Overlapping Strokes: the Keystone of Spray Gun Success

A complex combination of air pressure, paint viscosity, surface preparation, painting speed, positioning of the spray gun relative to the surface, and the painter’s gait and steadiness of hand are all involved in producing a smooth, even, glistening paint job when the car is finally rolled triumphantly out of the garage or spray booth. However, all these other factors are rendered completely null and void if one particular detail is not attended to – the need to overlap your strokes.

Regardless of whether strokes are applied horizontally (which the vast majority are) or vertically, proper paint coverage can only be guaranteed if the strokes are sufficiently overlapped. The general rule is to overlap each stroke by 50% with the one before, with the obvious exception to this being the first stroke – which should be overlapped by 50% onto the masking paper alongside the painted area, or off into space if needs be.

The method of making an overlap of this amount is simple and straightforward. Aim the center of the air cap at the bottom edge of the previous stroke, which means half of the paint will fall above this line, and half will fall below. Remember that if this is done with a 4” spray pattern, the paint will advance by 2” every stroke, while a 6” spray pattern will advance the paint edge by 3” per stroke.

The pattern of making strokes is similar to plowing a field – a stroke is made in one direction, and then the return stroke is made in the exact opposite direction. The strokes should be made from top to bottom of the vehicle whenever they are made on a vertical or slanted surface, since droplets of paint will spatter downwards, drawn by gravity, and could spoil a paint job were the strokes to be made from bottom to top.

If you are painting vertically, start at the edge nearest the air filtration system inlet. Make certain that the car is positioned to allow you to paint from left to right if vertical strokes are being used for whatever reason, assuming that, like around 85% of the population, you are right-handed. Left-handed painters will find it easier to paint from right to left instead.

The method of spraying from top to bottom matches human perceptions and proportions closely – you can see the edge of the paint to aim for to achieve overlap much more easily, for example, since your head is positioned above the spray gun – and is likewise preferred for this reason.