[ruonis55]

I'm curious about the ink, how long does it take to disappear? in the youtube videos it says 3 weeks

The place you buy has to have some sort of description of the ink and say in how many hours it disappears. If it disappears in 3 weeks then you are screwed. It should disappear in 24/48 hours or even faster. If you don't know or there is no information about it, just print the example label and set the timer to see in how many hours it disappears.