How to keep my pizza stone from smoking? We have 5 year old a pizza stone that use to make homemade pizzas, pita bread, etc...

For as long as I can remember every time we preheat it in the oven (before adding any food on it) it produces a huge amount of smoke. The oven is clean.

Depending on what we're using it for the temperature varies, but on average I'd say ~400°F. I'm not 100% sure of the stone material, but I would guess Cordierite because it looks similar to this stone.

Is there anyway to prevent the smoke?
(1) Wikihow suggests "As a last resort, soak your stone in water," and also "Baking soda is a sodium bicarbonate and is great for cleaning off dirt and grease," and lastly, an a one-shot hail mary, "Using The Self-Cleaning Function."

http://www.wikihow.com/Clean-a-Pizza-Stone

(2) Caveat: I've not tried any of these methods myself.  I bake pizza on a flat cast iron pan, which I use for everything else.  It works fine, you can put a bit of oil on the bottom of the pan.