@_thegeoff How are you going to remove the print from within afterwards? Also am curious why would you want the mould to be out of concrete -- it's neither flexible (like silicone) or easy to form (like casting sand).
@_thegeoff Ah, and it's obviously convex (because otherwise how would you extract the final product).
@robryk It's a nasty set of compound curves, took me a few hours simply to work out where the seam line should run...and it's very not linear...
@robryk Also, even if the print doesn't properly release, a blowtorch outdoors is an option.Not quite lost wax technique, but comparable.
We had a failed cast earlier in the week - mould broke on removal cos my concrete recipe sucked, but where it worked it was detailed enough to show the 0.3mm print layers.
@_thegeoff I'm really curious how uniform will the thickness of the glass be. (I know glass bottles are made that way, but I always assumed that works by careful preforming of the hunk of molten glass that's blown up in the form.)
@robryk The print has been coated in a release agent - petroleum jelly, which I'm assure by my colleagues works. And it needs to be concrete as it's going to be a large blob of molten glass inflated by compressed air, so needs both heat resistance and a lot of structural integrity.