You should have seen the look on my brother's face when I placed a handkerchief on top of his school
book and dumped ink all over it! Of course, it soaked through the handkerchief instantly :-)
It takes about 15 minutes to vanish.
If you perform it on a silk, you can see where the
ink was if you hold it up to the light, but after 20-30 minutes, it's COMPLETELY gone.