Step 4: Pickle the Metal
This step is critical so don't skip it unless you actually want non-uniform rusting. At first I didn't do this and several areas would not rust because the solution could not penetrate the surface of the metal. You can see this in the picture below. I simply hung up the degreased bell and sprayed it with solution. You can see where the solution did not penetrate. Those areas did not rust at all. I then pickled the entire bell and after I did it rusted all over.
Believe it or not, you can pickle metal with the same ingredient that is used to pickle cucumbers. Yup, you guessed it, vinegar. Place your object where you can spray it from all sides, away from anything you don't want to get sprayed, including people, pets, and other objects. Put on your safety goggles and gloves. Put some vinegar in the spray bottle. Not too much, just enough to cover the object several times. Spray the object from top to bottom all around. Soak it good. Let dry and repeat several times. The more the better. Placing the object in direct sunlight will speed drying. The acid in the vinegar will etch the surface of the metal so chemicals can penetrate. If you skip this step and proceed with the next step or don't like the results of the next step, just come back to this step and spray again with vinegar. The acid in the vinegar will dissolve most of the rust. Don't worry about it. This is normal.
That's it. Now we're ready for the fun part.