Wait, do I understand correctly? You were going to pour the oil and lye solution directly into the bathtub or sink? Or were you going to place the bowls into the tub while you mixed - to catch any stay batter that flew out?
If its the first case, then it sounds like you would benefit from some more research in lye safety, and the process of making soap. Let us know, and we can supply some YT vids, plus reading several sections in the beginner's section of this forum. Making your first batch takes preparation.