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Refractory Insulation For Backyard Foundry
The Ingredients...
DIYShopTools.com - Homemade High-Temperature Refractory Mix Ingredients
The Process...
Obviously I'm building a new (upgraded) foundry for my projects that need such ability. A key component to a foundry is it's refractory. The main ingredient is firebrick that my local Home Depot started to carry recently. It's a MASSIVE savings over the usual firebrick online (which is also 1/2 the size of the HD ones) - $1.22 each compared to $30 for a 6-pack. Without taking the double thickness into account, it's 4 for the price of 1. If you do take it into account, it's 8 for the price of 1. So I ended up able to undertake this project MUCH earlier than expected. Now I just need a refractory mortar and filler. The lighter the better, as these are not the "light fire bricks". Since I'm using an old school metal trashcan as the shell, it's not the most portable size if filled with bricks. So I'm exploring the idea of using the firebrick to fully line one layer inside the foundry, with the rest consisting of a homemade refractory material that's cheap, insulates well, but is light weight. I'm currently experimenting with multiple different materials in varying amounts in all sorts of combinations. Some that I'm considering for crucible construction as well. I will post the results as well as the direction I choose. Please stay tuned.


Since my first attempts at using sodium silicate were absolute garbage - and I've seen so many people talk about how well it works - I'm going to try to give it another shot with CO2 to cure it (likely from dry ice as I don't have a cylinder or source for it). The closest location to me was sold out of firebrick when I went to get more (well, they showed an entire pallet in stock, but even the store manager said they were sold out) so I can't fully build it, but I think I'm going to make the little crucible platform with drainage hole as well as the bottom most layer of refractory. It will have fire bricks peppered throughout but not a solid layer of them, in an effort to keep the weight down. This approach will also be best for drainage should a crucible failure occur. I can also best situate the burner inlet at this time (I plan to give it a very slight upward angle to best distribute the heat inside rather than it be a lateral ring around the bottom as was the case with my previous one. I believe this will result in a more spread out heat, melting the metals more easily, and since I plan on using a significantly hotter flame compared to the forced air/high pressure LPG (liquid propane gas) burner from my previous foundry, and I don't wanna punch a hole through the side or cut out a ring on the height that the flame circles. Plus, if I plan on having the foundry split open for easier access to the crucible, I'm going to want to make sure I angle it in a way that it doesn't come shooting out of a crack at the doors. This should be interesting...