Similar to lost wax carving, casting organic material is very exciting in that the outcome is quite unpredictable. Instead of starting with a wax, you can use an actual organic object that has been dried out (moisture will expand and explode in the kiln during the burn out process). By connecting the organic object to the base of the steel flask and pouring the high temperature investment plaster around it, you can create a pathway for molten metal to follow, providing the material inside burns out completely in the kiln. Often, this burnout takes longer than wax - bone for instance needs upwards of 16 hours to turn to dust. There is also the issue of carbon, which sometimes remains in the investment and shows up on the metal surface. However, it is an awesome experiment, and if you hold loose your expectations of outcome the results can be astounding! Orchids are my favorite: I had a wonderful casting class a few years ago that pushed me to perfect the process. I believe almost everyone in that class walked away with a silver or gold orchid.