No need for all the hard work to make a stealth juice, here is what you do : when packing your carry on bag, pack some Kleenex or a handkerchief. In one and you have said Kleenex or hanky, in the other, your ecig. Take a drag, like normal, and with the hanky balled up in your other hand (hold your hand like you are holding a roll of quarters in a fist) press your hand to your mouth and exhale. Keep in mind, this works best when your hanky filter isn't balled too tight, but try to make sure as much vapor comes into contact with as much material as possible. To practice, or demonstrate, sub your fist for a toilet paper roll, stuff tp or napkins in it and BOOM! A stealth tube (or a "dirty stick" to potheads). It takes all the visible moisture out of the vape cloud, and doesn't stain. NOTE : I DO NOT RECOMMEND TRYING TO PACK/TAKE A DIRTY STICK ONTO A COMMERCIAL PLANE! X-rays may show it as a suspicious container or incendiary device