Rust that had eaten away at the metal portions of the sign (Figure 4.14) was created using a modified brush tip. The basic tip is exactly the same as the one I used to create the damages on the stone wall in the painting "Oakland" and the stone wall in this painting (Figure 4.15). In fact, in many situations I often use this particular brush shape.
Figure 4.14 The rust areas of the metal of the sign.
Figure 4.15 The brush tips have been modified to randomize the stroke.
Because the damages on the stone surfaces were visible due to the affect of lights and shadows within the damaged areas, the Fill Opacity for the layer containing the strokes was lowered to zero, so the effect was created using the layer style.
For the rust on the signs, the Fill Opacity was left at 100% because the stroke needed to be visible. Color made the difference here. One function of the Brushes panel that was not used in the other instances was utilized here—Color Dynamics. In the Color Dynamics section the Foreground/Background Jitter was set to 100% (Figure 4.16). This feature randomly applies the colors assigned to the Foreground and Background to the brush tips as they paint over the canvas. Altering the Saturation and Brightness Jitters introduced further randomness to the colors being applied. Adjusting the Hue slider just a bit added even more randomness. Pushing the Hue slider too far produces unwanted colors, so I kept it low.
Figure 4.16 The Color Dynamics section of the Brushes panel.
Setting the Foreground color to a brown and the Background to an orange (Figure 4.17) created the effect of rust when I stroked the canvas with the altered brush tip.
Figure 4.17 The Foreground and Background colors were set to simulate the colors of rust.