it looks a bit like paper mache but to me i dont think it would be sturdy enough to be able to take a few pictures in (im assuming you took more than one and had fun with the picture taking i mean how could you not lol) i mean ive made a few masks including ichigo's full hollow when he has the horns grimmjows and tia halibel's and szayels (szayels was the most fun because i used my actual glasses i wear everyday and trust me clay plus glasses plus being baked in my kiln i could get the clay off so i had to wear szayel's mask/glasses for 4 months until i got a new pair lol) but all of those i used either clay or i shaved wood into its shape and that doesnt look like any of that
I think that he used a material as PVC (or similar) you can buy a panel of PVC,cut to get the right shape and bake it in the oven! it's a bit diffucul because pvc gets very hot!(so working is not simple xD)
you can buy a panel of PVC,cut to get the right shape and bake it in the oven! it's a bit diffucul because pvc gets very hot!(so working is not simple xD)