How to Form Copper Bowls From Sheet Metal by Hand
How to Make Metal Bowls Inexpensively
Forming metal bowls by hand can be a lot of hard work and takes skill to master. Thankfully, the tools you need are inexpensive and widely available. The bowls can be used as bobeches for candle holders or as decorative accents in metal art and sculptures. In the industry, this process is typically automated by a press that is capable of many tons of force. Sure, you get flawlessly smooth bowls, but it's obvious they are mass produced. The process can produce nearly perfect bowls, but a skilled artisan can produce high-quality bowls that possess much more character.
The Copper Bowl Forming Process
Forming copper bowls is a straightforward process. The quality of the finished piece is a direct reflection of the skill, effort, and tools used by the artisan. The process involves a few steps you'll need to consider to form the copper bowls and dishes.
- Cutting out disc blanks
- Annealing Copper
- Forming with a hammer
- Descaling the finished piece
1. Form the Disc Blank
One way you can form the blank is to take a round disc of sheet metal and use a hammer to make a depression. Work from the outside edges in while rotating the disc. This method is mainly used for softer metals such as copper and brass.
When you do this, draw a circle pattern on a piece of paper. Cut it out and trace it on the sheet metal. The flat metal disc is cut out and, if it is made of copper or brass, is annealed by flame heating so the metal becomes softer and more malleable. This is important because these metals will harden during the hammering process. They may need annealing a few times during the process.
2. Anneal the Copper
The copper needs to be softened in order to form it into bowls or any other shape. This process makes shaping the metal possible with hand tools and is called annealing.
Annealing involves heating the copper to a dull red heat and allowing it to cool. This makes it very soft and pliable. When it's hammered or stressed, the copper slowly begins to harden. If an elaborate copper project is underway, it will need to be annealed a number of times. Hammering a copper sheet that is hardened can lead to disaster because it becomes more brittle, tears, or cracks under stress. It's better to be safe than sorry.
How to Raise a Copper Vessel
3. Form the Sheet Over a Hole or Depression
Another method which is easier to do for harder metals like steel alloys is to form the sheet metal over something to shape it. This can be a cylindrical hollow object like steel pipe with thick walls or a heavy plate with a circular hole cut into it. Make sure the metal piece is larger than the intended bowl size. This is called 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 hole. This helps it take a bowl shape. A little diligence is needed here, as too 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. You can see an example in the photo below.
4. Planish and Smooth the Copper Bowls
Now, you've cut out a copper disk and created a rough bowl form. If you used a metal hammer like a ball peen hammer, the bowl would be quite bumpy and rough. To smooth it out, you will have to planish the copper bowl on a smooth-forming tool.
You can use specialized metal-forming stakes that cost a couple hundred bucks. If that's not in your budget, you can utilize any hard, smooth, and steel-domed surface.
- Top of an oxygen gas cylinder
- Dolly for automotive bodywork
- Spherical ornamental finials.
Planishing copper takes more technique than excessive force. Position your copper over the domed work surface and strike with a hammer on the same spot. Do this as you move the copper piece, always striking the domed steel surface at the same spot.
- Planishing hammers are very useful for finishing copper bowls. After the initial forming with a ball peen hammer, the planishing hammer can be used with a stake or auto panel dolly to smooth out the bumps of the bowl.
You can see the video below for additional tips.
Simple Steps to Planishing Copper
5. Descale the Formed Copper Bowls
After hammering and a few annealing cycles, your copper bowls will be covered in heat scale. This scale consists of varying amounts of copper(II) oxide and copper(I) oxide. The copper(II) oxide is black and easy to dissolve in acids. The more tenacious copper(I) oxide is pink, rose, or red. You can use a few solutions to pickle the copper and make it easier to buff.
1. The fastest and most economical way is to use diluted muriatic acid. This will remove the black and brown scale, but it will also leave the metal dull and pink. To make the solution more effective, add an oxidant like hydrogen peroxide to oxidize the scale into a soluble form. This will make burnishing it to bare metal much easier. The liquid will turn green in the oxidation process because of the formation of copper(II) chloride.
- It would be advantageous to save this green liquid for future use because it can be used many times over. When the solution gets too dark, just add more peroxide. If it loses its bite, add more muriatic acid. When the solution becomes too filthy, simply drop in an iron nail and the copper will drop out as a granular substance. Decant the iron solution into a separate container and neutralize it with baking soda. After this, it can be safely flushed down the toilet. The copper granules can be mixed with borax, fused with a torch, and scrapped.
2. Another solution is sodium bisulfate. This is pH down used for spas and swimming pools. It is supplied in round globules and referred as "dry acid," as it is a safer alternative to sulfuric acid. This chemical produces sulfuric acid and cleans the copper of its scale. After the solution is spent, you can use it as a copper-plating solution.
Types of Hammers for Copper Forming
Although it's possible to form bowls and dimensional copper vessels with a simple ball peen hammer, it is by no means is the only way.
- One option is plastic mallets. Copper is a soft metal, especially when it's annealed. Because of this, it is exceedingly difficult to get a smooth copper surface due to the marring effects of hardened steel hammers.
- A ball peen hammer can be used to shape copper bowls. The ball end, with its smooth finish, is like a forming stake. The ball peen hammer head can even be put in a vise and the bowl placed over the end. Then, you can gently strike it with a finishing hammer.
Copper Bowls as Decorative Accents
Normally, when one pictures a smith hammering a copper bowl, their thought drifts to traditional bowl shapes that are stand-alone pieces. Although the decorative round copper bowl on a table is always a pleasing sight, copper bowls can be formed and exhibited in unique ways.
One novel approach is to display a bowl as a work of art. How would you use a copper bowl?