Initial steps to getting ready to antique brass
Before you can antique the brass piece, the type and composition of the piece you are trying to antique makes a huge difference on the final result of the patina achieved.
First determine that it is solid brass. Some pieces maybe iron, steel or zinc with brass plating. Solid brass will not attract a magnet. It a magnet sticks to the piece, it may be just brass plated. The piece may still be antiqued. You must be careful with the surface preparation. You must be careful using strong abrasives as you may completely remove the plating. Plated brass will not antique predictably. Strong chemical used in the oxidizing process may eat completely through the plating, exposing the underlying metal.
The thickness of the brass can also affect how even the final patina is or how much variation is seen throughout the piece. Sheet metal that is rolled will have an even thickness and composition. The final color achieved will be even and predictable throughout the piece.
Solid brass that is cast or sculpted will have variation in the thickness and the composition of the material. There are variations in how different parts of the piece will cool during the casting process. There will be variation in how the different parts of the piece will respond to the antiquing process.
Most brass comes with a protective finish of lacquer or varnish. This must be removed from the surface of the raw brass to allow the antiquing process to affect the brass surface. In addition, the surface can have impurities and contaminants that can also prevent the brass from coming in contact with the antiquing chemicals. This includes dirt and oils from handling the piece. These contaminants must also be removed to have a clean surface prior to proceeding with the antiquing process.
If you are starting with a new piece, you may purchase brass that does not have a protective film to save you this step. It may still need to be prepared to removed surface contaminants.
How thorough the surface is prepared with effect how well the antiquing process takes and the appearance of the final result. There are two general methods to surface preparation.