Realistic cracks can be added with an airbrush.
An airbrush is a tool used by many artists to spray a controlled stream of paint and air onto a canvas. Airbrushes are used to create a variety of effects. One such effect is painting cracks that can look very realistic. To do this, you will use the least amount of air pressure possible to produce fine lines. Cracks can follow any pattern or direction, making them a very free-form detail.
Instructions
1. Connect a double-action airbrush to an air compressor with an air hose.
2. Fill the airbrush's paint reservoir with black paint.
3. Turn the air compressor's pressure down to 10 PSI.
4. Hold the airbrush near a piece of scrap paper and press the trigger to begin the air flow, then pull it back to begin the paint flow. Draw a line with the airbrush.
5. Increase the pressure by 5 PSI at a time until the airbrush produces a thin, controlled line. The PSI required will vary depending on your airbrush and paint.
6. Aim the airbrush at the surface that you want to paint cracks on. You will begin at the base of the crack, which is often at the edge of the surface.
7. Airbrush an irregular line onto the surface. Taper the end of the line to a point by moving the trigger forward, which cuts off the paint without affecting the air.
8. Add additional lines and cracks coming off of the main line. Look to pictures of lightning bolts for inspiration if needed.
