compressor that you can or alternatively,hire them.
You will also need a mask, Paint which dries in the air forms a fine dust which you should avoid breathing in, and because the fumes from thinners are also to be avoided, a respiratory mask is needed rather than a simple dust mask which cannot provide sufficient protection.
It is possible to spray a car out of doors given favourable conditions. The weather should not be too hot nor too cold, it must not be wet or windy. A still day is essential, and the temperature should be somewhere in the range 10-20 degree C. A warmer day may appear a better prospect, but warmer days see greater activity from winged insects, which appear to be fatally attracted to wet paint! However, it is far better to apply paint indoors if this is possible, because it allows you some control over the conditions.
The paint should be applied in a clean dry atmosphere which has reasonable ventilation. The corner of the workshop in which you recently rubbed down bodyfiller is no place for paint spraying unless it is scrupulously cleaned firstly. The floor should also be lightly damped down with water to prevent dust from being kicked into the atmosphere by your own movements. You will require good, even lighting so that you can see which areas you have covered and which you have not.
The temperature and humidity at the time of spraying are important factors. If the temperature is too high, much of the paint can dry in the air before it ever reaches the panel, giving what is known as 'dry spray'. If the humidity is too high then water contamination will be apparent as 'bloom'. The surface will be very dull. Avoid very windy days if your workshop has a lot of ventilation.

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