FAQs:  How Much Paint Do I Need?

1. COLOR & PIGMENTATION: To achieve good coverage of a color the first factor is the color of the substrate on top of what you're painting.  For example, if you're painting a white color on top of a red primer, chances are it'll take twice as much white paint to cover up the red color underneath--black is the worst color to cover up, unless of coarse you're painting back over it with a dark dark color.  Once you have a compatible substrate color (neutral colors like light grays and beiges are the easiest to cover) than coverage depends on the pigmentation in the color you're spray.  Yellows, greens and blues tend not to cover as quickly as blacks, reds and whites.  Also, a consideration is what the pigmentation is made out of--polyester's (BASF's Diamont, Glasurit and Sikkens) cover twice as good as traditional enamel based technologies (Dupont, PPG, Sherwin-Williams, & Martin-Senior). 

2.  SPRAY EQUIPMENT:  Older siphon feed guns (non-HVLP) have the least amount of transfer efficiency--meaning 30% of the material you're spraying reaches the surface and 70% becomes overspray in the air (which can eventually settle with disastrous effects without good airflow over the surface being painted).  A High-Volume-Low-Pressure gun (most a gravity feed) has just the opposite transfer efficiency--that being 70% of the material reaches the surface and 30% floats into the air as overspray.  Most square footage calculations are done with HVLP equipment being considered---therefore, if you're not using HVLP, be sure and take the need for more material into consideration.  

3.  REDUCTION & ADDITIVES: Most basecoats are either a 2:1 or 1:1 reduction (2 parts color to 1 part reducer).  Therefore if the reduction is 1:1, then 2 quarts of color mixed with 2 quarts of reducer would yield 1 RTS (Ready-To-Spray) gallon of paint.  A basecoat can be reduced less to achieve better coverage, but the potential for dry spray and the results yielding a rougher texture is more likely.  Now a days, most of the major paint manufacturers are providing and even recommending the use of a hardener in the basecoat.  If you chose to add a hardener into the basecoat (obvisiouly, increase the amount of RTS material) this too will increase the coverage of your color by about 10%.

The general rule of thumb then is . . .

For a small - medium size vehicle (less than 150 sq ft. of surface that needs to be painted) than 2 quarts of color is how much material you'll need (and 2 quarts of reducer) or 1 ready to spray gallon.

For a large vehicle or truck (including door jambs but NOT inside the truck bed) than 1 gallon of color or 2 ready to spray gallons is how much material you'll need.

One more consideration when determining how much paint you'll need--if you're doing a complete color change and plan on spraying under the hood, deck lid, door jambs and any other nook or cranny, but sure and order at least an extra quart or pint of color since these places are more difficult to spray and you tend to waste more materials trying to cover them up.