Wood fired snake kiln cast chimney.

In this seemingly never-ending saga of the building of my kiln comes the next chapter.

I have to build the chimney next. I have decided on a homemade cast type construction. There are many challenges but I will go into only a couple. I have figured out the first problem of how little concrete I can use and still have the mix set without risking spalling during the firing. The chimney won’t reach the same temperature as the inside of the kiln but it is going to help me sleep better knowing the concrete in the mix is kept to a minimum. The mixture of one concrete, one mortar and 3 or 4 crushed soft fire brick set up fine. The crushed firebrick ratio is a little unclear as I only measure it before I crush it. I ran out of cement this last mix and cut the concrete down by about 25%. That pour isn’t fully set yet so I don’t know about the hardness of it yet or if it is going to hold up in compressive strength. If not it will be a disaster as it is at the bottom of the chimney stack and will require a tear down and re-build.

Another challenge I have is the form itself. I don’t want to use pre-made round forms because of cost and the amount of material I can mix up at once isn’t all that great. It works best for me to cast about 30 cm. vertically each time. The challenge is to keep the chimney plumb with so many small casts. I figured out a method yesterday wherein I will set four inner vertical plumb forms. These will be forms I will screw the actual forming material to. By pre-setting them I can make sure they are plumb and they will control the vertical plumb. Pictures are worth a thousand words so when I get them set I will post some.

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