Practical Applications For Airbrushing


What is an airbrush?

There are three main types of airbrushes: dual-action internal mix; single-action internal mix; and single-action external mix. There are other variations of these same three types that have evolved in recent history, but they basically work in the same way as one of these three types.

"Dual-action" refers to the way in which an airbrush is triggered (press down for air, and back for color). This allows you to change the amount of paint that comes out of the tip without stopping to adjust the brush each time.

When a "single-action" brush is triggered a pre-set amount of paint is sprayed. The amount of paint can be adjusted by turning the adjustment screw at the back of the handle.

"Internal mix" and "external mix" is the method by which the paint and the air come together. The "internal mix" brush produces a much smaller dot pattern than the "external mix" airbrush.

Note: the external mix airbrush usually will meet the needs of most model railroaders, and is less costly as well.

Why airbrush?

An airbrush allows a much more natural looking, smooth finish than you could get with a conventional paintbrush.

When should you use an airbrush?

An airbrush can be used in so many ways that it would be hard to say just exactly when to use one. It can be used to paint your scenery backdrop, locomotives and rolling stock, track, or it could be used to paint structures. It can also be used to weather various parts of your railroad with a much more natural look than can be achieved with a conventional brush.

If you are airbrushing a structure or other model, it is usually best to air - brush individual components such as window frames or other small parts before assembly. Once the model has been assembled it can be weathered for a more natural effect.

How to airbrush?

One of the most important steps in airbrushing anything, is surface preparation. Most plastic and metal has oil or mold release on the surface from the manufacturing process. This needs to be removed. The best way to remove these substances is with a mild dishwashing detergent and water. After soaking the item for a few minutes use a toothbrush to scrub the surface, and then rinse thoroughly with fresh water. Shake off the excess water and then let the item air dry.

You will need to have an air source for your airbrush before you begin. An air compressor is usually best. There also needs to be a filter and moisture trap between your compressor and your airbrush. This is especially important if you want a fine smooth finish. Alternative air sources such as a spare tire, with the proper adapter, a portable air storage tank, or a can of compressed air will work for small jobs.

If you use a compressor, you will need a 1/4 inch pipe adapter. When you are using a non tank mounted diaphragm type air compressor you will need to drill a small bleeder hole in the adapter with a 1/32 or a 72-inch drill bit through the flat surface, just past the taper on the adapter.

With the exception of some of the new acrylic paints such as ACU flex and model flex, most paints are too thick to spray without thinning. You should always follow the manufacturer’s recommendations when thinning paints.

If you are using a lacquer or enamel based paint, be sure to use the thinner from the same manufacturer for that purpose. Using anything but the correct thinner could affect the quality of the paint. You can, however, use any lacquer thinner for clean up. This will be less expensive than the thinner.

You need good ventilation when spraying most all paints. Be particularly careful with lacquer or enamel based paints. They are quite flammable so the proper precautions need to be taken to safeguard against fire or explosion hazards.

The size nozzle and the pressure you use will depend on the type of paint you are using. A medium nozzle will work well for most modeling applications. Generally you will need a medium or course nozzle for the thicker paints such as water base paint or acrylics. The pressure will vary as well with a higher pressure being used for the thicker water based paints, and a lower pressure for the thinner lacquer base paints.

A pressure range of 10 - 15 lbs. works pretty well for lacquer or enamel, and between 15 - 30 lbs. for water based paints. You will have to experiment with each paint to find the right pressure.

Keep an extra jar of thinner handy to run through the airbrush to clean the nozzle between different colors, or when putting the airbrush down for a while.

Fill the paint jar 2/3 full or less and attach to the airbrush. Use a newspaper or other surface to test the airbrush before you attempt to paint your model.

Mask areas that you do not want to be painted before you start with photo frisket or masking tape. A piece of acetate or cardboard can also be used as a mask on flat surfaces. For sharp lines, hold the mask against the surface. For soft edges, hold the mask away from the surface slightly with a ruler or other material.

For more advanced airbrushing jobs where two or more colors are being applied, you will need to mask off areas that you don't want painted. Start with the lightest color and continue with progressively darker colors.

Make certain that each color has time to dry completely before you mask on a freshly painted surface. If you use your fingers to take some of the tackiness away from your masking tape before you apply it you will have less problems with the masking tape sticking to the paint or pulling any of the fresh paint off. To help prevent the fresh paint from coming off with the tape, never leave masking tape on for more than just long enough to complete the paint job.

The masking tape should be cut with a razor blade or sharp hobby knife in order to give a nice crisp line to your paint. Cut it on a piece of glass or other hard surface.

Burnish the tape down with your fingernail along the area to be masked being careful to work the tape around any detail or irregular surfaces.

After the painting has been completed remove the tape slowly by pulling it up and away from the fresh paint at a sharp angle to the surface.

Hold the airbrush about six or more inches from your work and move it back and forth parallel to the surface as you paint. Start moving the airbrush before you press the trigger and follow through after you release the trigger.

Overlap each pass slightly, but be careful not to get too much paint on at once. It would be better to apply several coats to get the coverage you want, allowing the paint to dry slightly between each coat. The paint should reach the surface appearing wet and dry rather quickly.

Practical applications
painting structures, locomotives, and rolling stock, is a very important step of model railroading. It hides the plastic surface and gives you a good foundation for further weathering. Try and paint as many of the various parts as possible before assembly. Windows and doors, shutters, the roof, etc.

One interesting technique is to simulate peeling paint. To do this first use a wood colored stain, metal color or whatever color the surface of the original piece would be under the paint. Then rub rubber cement on areas you want the peeling paint effect. Next apply the finish coat of paint. When the paint dries, rub the surface gently and some of the paint will peel off where the rubber cement had been.

Next assemble the building and add water stains under windows and on the roof. Also add rust stains where metal parts may leave their telltale signs of rust.

You can also use your airbrush while laying track. First load your airbrush with rust colored paint. Spray both sides of the rail from a very low angle. This gives the impression that the rails are more natural and not toy like. Next use dark brown to spray the ties from directly overhead. This will eliminate the plastic appearance. Next use grimy black, and spray the ties between the rails to simulate oil and grease deposits left from the trains.

Painting backdrops is both fun and easy. Use a sky blue color and paint several layers starting at the top and making fewer passes on each layer. This will make the top look a deeper blue than the area near the ground where there tends to be more pollution.

You can add clouds by using white paint and a paper towel that has been torn with a jagged edge to use as a mask. Move the mask to allow for different patterns and you will have realistic looking clouds in just seconds.

Tools and other equipment

1) an airbrush

2) an air source - (a compressor is preferred)

3) paints in various colors for airbrushing

4) an appropriate thinner for the paint being used.

5) masking material such as photo frisket, masking tape, acetate, and card stock.

6) scissors, ruler, and a hobby knife.

7) cotton swabs, pipe cleaners, a stiff toothbrush, and a rag for cleaning the airbrush when you are finished.

Note: you can use plain lacquer thinner for cleaning the airbrush. This will be considerably more economical than the airbrush thinner.

© 2005 HR Trains & Toys, Inc - Don Morris