Friday morning before work, I finished cutting the top to allow for a smaller, hinged lid so that I don't have to remove/open the entire lid to put scraps inside.
After work I went to TechShop to bend up some handles and MIG weld them to the top as well as a hinge for the smaller lid. I found a cool old wingnut and bolt in the community scrap bin that I used for a handle for the smaller lid.
Here the lid is cleaned up a little with a wire brush in the angle grinder. No reason really, just piddling around.
I then shot the top and bottom with some high temp BBQ grill paint in a rattle can. I didn't put a lot of effort in the paint job as it's mainly just to keep the rust under control.
Sunday morning, I got up and started on it again. I put the 1-1/2" sheet metal screws in the previously drilled holes. Recall, these will hopefully help to give the cement something to bite into on the walls and lid. Then, I got to work putting the forms together.
I wasn't able to find "real" refractory cement locally. There are quite a few home brew recipes on the Internet but I decided to go with my own blend. I used 3 parts perlite to 1 part QUICKRETE #1102 Mortar Mix by volume. The mortar mix was suggested by an employee of the hardware store who mentioned that a lot of people use it for outdoor pizza ovens and barbeque grills. I checked the MSDS from QUICKRETE and it has a melting point ">2700 degrees F". I never was able to find much in the way of expansion/contraction rates but hopefully it will work for my purpose.
I mixed the two ingredients thoroughly. Dry at first and then added just enough water to give it an oatmeal-like texture. I realize that isn't the best example, people like there oatmeal different ways. In general, I think most people make oatmeal too runny. I like my oatmeal just moist enough where it sticks together but not so wet that you can pour liquid out of it. I mixed the mortar/perlite in the same manner: it would hold together when squeezed but no water dripped out.
The next hour or so was spent putting in a few inches of the mix at a time, tamping it evenly to remove any air, and repeating. Initially, I mixed up about 4 gallons which I thought would be more then enough but this only ended up being 2/3 of what I needed. I made another quick batch and then finished with some to spare. I used the leftovers to make a small coffee can furnace and also threw the rest in some of the plastic bowls I used for measuring.
Unfortunately, it's chilly and damp here so now I am concerned about how long it will take for the mix to dry out sufficiently to use the furnace.