After a good 24 hours of vaping I'll get up in the morning and just pull all sorts of funk off my tongue. Sometimes the taste of what I'm vaping will even get a little funky until I use the tongue scraper. I would describe it as an oily or petrol taste. I always thought it was a myth that vaping leaves residue on the tongue but I was wrong. Anyway, I've only been using a scraper for about one week but I highly recommend it. I also experience an immediate increase in flavor after using it.