Making a custom mask The plastic is the same stuff used to cast dentures. Jerry Stugen (the former owner of Stan's Skin Diving in San Jose) used to make the "bone" masks by: make a mold of your face (the negative) cast a plaster replica of your face (the positive) mount the positive on a piece of plywood horizontally level the eyes of the positive modify the positive slightly in the cheeks and under the nose to more closely follow the contours of the underlying bone rather than the soft tissues above select a one-piece tempered glass mask insert set it on the positive, making sure the glass is level vertically and horizontally use modelling clay to build up a mold for the plastic resin construct the nose pocket using thin sheets (1mm) of clay to coat the nose and surrounding cheeks construct the inner mold that will support the glass construct the mold on the front of the glass construct the outer mold for the skirt add mounting points for the mask strap at eye level make sure the glass is level vertically and horizontally pour the resin up to the level of the mask rim allow it to cure construct the outer mold for the nose pocket with a hole at the tip add it to your cured mask pour the nose pocket allow the mask to cure fully remove the mask from the mold use a file or dremel tool to remove all the flashing drill the mounting points for the mask strap paint the outside of the resin with black tool dip to block stray light (maybe, you could mix very fine carbon black into the resin instead) A few notes: I don't know what is used for a mold release where the mask touches the plaster positive. I assume, the glass must be very clean for the resin to bound to it effectively. I don't know, if the resin will bound to itself when you pour the nose pocket. A possible work-a-round would be: construct the mold with a nose pocket, pour up to the rim, wait for the resin to start setting then pour the nose pocket; but the mold would be slightly more complicated. Always keep your mask in a padded rigid box when not wearing it, they are brittle.