Sculptors and metal workers often wish to make metal look as if it has aged over time. To age metals quickly, you must speed up the natural process of degrading the surface through exposure to water and air. Additionally, to give hardened aluminum an aged appearance overnight, the finish must be darkened. Unlike other metals that can be darkened with a mixture of household chemicals, you must use a commercial chemical darkener to age hardened aluminum.
Dampen a cloth in a solvent to clean the aluminum. Be sure the solvent you choose doesn't leave behind any residue. Solvent examples include alcohol, acetone and lacquer thinner. Avoid solvents such as mineral spirits or kerosene that tend to leave a residue.
Abrade the surface if discoloration is present on the aluminum from oxidation. Use an abrasive brush or pad.
Apply a thin even coat of chemical darkener on the surface according to the instructions given by the manufacturer. Chemical treatments such as this can often be applied using a cloth or swab. Use a spray bottle to apply the chemical to large aluminum surfaces.
Monitor the chemical reaction that occurs on the aluminum surface. Apply a second coat of the darkener after it appears the reaction from the first coat has slowed. Continue reapplying coats of the chemical until a uniform aged finish appears on the aluminum.
Mix a gallon of water and two tablespoons of baking soda in a bucket. Dip a sponge in the mixture. Gently wash off the chemical with the sponge. Rinse the sponge in clean water as needed. This step helps neutralizes the chemical reaction on the aluminum.
Use a hair dryer to dry the surface of the aluminum. Use the warm setting on the dryer.
Use wax or lacquer to seal and preserve the aged finish.
Wear protective glasses and gloves when using the chemical darkener.