A spray gun can turn a stain or top coat into a fine mist – a process called atomization which propels the mist onto a work surface. Compared to rags and brushes, spray guns transfer liquids faster and leave a more level surface. Air from a compressor or turbine enters the gun through the air inlet at the bottom of the handle. When you pull the trigger just a little, the air valve inside the handle opens and allows air to flow through the gun. Pulling the trigger farther retracts the fluid needle, which allows liquid material to stream out the fluid nozzle. The result is an atomized fluid stream in a shape varying from circular to an oval fan pattern.