Just finished up the last of the sheet metal work. The sheet metal was added in an attempt to reinforce the microwave shell and wave guide already in place.
Structurally, the additional sheet metal acts to protect the wave guide from being dented or damaged. The wave guides dimensions are important, and I didn't want to change it from how it was originally designed.
I am using a microwave that was built in 1984. Microwaves as a consumer product was relatively new at this time, so I wasn't too sure they had all the kinks worked out of their design just yet. The added metal around the magnetron and waveguide hopefully will keep all the RF within the machine, and not astray throughout my laboratory.
The sheet metal surrounding the magnetron will function as an air duct to keep the magnetron from overheating. A blower will be mounted on the outside of the case and directed through this duct.
With all the sheet metal work out of the way, the next step is to add the insulation and the outer shell of the machine. I am using a combination of water glass, perlite, and broken up pieces of ceramic from things like old tiles and old coffee mugs.
I made the water glass this afternoon by mixing sodium hydroxide, silica gel, and water. It's simple to prepare, and if done right, the sodium hydroxide provides ample heat and you won't even need to mess around with a hot plate. I've done it enough times that I simply premix the lye and silica in a pyrex bowl, quickly pour in the water and put a very loose fitting lid on it and make my escape. Return in an hour to a finished product! Done wrong and you come back to a rock hard mess, or an incomplete reaction. If anyone's interested I can elaborate but I'll leave it at that for now.