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Forming copper bowls from sheet metal by hand
Metal Bowls the Inexpensive Way
Forming metal bowls by hand can be a lot of hard work and takes skill to master. Thankfully, the tools need are inexpensive and widely available. These can be used as bobeches for candle holders or as decorative accents in metal art and sculptures. Usually in industry, this process is automated by a press that is capable of many tons of force. Sure you get flawless smooth bowls but it is obvious they are mass produced. The two processes mentioned will produce nearly perfect bowls in the hands of a skilled artisian but they will have more character than the manufactured ones.
Process for Forming Copper Bowls
Forming Copper Bowls is a straightforward process. The quality of finished piece is a direct reflection of the skill, effort and tools used by the artisan. There are a few steps to consider while forming copper bowls and dishes.
- Cutting out disc blanks
- Annealing Copper
- Forming with hammer
- Descaling Finished piece
Copper Bowls From Disc Blanks
Forming from disc blank
One method is to take a round disc of sheet metal and, using a hammer, forming from the outside edges to make a depression while rotating the disc. This is mainly used for softer metals such as copper and brass.
The way its done is a circle pattern is drawn on paper and cut out and traced on sheet metal. The flat metal disc is cut out and ,if it is copper or brass, it is annealed by flame heating it so the metal is softer and more workable. This is important as these metal will work harden during hammering. They may need annealing a few times during the process.
Copper Sheets on Amazon!
When forming copper into bowls or any shape for that matter, the metal needs to be softened. This makes shaping the metal possible with hand tools. The process used to make copper and its alloys workable is called annealing.
Annealing is essentially heating the copper to a dull red heat and allowing to cool. It becomes very soft and pliable. When hammered or stressed, the copper will slowly begin to work harden. So if an elaborate copper project is under way, it will have to be annealed a number of times. Hammering copper sheet that is work hardened can lead to disaster. As the copper hardens, it becomes more brittle and tear or crack under the stress. So better safe than sorry.
Raising a copper vessel
Forming sheet over hole or depression
Another method which is easier for the harder metals like steel alloys is where a piece of sheet metal larger than the intended bowl is placed over a cylindrical hollow object like steel pipe with thick walls or heavy plate with a circular hole cut into it. This method is referred to as sinking.
Essentially, the sheet metal is placed over the hollow object and the round part of a ball peen hammer is used to force the metal into the whole taking a bowl shape. A little diligence is needed here as to much hammering can cause the metal to crack and split. An example of an improvised tool or mandrel is the schedule 40 steel pipe with a square bar welded on to secure in a bench vise featured in the photo.
Planishing and Smoothing Copper Bowls
You have cut out a copper disk, and you created a bowl in rough form. If you used a metal hammer like a ball peen hammer the bowl will be quite bumpy and rough. To smooth it out, you will have to planish the copper bowl on a smooth forming tool. There are specialized metal forming stakes that cost a couple hundred bucks. If that is not in your budget there are alternatives. Any hard steel domed smooth surface will suffice. You can use the top from an oxygen gas cylinder, a dolly for automotive body work or spherical ornamental finials. Please consider the video posted below.
To planish copper does not take excessive force. It is more technique than anything. You position your copper over the domed work surface and strike with a hammer on the same spot. Doing this, you move the copper piece always striking the domed steel surface at the same spot.
Simple Steps to Planishing Copper
Descaling Formed Copper Bowls
After hammering and a couple of annealing cycles, your copper bowls will be covered in heat scale. This scale consist of varying amounts of copper(II)oxide and copper(I)oxide. The copper(II)oxide is black and easier to dissolve in acids while the copper(I)oxide is pink, rose, or red and a little more tenacious. There are a few solutions to use to pickle the copper so it can easily be buffed. The fastest and most economical way is to use diluted muriatic acid. This will remove the black and brown scale but leave the metal dull and pink. To make this solution more effective, add an oxidant like hydrogen peroxide. This will oxidize all the scale into a soluble form. This makes burnishing to bare metal much easier. The liquid will turn green in the oxidation process due to the formation of copper(II)chloride. It would be advantageous to save this green liquid for future use. It can be used many,many times over. When the solution gets too dark, just add more peroxide. If it loses its bite, add more muratic acid. When the solution becomes to filthy, simply drop in an iron nail and the copper drops out as a granular substance. Decant the iron solution into a separate container, neutralize with baking soda, it can then be safely flushed down the toilet. The copper granules can be mixed with borax and fuse with a torch and scrap the copper.
Another solution is sodium bisulfate. This is pH down used for spas and swimming pools. It is supplied in round globules. It is usually referred as "dry acid" as it is a safer alternative to sulfuric acid. This chemical produces sulfuric acid in solution and the copper is cleaned of its scale. After this solution is spent, it can be used as a copper plating solution.
Types of Hammers for Copper Forming
Although it possible to form bowls and dimensional copper vessel with a simple ball peen hammer, by no means is the only way. One option is plastic mallets. Copper is a soft metal, especially when anneals. Because of this, it is exceedingly difficult to get a smooth copper surface due to the marring effects of hardened steel hammers.
Ball Peen Hammer
Aside from forging hot metal bars and setting solid rivets, a ball peen hammer can be used to shape copper bowls. The ball end is like a forming stake with its smooth finish. The ball peen hammer head can even be put in a vise and the bowl placed over the ball end while gently striking with a finishing hammer.
Midecentury Nail Art with Copper Accent Bowl
Copper Bowls as Decorative Accents
Normally, when one pictures a smith hand hammering a copper bowl, their thoughts allude to tradional bowl shapes that are stand alone pieces. Although the decorative round copper bowl on a table is always a pleasing sight, there are numerous ways to form and exhibit hand formed copper bowls.
A novel approach is to incorporate a hand formed copper bowl, as an accent piece, into a work of art. Consider this modern midcentury braze welded nail sculpture with a 5 inch copper bowl. This bowl was hammered into a semi rough finish then brazed onto the geometric nail framework that mounts to the wall.