Or not. Well, that didn't go as planned. The mould was pretty much a disaster. Loads of air bubbles in the plaster; half the mouth was obliterated, for example, and bubbles elsewhere resulted in what looked like huge bubos on the latex castings. I managed to bodge several repairs, but not very effectively. And the method itself is lacking. It's very difficult to make decent latex skin castings because one needs to keep the mould closed with the armature inside. Carefully and gradually pouring latex into the mould halves before clamping them together helps, but is far from perfect; and getting the liquid foam mixture to fill all hollows inside before it froths up is also very unpredictable. This latter factor is vital because it is necessary for the armature wires for the jaws to be thoroughly embedded in the foam, otherwise they detach with handling from the latex skin thus making animating the mouth impossible. The whole process is fundamentally nigh on impossible to control effectively. In an ideal world I would make the heads from foam latex or, a distant second, silicone rubber.
Nevertheless, despite all these caveats, three attempts at casting have seen successive improvements. Below you can see the third casting, painted with PAX paint and modelmaker's acrylics. Quite apart from the deficient casting (all those semi-bodged repairs), it's not a brilliant paintjob (I've put off the eyebrows as they're a bastard to do, one tiny slip and you're fucked) and the eyes are just unmarked white beads for now, but it's showing promise and is a useful testbed.