Lost wax^M^M^M PLA casting

After Jeshua tried lost wax aluminum casting but with 3d printed PLA I was sceptical if this was within the possibilities of a DIY project.
The equipment he used looked like it was only feasable if you worked at a steel melting plant or something.

Now David Knaack posted some photos of James Harr and Brandon Norris of the Omaha Maker Group doing the same thing but a way more low-tec way. I'm quite impressed. (Photos below)

 And yet another such casting. This time by David Knaack casting a RepRap filament drive gear from aluminum.

The process is:

1. make a positive master model (here a 3d print)
2. carefully cast plaster around it. Avoid trapped air.
3.  place in a furnace to get all remaining water out of the plaster and burn off the PLA.
4. slowly pour molten aluminum
5. wait for it to cool. Expect the aluminum to shrink

• first posting that started it all
• second such posting
• Omaha Maker Group
• third one. 
• Wikipedia "lost wax casting"