Since I've been vaping and trying new liquids I couldn't figure out how to label my things to keep up with what I've done. I've used a sharpie which always ended up coming off and I was back where I started vaping a coffee mixed with menthol eww. I got an oil based paint sharpie from an office supply store that said it worked on glass. Turns out it worked really well and are not expensive. The only colors I've seen are white,gold, and silver. Just thought is share for someone else who may have the same issue.