Here you can see a video of him working. You can quite clear see how he works.
Step 1: Clear,cut,tear and Stick
Start with a clean window and cut/tear the tape to the size you need. Stick it close together in one direction.
Cover the whole window, for the size you need, with one layer.
Step 2: To Draw or Not to Draw
If you're an artist like Max Zorn you can just start cutting out areas which have to be lighter but I found it a bit easier first to draw a light sketch after a photo. For this one I used a famous artist portraiture, which I mirrored for composition's sake.
Step 3: "Cutfinger" He's the Man With the Cutting Touch.....
After the tape sticking it is time to cut away parts where it has to be more lightened and more tape crossed over the parts where there has to be more shadows. The way to do it is showed best in the original Max Zorn video. It takes some practice but if you make a mistake you just put another piece of tape over it.
Have fun making art and please show it here when you made one. I'll use this Instructable in my classes.