HOW ARE THEY MADE? The sphere is turned on a lathe then conical holes are drilled towards the center. The maker has a set of "L" shaped tools the one with the longest upright has the shortest cutter and the one with the shortest upright has the longest cutter. Starting with the longest tool he lowers it to the narrow bottom of each hole in turn and rotates it to cut the innermost ball free. Then he gets the second tool which does not reach so far down the hole but can cut a wider arc and separates the second ball. He continues working from the innermost to outermost shell. For obvious reasons, usually only the outermost balls are elaborately carved.
The outer layer is twice as thick as the inner layers. This is because the two outer layers are fused together. The reason for this is that the outer layer with the dueling dragons is carved so deeply that if it were free moving it would be too fragile and shatter, so it has to be fused to the 2nd layer to make it strong enough to avoid breaking. The very inner ball at the center is also counted as a layer making up the total number of layers. Therefore counting the center ball and the other moveable layers will make up the total layers of the ball minus two layers, those remaining two layers are the ones fused together making up the outer shell.
For example - an 18 layer ball will have 16 moveable layers (including the center ball) plus the 2 fused outer layers.
