Sorry, I always forget about this site! Two years later... :) here I am!
Wet method (versus powder) is where the final product is wet. Not to gross you out but it's kind of like semen. Salty and coagulant (gross huh?). If one wants to make the powder thye have to have the proper equipment for heating the precipitate at high temperatures. With wet method you can produce the precipitate using food-grade lye (to raise pH) and hydrochloric acid or vinegar (to lower pH).
Heavy metals only present themselves when pH goes over 10.78 otherwise they are not in this "realm" so to speak. I only trust myself so I know what's in it. Also, dead Sea Salt apparently has no heavy metals in it, so even if you go over 10.78 there will be no recriminations.