You can anneal any grade and thickness of copper as long as you have a flame that can transmit enough heat to the metal.
Annealing copper sheet metal.
This malleability allows you to hammer and mold the copper into any shape you wish without cracking the metal.
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.
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.
Making it more malleable.
How to anneal and firescale copper sheet metal.
Annealing is a method of softening metal that has been hardened by one method or another.
This video shows you how to safely use the torches in this classroom as well as anneal a piece of copper and add firescale.
Annealing copper makes it softer and less brittle which allows you to bend it without breaking it.
Annealing is a technique that all metalsmiths will.
Copper silver and brass can be either cooled slowly in air or quickly by quenching in water.
Copper is one of the metals that hardens when it is worked bent stretched.