When painting a house, car or other large project, rollers and brushes just may not do the trick. Paint sprayers save time and energy and can paint, treat and stain up to four times faster than any traditional rolling method. However, even sprayers have their pros and cons, and are classified in two subgroups: air and airless.
Air sprayers are different from airless primarily because they have to be connected to an air supply, which usually means a bulky, expensive air compressor. This connection makes your portability equal to the portability of your air compressor or lengths of high-pressure air hoses. Airless sprayers use pressured streams of paint or stain that do not rely on air flow to force the material out of the sprayer, making them extremely portable. Some models pump directly from the can, which makes them more portable than a typical air sprayer, however, some airless models actually pump from a container of paint attached to the sprayer itself, allowing the sprayer to go anywhere.
When using an air sprayer, a stream of air is forced through the sprayer that pushes the paint out of the sprayer nozzle. This forms a low-pressure spray that is easy to layer but can possibly mix with air and cause paint bubbles or other blemishes in the paint finish. Airless sprayers eliminate the chance of air mixing with paint or sealant and provide a smoother, bolder finish than their counterparts. However, the high-pressure nature of airless sprayers mean that some practice is required to get a proper layering and spraying rhythm to ensure that the paint job does not look uneven or wavy.
The difference in pressure between air and airless sprayers is immense. An air sprayer can only build up to the pressure capabilities of the attached compressor, which generally is within safe operating psi range (psi is a measure of pressure: pounds per square inch). This range is usually safe for breakables like sliding, glass, thin metals and even human skin. Airless sprayers operate by forcing high-pressure paint through a thin nozzle opening that can multiply psi to an unsafe level. The high pressures of an airless sprayer can break glass, knock holes in siding, bend thinner metals and even inject paint into and under human skin.
Air sprayers are much cheaper than standard airless sprayers. Retailing between $20-$100 as of 2010 for new air paint sprayers, the proposition is relatively cheap if you already own an air compressor and the necessary hoses. Airless sprayers can run from around $200 all the way up to $1000, making them a much more expensive alternative. The question of cost then becomes a matter of efficiency: air sprayers are cheaper but take longer to run and can exhibit paint finish flaws, while airless sprayers are vastly more expensive but produce quality work (with practice) in shorter periods of time.
Cleanup is an essential factor in any paint or staining project. Rolling or hand-brushing produces a huge mess that can be eliminated by using either an air or airless sprayer. Both types of sprayers can pump from either cans of paint of from cartridges and both eliminate a lot of the waste and mess from drips and over-spray. However, slopping paint into sprayer canisters carries a risk of multiple minor spills while pumping directly from a can poses the risk of knocking that entire can over.