When fashioning brass into vases, furniture hardware, sculptures, jewelry and decorative objects, artists choose to darken the brass either before or after it is transformed from a simple piece of metal into assorted shapes. Several methods are available to accomplish this darkening.
Commercial Solutions
Brass darkening solutions are available at restoration and antiquing websites and stores. The liquids are available in various sizes to accommodate small to large projects. You simply submerge the brass into the liquid, which darkens the brass to different levels depending on how long it is left in the solution, and then rinse it clean with cold tap water.
Fuming
Another way to darken brass is through exposure to ammonia fumes. Suspend the metal above a bowl or pot of ammonia, watch it darken and remove it when the desired level of darkening is achieved. To hasten the process, place the ammonia and metal in a covered jar or place it in a glass bowl covered with aluminum foil, which intensifies the fumes. This method is slower than the commercial solution but provides a higher level of control.
Flaming
If you have a well-ventilated area that is safe for fires, hold the brass above flames to darken it. This method tends to darken larger areas of the metal, but the effect can be altered by buffing out overly darkened areas with fine steel wool subsequent to flaming.
Homemade Chemical Solutions
Ferric nitrate, available at chemical suppliers and jewelry supply stores, can be used to make your own brass darkening solution. Mix 1/2 tsp. ferric nitrite with 2 cups distilled water and stir until dissolved. Gently heat the brass to be darkened in an oven set to low heat and while it’s still warm, apply the liquid to it with a brush or spray bottle. Let it dry and reapply for more darkening until the brass is the desired color. A more complex process requires adding ferric chloride to the ferric nitrite mixture, which results in a deeper, more complex darkening on the brass. Apply the solution with a brush or spray attachment and when the first hint of darkening appears, rinse the brass under cool running water and dry it with barely damp newspaper. Buff the brass with fine steel wool and let it cure for a minimum of 12 hours to let the colors develop. Repeat the procedure until the preferred color is achieved.