Hokay. Here goes. Fair warning, this is theoretical, untried, untested and as yet unmade, even in prototype.
1. Make a mould of your face. Plasticine works, liquid latex of many layers probably works, if you support it with plaster strips. Either way you're going to wind up spending time with drinking straws up your nose for the sake of air.
2. Mix up some plaster of Paris or something similar to make a cast of this. You'll need to support the mould during this. A trough of sand with the mould settled into it will work so long as it's strong enough not to cave in.
3. While that's setting (give it two days or so, it'll be quite thick) make your Rorschach inkblot pattern. I suggest using ink-blots which will all overlap at critical points such as over the eyes, mouth and nostrils. Print out a bunch of the images (more than 4 or five will be annoying as HELL) and trace them onto overhead sheets or transparent sheet protectors, putting lines of the colour as hatching over the internal area. Don't bother with the really fiddly bits such as small holes. They'll just get too annoying.
4. Overlay these sheets and place a blank one on top. Onto this you're going to trace all the various sections of the others where they overlap, and where they don't. If an area is occupied by blots 1 and 2, but untouched by the others, that's one section and so on. Eventually you'll have it looking like a puzzle. Now you need to label sections which have different combinations of ink blots, such as all the sections with only ink-blots 1 and 2. Or just 1. Or 1 and 4, etc. Mark all the areas with each combination the same.
5. As you have a pattern, it's time to go back to the cast face. Cover it first with a sealant such as liquid latex, leaving holes to breathe through and eye slits for sight. These can be covered with black gauze so they're permeable but invisible.. relatively. A layer of insulant comes next. Cotton works, if you use several layers of fabric. Polyester padding does too but be careful because you don't want anything which is adverse to temperatures around the 40 C mark.
6. You'll need some material like what they make the heating strips across car rear windows out of. Not a clue what you'd use but hey, this is theoretical. Cut pieces of this material to fit the face and according to your earlier pattern for the Rorschach blots and wire it up according to the code of what you need for each blot. Parallel circuits are your friend. Attach the wiring to the mask along with the pieces of resistor and seal it, with a battery pack and mini-computer/switch board to be held in the pocket. If you're really cool you'll make a glove out of that.
7. Dye a batch of stretchy fabric with heat-reactive ink which goes black at say, 40 C and then attach it over the mask. With fabric you don't need to worry about the holes for breathing though you will for the eye holes, so just secure it around the outside and let the gauze show instead.
8. The back of the mask would work as a continuation of the fabric. Just sew it on and attach an elastic strap to either side of the mask, then another from the top to join them in the middle. This goes under the fabric back.
Voila! Should work. Maybe. Wouldn't weigh to much if you did it right, and infinitely more difficult than what that guy makes with just fabric.
[sub]To be fair, I once designed an armoured suit which instead of actual armour had harnesses and food packs for live kittens on the basis that no-one would ever attack you if you had two dozen tiny, mewing cats strapped to your body... so this may just be another crazy idea.[/sub]
