Let's just assume that I ordered a bottle of Stop Rot and decided, against the directions to pour it into a spray bottle I had in the cabinet. I set it aside so I wouldn't confuse it. At the same time, I filled a another spray bottle with water to use in cleaning up and during mounting. In a rush, I sat that bottle in the same cabinet with the bottle of Stop Rot. Neither bottle was marked. Now just how do I tell which one is which. And before you answer, be careful. Obviously both bottles are colorless. I smelled the bottles; both are odorless I tasted them; both are tasteless I checked the pH; both are 7.0 neutral Any other bright ideas would be appreciated. And before some genius tells me to mark the bottles, that's already on the list.