It's what's inside that counts. To do a first class airbrush job, a top of the line airbrush is often only as good as the paint it uses. There are different classes of paint that can be used for airbrushing. For the beginner, however, it is best to use paints specially made for airbrushes. These paints have finer pigments than those used for arts and crafts. After some experience with airbrushing, using craft and textile paints should pose no problem. Most have either transparent or opaque colors.
Transparent colors have less pigment and allow the light to pass through enabling you to see different layers on top of each other. They are thinner and can be more easily applied with the airbrush. Transparent colors can also be easily blended.
Opaque colors, on the other hand, prevent light from passing through. An opaque color sprayed on top of another will cover color under it. Opaque colors have more pigment than transparent ones, are thicker and more likely to clog the airbrush tip.
The different types of airbrush paints are watercolors, gouache, acrylics, oil paints and sign paints. Most are available in arts and crafts shops, although some can only be found in specialty stores such as those that sell automotive paint.
Watercolors, as the name implies, are water-based and are ideal for use in an airbrush. They are very transparent and come in tubes or in an already diluted form ready for airbrushing. Water colors are best diluted using distilled water.
Gouache, also known as Tempera, is a more opaque water-based paint. White pigment has been added for opacity, making it slightly harder to use in an airbrush than regular water colors. To dilute gouache, distilled water is also recommended. It should not be allowed to dry in the airbrush and should be cleaned out immediately after it is used.
Acrylics are available as both opaque and transparent paints. They last long on any surface, although some require special preparation of the surface before applying the paint. There are acrylic paints for different materials, such as fabrics, metals or fingernails. Acrylic paints specially made for airbrushes are preferred. They can be diluted with water, or with a thinner supplied by the paint manufacturer. Many acrylic paints require heat setting after application. Like gouache, acrylics should be cleaned out after use and not allowed to dry in the airbrush.
Oil paints are solvent based. They can be diluted with turpentine or mineral oil. Depending upon how much you dilute them oil paints can be either opaque or transparent. It takes a while for oil paints to dry and they can be removed using turpentine or mineral oil as well.
Sign paints are specialty paints which are solvent based. They are intended primarily for use with a special kind of brush to create letters, forms and symbols in the art of sign painting. Care should be taken when using sign paints to wear a mask and to airbrush only in a well-ventilated area.