Now that this shape has been cut I'm beginning to sink it into a bowl form.  The particular shape I'm now hammering into is a cut out bottom section of an old gas cylinder.  It has just the right hollow underneath and is well rounded out to the edges, making this an ideal form for initial sinking when reversed and the hollow cylinder bottom is faced upward. Since I didn't anneal the sheet for this first rough forming operation, I'm using a heavier hammer.  The deoxidized 1/8" copper sheets I'm using comes in a half hard form so it's okay to start right in on the work after cutting out a shape.   I won't be able to take this form too far before I have to do the first annealing but it's malleable enough for general forming for the time being.