Things You'll Need
There are many different types of paint that can be sprayed through an airbrush. Most paints designed for airbrushes do not need to be thinned, and are ready to be sprayed right out of the bottle. Don't let yourself be limited to just those though; there is a huge selection of paints that can be used once they're mixed with thinner/reducer. The thinning process will vary slightly among paint types. Each paint type requires a specific thinner/reducer.
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Choose your paint. Different projects call for different paint, so select the right paint for the job.
Match the thinner/reducer to your paint. Different paints are thinned with different things.
Water colors, Tempera and acrylic paints can usually be thinned with distilled water. Distilled water is preferred because it doesn't contain any of the contaminants that can be found in tap water.
Enamal paints are solvent based, and are generally thinned with mineral spirits.
Lacquer paints are solvent based, and are thinned with lacquer thinner.
Sign paints are also solvent based, but usually require a special thinner/reducer made by the paint manufacturer.
Pour the needed amount of paint into a mixing cup.
Determine the mixing ratio. Most paints will have thinning instructions on the can that include the recommended thinner and thinning ratio.
Add the proper ratio of thinner to the amount of paint in the mixing cup. If the paint you are using does not have any instructions, then thin the paint to a watery consistency. The mixture can be fixed by adding more paint or thinner if needed.
Slowly stir the mixture with a mixing stick until the paint is thoroughly mixed.
Pour the thinned paint through a paint strainer into a second mixing cup. This step is optional, but insures that there is no dirt or debris in the paint.
Using the proper thinner/reducer will make all the difference in the world, so make sure you have all of the needed materials before you start.
Over-thinning the paint can result in running paint with poor coverage. If this happens, just add a little more paint to the mixture to obtain a workable consistency.
Under-thinning the paint will end up clogging the airbrush or spraying heavy coats. Adding a little more thinner/reducer can quickly fix this situation.
Test the mixture on a scrap piece of material before beginning your project.
Follow any manufacture’s safety instructions that may be included with the paint, and use a little common sense. Solvent based paints and thinners/reducers are flammable, so keep them away from open flames. Use solvent based paints in a well ventilated area, and wear a respirator if needed.