Smoothing surface of bowl with the planishing hammer
If you went on hammering too long after your bowl is shaped, the bowl would crack or perhaps break, for hammering leaves copper hard and springy. So you must soften it before you can safely hammer any more. To do this I hold the bowl over a gas range until it is red all over, then I plunge it into cold water. This heating to soften up the copper is called annealing. Repeat the hammering until the bowl takes on the shape of the design.
In this way one can get the shape desired
Now take your round top stake and put it into the vise. Place the bowl over the round top stake, and with the planishing hammer, beat the surface until it is perfectly smooth, driving the metal just hard enough to flatten the bumps made by the hammering in the wooden block. If carefully done the surface will be true and bright and covered over with brilliant facets. A skillful hammer-man can really drive the metal in any direction he may wish. In this way you make a bowl out of one piece of copper. The top of the bowl will be ragged. Cut this rough edge with a pair of shears. File the top with a smooth file until it is perfectly true. A good test to make sure of this is to lay the bowl down on a plate of glass, or hold it up against the window pane. If there are still any tiny openings left in the edge the light will be easily seen through them. More filing must be done until no light comes through from the smallest space. This done, take a piece of emery cloth and rub the edge of the bowl until the file marks disappear. If you lap the cloth over the edge your rubbing will leave a rounded edge, which is just the finish it should have.
Marking the edge of the bowl