Some background on myself. I've been a graphic designer for almost 20 years, started sculpting more seriously about 10-12 years ago, and started carving / building for a mascot company about a year and a half ago. With that said, although I do understand mold making and vacuum forming processes, I have no experience in either. So, I build or sculpt everything and that's where the process usually ends.As mentioned, I built this costume primarily out of sintra (PVC foam board) because it has some flexibility, is easy to work with, and can produce a nice finished surface.All elemets of this costume were approached the same way - photos, measurements, 2D drawings, scale, proportions. I used Adobe illustrator to hash out linear drawings of the helmet. Once I had the correct size of the dome, I was able to start. After a couple failed attempts at creating the dome with plastazote foam (making wedges to form the dome) I decided to carve it the old fashion way and simply used pink insulation foam from Home depot. Once I completed the dome, I began building the helmet using the antenna mount as my anchor point. I used a heat gun to shape and form the sintra, and glued layers to create the details throughout the helmet. After a few revisions ( the dark green concave section wasn't deep enough and I had to redo it) the helmet was ready for bondo glazing putty. I use this to fill the seams and rough spots in order to achieve a seamless plastic molded look, much like a Lego minifigure.