When I first started trying to make a wooden geodesic sphere ten years ago, I ended up making a lot of expensive firewood. So I then started using cheaper plywood until I got all of the angles figured out. When I sanded the first successful  plywood sphere the pattern that emerged was a nice surprise. I now make them out of a much higher grade of plywood, but the effect is the same.
 
This sphere is made of standard Baltic birch plywood.  Normally it is used for cabinet drawer sides because of its stability and strength. It has 13 layers of birch veneer in its 3/4" thickness. Birch wood varies in color from creamy beige to darker brown tones. The inner plies will have a variety of streaks ,small knots, and splits, which all add to the character of the finished piece. The reddish brown ring around each layer is actually the adhesive used during the plywood manufacturing. All Baltic spheres will have a similar pattern, but I never know what colors and character are on the inside just waiting to come to the surface.
 
I have been asked many times which of my designs is my favorite. The answer is Baltic. I love the fact that this is not made with some rare exotic wood. It is a made with a strong, reliable material that was never meant to be beautiful. Baltic just needed someone to give it a chance to shine.