So I wanted to order the blank key caps for the kinesis advantage.
However since it appears to cost more then 100 $ to ship them to europe I decided to wait for somebody from the US to visit and bring them for free.
Now I did not want to go two years without the blank key caps so I did use a sharpie to paint most of the caps black and
used fixing spray for paintings and spray to make shoes waterproof to prevent washing the color off with sweat like it has been a problem when I tried this in the past. So far I have no black fingers and the caps are still blank like they should be.
Everything I used is soluble in ethanol and thus the whole process is reversible by using alcohol to make the prints on the caps visible again.
I am sure that the effect is not permanent and will wear with time. But when that happens I just repeat the process until I have my blank caps.