ok well obviously stainless is the second best other than glass.I don't get why everyone is against copper. Look at your local building codes and you will see that the majority of pluming is copper and guess what water stays in it. Copper has been used in pots and is used just now it has a stainless coating on the food surface but the flame side is still exposed, guess what there are fumes coming off the copper then, and it would be the copper smoke that is harmfull. When using copper for the stem is not even going to reach a temperature where it will be released. As for the oxidation if you clean your hookah like you are supposed to then you will not have any issues with copper oxidation that may effect you not to mention that will not travel through the smoke any way. so unless your swallowing pennies all the time you will be ok with a copper stem.