It will just burn out in the kiln or if you decide to poke holes in the sphere as part of the design you may be able to gently remove it through a hole in the clay.
How to make a ceramic sphere.
Once the ball shape is formed use the pin tool to pierce the clay and pop the balloon inside.
Ceramic mold making techniques.
It s ok to leave the balloon inside.
If one has not been left in the forming process an opening big enough to insert a hand is carved out at this point.
4 minute video about making a sphere from terracotta clay.
Remember you must pierce a hole in the sphere to allow air to escape.
If your sphere is larger than 2 or 2 5 inches in diameter you will need to hollow out the insides with a small scoop.
If the clay is only 2 or 2 5 inches in diameter insert a needle tool into the sphere and insert it at least half way into the sphere so that the sphere is broken up in the center and no part of the sphere is more than 1 5 inches.
Thirty five year art education veteran gary benna s 7 minute video uses synchronized views.