Place the headboard on an old sheet, which protects your floor. Protect your hands and face with rubber gloves and a mask. Apply a coat of lacquer thinner to the metal with a paintbrush. After 60 seconds, wipe off the metal with an old rag. The lacquer thinner removes any varnish or clear coating.
Clean the headboard with rubbing alcohol. The liquid clears away any dirt or debris left on the metal. Fill a spray bottle with water and lightly mist the piece. If the water beads on the metal, apply more lacquer thinner. When no beads appear, the piece is completely clean.
Turn the handheld blowtorch on low and aim the torch at the metal. As soon as the metal turns orange, move the blowtorch to a different area of the metal. Keep moving the torch over the headboard until every area heats to an orange shade.
Empty the spray bottle and replace the water with distilled white vinegar. Spray the vinegar on the headboard and let the piece sit outside in the sun. The acid in the vinegar changes the color of the metal and slowly creates a dark patina.
Check the headboard once a day and apply more vinegar as necessary. Keep spraying more vinegar on the piece until it reaches the dark patina you want. If the piece has an unusual shape, apply the vinegar to the metal with a paintbrush.