Ernie Higgins made original mask's that went through the following process. A meeting with Ernie during which he explained the entire process. How the fitting would go and then how he went about fabricating the mask. This was a custom, full face molded mask. The molding process involved lying down in a prone position face up. Ernie then chose an old dress shirt box which had an oval that closely approximated the relative shape of the head. A womens stocking then was placed on the head, and over any hair somewhat like a shower cap. Ernie then applied vasilene to the exposed area including the face. He placed two cloth pads over the eyes and used the aforementioned vaseline again to seal the edges. He then gave two or three straws for the mouth to breath out of. He then began mixing plaster of paris, and filled the box. Once this had firmed up he removed the box which now had a negative likeness of the face, During fabrication time he made a positive mold by pouring more plaster into the negative cavity and creating a 'mold' of the face. He then began a process of laying alternating layers fiberglas cloth and fiberglas resins to create the mask cutting holes etc. This was finished off with a coating of smooth resin.

"The Man Behind the Masks" - a film by Jerry Kelleher
https://www.youtube.com/watch?v=JLtkdriOAFY