Hi, Im trying to make an art project and would like to burnish small squares of copper sheeting using a blowtorch, same with beaten pieces. Can you tell me if you can do them this size without them warping etc?
Answer: In most cases any metal will warp when you hammer it or heat it to much. When I hammer copper sheets that are 36" x 120" in size I have to fasten it down otherewise it will warp into a complete tube. After I finish hammering it I run it through a slip roller to flatten it back out making it much easier to work with on smaller pieces you could actually use a rubber mallet or a dead blow mallet to take some of the warping out. There are places that sale hammered and burnished pieces. If you are only trying to darken the copper in a burnished manner you could look at your local craft store and see if they carry "Liver of Sulfer" or Google it there are plenty of options for it.