Sink a small bowl or spoon - metalworking.straw.sink PEP BB

I've been meaning to do this BB for some time now since what I do for a living is craft metal bowls/vessels.  However, the technique I am almost always using is raising rather than sinking.  (Of course I have already done the raising BB!)  Sinking is different in several ways one of which is that the process stretches the metal out, making it thinner.  

On this particular project I'm working on this is what I needed to start out. There's a quirk of metal suppliers here in the US, where I am, such that I can easily get sheets of silver that are 6 inches wide.  However, if I want anything wider I need to jump up to 12 inches in width for which I pay a premium per ounce price.  If I want wider than 12 inches I'm out of luck and will need to manufacture the sheet myself.

Anyway, for this piece I essentially want an 8 inch disk of 18 gauge fine silver.  The most cost effective way for me to do this is to purchase a 6 x 6 inch sheet of silver that is thicker and has the same basic weight of metal in it as that 8 inch disk would have.  I calculated this to be 12 gauge.  So that is my starting material, a 6 x 6 inch square of 12 gauge fine silver sheet.  From here I scribed out my disk and cut the corners off, filing the edges to remove any sharp burs.  

My sheet came in a softened state so I didn't need to anneal initially though I did between each subsequent course of sinking.  I took it to my sinking stump and did the initial round of sinking utilizing a specialty metalsmithing hammer designed just for this sort of work.  I actually don't much like using that hammer as the head is just too long.  The length is very handy to have when the bowl starts developing depth, but it is very hard on the wrists to control.  I actually ended up using my normal raising hammer for most of the work, switching to the deep sinking hammer when I got to the deepest middle sections of the bowl.

My goal with the sinking work was not to actually end up with a finished piece.  Instead I was just looking to get the vessel form started and thin the 12 gauge sheet down to something more around 18 gauge.  With sinking the starting circumference doesn't change much, unlike raising which will compress the metal and reduce the circumference.  So to tell when I was where I wanted to be I was checking the measurements of overall height/depth plus the width, wanting them to equal around 8 inch total.  In the end I went for a bit more, ending up around 6.25" x 2.5", because it wasn't visually looking like what I'm used to seeing when working with 8 inch diameter pieces to start with.  At this point I have finished the later raising courses for this piece getting to measurements of about 4 inches high by 4 inches wide, just what I was aiming for.  Now I'm going to spend the real time chasing in detailed designs.  I may post a photo of the finished piece later once it's done.

For this BB though here are my documentation images for the sinking work.  Personally I feel like it should only be approved for 2 points of the potential 6, if it's even deemed worthy of approval.  It is a very basic job of sinking a bowl with hardly any refinement, and not even that much depth compared to what is possible with this technique.