aluminium and copper claw demonstration fold forming
Here is a quick outline on how to create a curved form by beating on the folded side of your piece. I've shown both aluminium and copper so you can see the different approach needed as you work.
Start by drawing your idea on paper and cut it out. As you work, think how it will translate to a template. Here I drew the outline of four talons on the aluminum sheet with a regular marker.
After cutting out the template from the metal, I gently bent the talons into a curved shape in preparation for folding each into a sharp point. It's best to do this stage slowly and carefully because once you fold, it's difficult to undo. You'll see with this aluminium piece I had to trim later. The copper will be harder to bend, to cut and to shape, but you will have a stronger object in the end and you will be able to push the shape further.
Next I took a slightly rounded hammer and gently beat the folded edges of the claws, making sure not to hit the outer edges. This ensures that the metal that I displaced with the hammer was pushed outwards and down the spine of the fold, and created the curve I wanted to form along the folded edge. Even in this first round of hammering, you can see the metal move away from the straight edge. Two passes with the hammer, either one on each side, or twice down the same side if the hammer blows are wide apart, is enough. (Be careful not to hit aluminium metal too hard or the metal will split.) When you feel the metal is no longer soft, maleable, has lost its annealed quality, its time to heat it up again. Remember, the aluminium you will be using is so light and thin you should be tapping it rather than hitting it hard.
Already cut, folded, and hammered down the spine twice, (notice the nice curve developing) this single talon is being annealed for the second time. Notice the aim of the flame, not touching the metal with the inner blue and hottest part, and the reddish glow of the metal as it reaches the right temperature.
This video shows the hammering process. On copper you can afford to work the metal a bit harder than aluminium.
Don't forget - aluminium users - that you only need the slightest brush with a flame to get the warming up that you need to anneal the piece. Keep the torch far from the piece and watch for the tiny bubbles that can form on the surface just before the surface starts to melt. You can see a little of that on the back of the bird foot over here.
After heating ever so gently with a torch, I slip the piece, with tweezers to avoid getting burnt, into a water bath to be sure its cool for the next found of hammering. Drying the metal before hammering ensures you wont get your steel block damaged (see the bottom corner of mine which needs the rust sanding off).
When you think you are almost done, ie the metal has taken the form that you want, it's time to heat it one last time. When its cooled, open the fold very carefully, watching that your fingers don't get sliced on the sharp edges. I show you here how to open with a wooden object, how to file, and how to burnish your work.
