To learn metal shaping, it is best to start with a few basic tools such as a shot bag, a wooden bossing mallet and a large tree stump with a dish shape carved in the middle approximately 6" in diameter and 3" deep hollowed into the center. The log should be about 24" in diameter and height, (you can place the log on a pedestal to your desired working height). The hammer and shot bag can be purchased from a company such as U.S. Industrial Tool and Supply Co. or Eastwood. It is best to begin with hammers and shot bag because the beginner can better control the basic hand tools. You are now ready to start.
Select a piece of aluminum or steel about 15" in diameter. Using the blunt end of the wooden bossing mallet and the hollowed shape in the top of the log you can begin shaping your panel. The tree stump is used to quickly bring shape into a panel so don't be shy about hitting it. Hammer a shape 3" in depth and 12" in diameter into the center of the circle. Now proceed to the shot bag and slowly work out any gross imperfections. When this is accomplished, return to your tree stump and using the flat part of the log surface, you can begin to shrink the outer 1-1/2" of the dish. The shrinking process is best described as a gathering procedure. You will notice that the outer portion is wrinkled while the center section has a somewhat "drawn" appearance. The inner section of the panel is stretched from the hammering while the unworked outer portion is showing a series of undulating "V's". What you will be trying to do is increase the thickness of the metal by forcing the little V's in against themselves. Lay the edge of the panel on the flat portion of the log so that the wrinkled portion loosely resembles an inverted vee. Take your rawhide or wooden mallet and strike the top of the vee with a quick blow. This will cause the metal to increase in thickness thereby shrinking the edge of the panel. With a little bit of practice you quickly learn how to stretch and shrink metal. Just remember to go slowly and try to think about what is happening to the metal with each blow of the hammer.
It is best to begin with these techniques because the novice can gain a real sense of accomplishment with a relatively small amount of expended energy. Remember to try to think of the metal as modeling clay because the two mediums react exactly the same way to applied mechanical energy.