Cast Aluminum / Zincated / Flash Copper / 3 hours of acid copper / with an aux. anode made of 1/2" copper pipe. Finally enough to sand down through all the pits. Sanded with a pneumatic orbital, 320 grit. Finished buffing with my brand new 3/4 HP buffer from Caswell that I only have great things to say about - black on spiral/white on loose. Just about ready for nickel. This is probably about the biggest piece on can do in a 4.5 gallon kit comfortably without double dipping.