how to chose the airless nozzle for painting the latex / varnish / stains?

If you use an airless paint spray gun to paint the interior of your house, you need to use several different nozzles to complete the task. For example Latex paint / stain and varnish, each have different viscosity. Each one requires a different size nozzle to ensure proper application.
Acrylic/Latex Paints
• When painting a typical wall or room with acrylic or latex paints, a nozzle with a wide-diameter orifice is used. Wide-diameter nozzles spray wide paint patterns, and allows thick acrylic paint to spray evenly, and in thicker coating. The result is being able to paint faster and in high efficiency. Size 515 to 517 nozzle is recommended.

The three digit numbers used to explain a nozzle size refers to the fan width and the orifice size. For example, “515″ nozzle has a fan width of 10 inches and an orifice size of 0.015 inches. The first digit denotes half of the pattern size. So, the 5 equates to 10 inches of fan pattern spray. The second and third digit measure the orifice size in thousandths of an inch. So, the 15 equates to an orifice size of 0.015 inch.
Wiping Stains
• An airless spray gun can be used to spray wiping stains onto wood trim. The nozzle is small in order to reduce overspray. Wiping stain has the consistency of alcohol and is not thick. Using a 409 to 411 nozzle will keep the spray pattern narrow, and allow a smooth spraying of stain onto the wood. If overspray is still a problem, use a 209 nozzle.
Varnish
• Spraying varnish onto stained molding requires a nozzle between wiping stain and latex. Using a 211 to 213 nozzle keeps the flow of varnish narrow to reduce overspray. The nozzle is large enough to prevent thicker varnish from clogging the orifice. If you use hand-mixed varnish or shellac mixed with flakes, a 413 nozzle or larger is recommended to prevent orifice clogging.