PAint Rust effects

Rust Effects

Andy (Anmatr) Nelson won our forum's August 2004 competition with his superb Battletech tower. Here he reveals how he created the rust and weathering effects.
To represent painted steel, with the paint chipping off and exposing bare metal, start with a base-coat of whatever color the metal was painted when new. I use ordinary craft acrylics (Apple Barrel, Ceramcoat, Americana).
Next, use the bristles of a brush in a stabbing motion to apply many tiny dots of steel color. The steel color can be either a pure silver color, or a mixture of silver and rust color (a reddish-brown like raw sienna or burnt sienna). When the paint dries slightly and gets tacky, dab a sponge to distribute it around a bit more. The sponge will pick up larger dots that haven't dried fully and deposit them elsewhere.
Repeat this procedure with a rust color to represent old rust on top of the exposed bare metal. Then apply a wash of dark brown or reddish brown to represent overall grime and rust. The result will be a mottled steel look.
Sometimes I'll go back with a brush and touch-up the edges with some rust, silver, or silver-rust, depending on whether the steel has been walked over lately. Steel in use as ramps, doors, or flooring will have new steel constantly exposed. Steel that is less accessable (like the armour on the tower) will have most exposed areas covered with rust.
A variant of the method is to paint the whole area steel color and then apply sponge or brush dabs of rust. Then apply a wash. This is for a different look of bare steel that is beginning corrosion.

The armour plates on the tower were supposed to look like painted steel that had weathered and begun to rust. They were painted a light grey and then dabbed with rust. The rust would tend to concentrate on the edges and corrode inward under the paint. Therefore I concentrated the sponging around the edges. The plates laying on the floor around the base of the tower are a good example. Rust will also concentrate where the paint has been knocked off e.g. around bullet holes.
After the plates on the tower had been rusted as described above, I added streaks where rain would have washed rust particles down from heavily rusted areas. These streaks can be done with drybrushing, washes, or quick, downward strokes with a watered-down rust color. These streaks are more intense from their source and fade and fan out slightly as they travel down.
Bird droppings are applied the same way, but they start from the top edge or anywhere birds might perch.
The armour plates were glued to the tower before the streaks were added, since I didn't know what direction was going to be "down" until each plate was glued on.
Another weathering technique is to paint over some of the rust to represent maintenance. The freshly painted areas should be weathered a little bit as well, depending on how recent the repainting should appear to be.
Details of the tower's construction can be seen by clicking here.