Saw The Invisible Man for the first time recently and I was really impressed with the special effects. For a film from 1931, I found the movie fascinating and even more entertaining knowing all of this was done before computers. I don't even think they even had a category for special effects yet, did they? So, how did they do it? The breadth and scope of what they did for its time is nothing short of remarkable. I'm really curious as to how they managed the invisibility for its time, particularly when his head is not fully unwrapped.
Basically the same as green (or blue) screen. But using black instead, and matting him into the BG shot separately: http://en.wikipedia.org/wiki/The_Invisible_Man_(film)#Special_effects