To define the annealing process in simple terms means to remove any stresses and return material to a soft and workable state ie.
Annealing copper sheet metal.
This malleability allows you to hammer and mold the copper into any shape you wish without cracking the metal.
Copper silver and brass can be either cooled slowly in air or quickly by quenching in water.
Annealing is a method of softening metal that has been hardened by one method or another.
Darlene armstrong director and co owner of the denver school of metal arts shows you how to anneal a sheet of copper using an acetylene torch.
Annealing copper makes it softer and less brittle which allows you to bend it without breaking it.
Copper is one of the metals that hardens when it is worked bent stretched.
Making it more malleable.
In the case of ferrous metals such as steel annealing is performed by heating the material generally until glowing for a while and then slowly letting it cool to room temperature in still air.
You can anneal any grade and thickness of copper as long as you have a flame that can transmit enough heat to the metal.
If all you want to do is color the copper a small torch will likely do the job but you are not likely to be able to actualy anneal any signifiacnt size piece.
This is especially so in metals that become work hardened like copper and brass although brass can become very brittle and fracture easily especially if it has been heated.