Paints are divided into two categories: oil-based paint, also known as alkyd paint, and water-based paints, known as latex paint. Oil based paint uses petroleum-based solvent as its medium, while latex paint uses water as its medium [source: JoePullaroInc]. Until recently, you could only spray with oil-based paints, since they were thinner than latex paint, did not dry so quickly and did not clog the spray gun's nozzle. Latex paints are now made of new synthetic resins, which are compatible with water, have a thinner consistency and are wet enough to be used in a spray gun. Today you can use an airless gun or aerosol can for spray painting with latex paint. However, you still may find that your latex paint is too thick for your spray gun's nozzle and needs thinning. Here's how to thin latex paint so it can be used in a spray gun.

Materials needed:

  • 5-gallon (18.9-liter) bucket
  • Water
  • Funnel

Here's what you do:

  1. Pour the paint into the bucket.
  2. Add ½ cup of water for every gallon of paint.
  3. Mix thoroughly.
  4. Check the thickness by running the paint through a funnel. If it flows freely through the funnel, you know the paint is thinned enough. If the paint is too thick, add an additional ⅛ cup of water per gallon (3.8 liters) of water and mix.

Remember, adding water will change the color of the paint and alter the drying time. The water will also necessitate using more coats of paint to achieve the desired finish [source: Do It Yourself].