How to antique brass with ammonia:
Ammonia vapor oxidizes brass to a green brown patina. This is very close in appearance to a natural, aged patina. Ammonia can be obtained from hardware stores. Ammonia fumes can be irritating. Use only in a well ventilated area.
brass to be antiqued
plastic container with tight lid, large enough to hold the brass
wax or lacquer
Put on the gloves. Prepare the brass piece for antiquing by cleaning the surface of lacquer, dirt and oils. Create a wooden shelf in the bottom of the plastic container. Fill the plastic container with ammonia such that the level is below the top of the wooden block. Place the brass piece on top of the wooden platform with care such that the brass does not come into direct contact with the liquid ammonia. Place the lid tightly on the contained.
Smaller pieces may be suspended in a glass bottle filled with ammonia. Tie a cord to the piece and suspend from the bottle opening. Screw on the lid to create an air tight space and to hold the piece above the ammonia liquid level.
Allow the ammonia fumes to antique the brass. This will take a few hours. Monitor the color change progress and once your are satisfied, remove the brass from the container. The longer you leave the piece in, the color will become darker brown. Leave the piece in a well ventilated area to remove any ammonia residue.
The ammonia bath can be reused for other pieces. Eventually it will lose its potency as the ammonia vapor easily evaporates and needs to be replenished.
Protect the antique brass patina with a coating of wax or clear lacquer.