Steel is useful for a plate you may wish to reuse many times. Thick brass and bronze will produce plates that can be reused. Read about etching in a printmaking book for more details before you proceed. Use in well ventilated area and wear rubber gloves and eye protection. Do not inhale fumes.
Ferric chloride is a salt which gives a clean etch to copper-based alloys.
Follow directions on the bottle. Wear rubber or latex gloves. Tapes such as electrical tape or brown packing tape can be used as resists. Agitate occasionally for better action. Check the depth of the bite frequently.