Dampen a sponge in warm water. Shake a can of powdered kitchen cleanser over the sponge until you cover it evenly. Wipe down the faucet with the sponge and cleaner, removing caked on grease. Rinse it well and pat it dry with a paper towel.
Put on latex gloves. Buff the copper with a hand pad of 360 to 400 grit. Follow with an ultra fine hand pad of 800 to 1000 grit.
Dampen a rag with denatured alcohol and wipe down the faucet. Pour 1 cup rapid fixer into an empty 2-liter bottle. Add 2 cups of water. Replace the cap and shake the contents well.
Place 2 to 3 inches of the diluted fixer onto a glass tray. Place the copper faucet into the liquid. Gently shake the pan so the liquid keeps covering the copper well.
Watch as the copper faucet begins to darken over a few minutes. Don't let the color get too dark because it won't resemble copper anymore. Allow the copper to air dry. Once dry, spray a clear acrylic coating on it evenly. Allow the coating to dry overnight.