The Chia pets have grooves to hold the seeds. The grooves are scratched into the terra cotta before it is fired, so they are not uniform and have a lot of rough/porous surface area that allow the roots of the germinating seedlings to firmly attach.

The terra cotta (since it is not glazed) allows the water on the inside of the Chia Pet(TM) to keep the porous terra cotta uniformly moist. This provides the water for them Chia seeds. :) The exterior surface of the clay allows the water to evaporate readily (it evaporates fast enough to actually create a cooling affect), also, so a constant supply of water is necessary to keep the clay wet.

Slap me if I'm sounding too technical.

So, if you only have a clay helmet, you will have to mist it constantly while you are wearing it, or the seedlings will start to wilt. That's why I was mentioning the felt/towel/cheese cloth, because they will actually retain water, not just "moisture," and the clay dries out very quickly from evaporation.

Hey thanks for the great comments. Wally you sound like a real chia expert so i am going with your method. I will have time before the big day to work on it. The Burning man theme for '07 is Green Man, so is our Kostme Kult float in the Greenwich Village halloween parade.

Concerning the weight, I am used to suffering for my art, and have many very uncomfortable costume, but I will go the cheesecloth route anyway. If that works, I am making a chia moustache as well, for that I am thinking of cheee cloth and spirit gum to make it stick.