I like making salt/sugar scrubs, lotions, etc. for my use, and occasionally my sister or a friend will purloin something they see, so I want preservatives in them. I've gotten a lot of diff ones - Germaben II E, Germaben II, Optiphen, Suttocide, Phenonip... The idiot question is, where can I learn which one goes in what? Each has a description of what it's good for, but like, my scrubs are oils. Do I use one for oils, or one for water since my wet hand goes in it? Is there a rule of thumb, like, this one's best for soaps...this for lotions, etc.? Thanks~