Basically pack in salt and heat in oven.

Unlike annealing - because the part is almost gas tight, there is very little dimensional loss.
Also because you are packing it in fine salt - essnetially you are creating a 'lost wax' mould making method - but keeping the wax.

Essentially you are producing a one shot injection moulded part.

Ingenious :-)
Plus salt is cheap and almost completely inert.

Very clever bit of thinking.

I will be trying this at some point.

Actualy watertight vases !
Now that's something you can actually sell.