Marks disappear in 1-3 days or can be erased with water. I've done the test and use this in our studio everyday. You can use it to trace in dots and it justs makes things easier when your looking for precision in your marking.
Works on all kinds of fabric and you can see your marks on most colours and textures.
Handy for indicating where to match up pieces that fit together.
I literally use this everyday and like the fact that the marks last for more than 10mins!