This is a video made by Andrew Ainsworth - the original designer of the 1977 Star Wars Storm Trooper helmets. A few years back, he won a legal battle with LucasFilm that allows him to continue to manufacture replica helmets for fans.
While the video is 13 minutes long, but it's amazing to see this guy go from a plastic dome, plasticine, and a ruler - to a finished movie prop. Wow. 4
Also, vacume-forming plastic machines are magic.
Found via: TR.