Chaudywogbaaga

My old furnace is getting a bit worn from being exposed to the elements all the time (it’s too big to move indoors easily). I will be fixing it up but I wanted to try a different form factor first. In addition, I wanted to make something with a smaller internal volume to see how much faster I could get it up to temperature. I also got an old metal mailbox that I’m making into a forge like one I saw on TV one time. That’s more of a side project.

Hit the “More” for pictures.

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Here I punched a hole, slightly off center that will be the port for the burner. I just drilled holes around the perimeter of the cut out and then used a grinder with a abrasive cut off blade to cut between the holes. It wasn’t a pretty job, but I don’t need it to be.

I inserted a metal vent pipe in the hole. At this point its just for fit. The metal pipe could have just as easily been cardboard since it will not stand up to the heat of the furnace. It’s only there for a form to pack refractory around. I couldn’t find any cardboard of a diameter that I wanted. I also could have used foam and just burned it out. In the end, either of those choices would have been better because now I’ll have to get the metal out somehow. . . Oh well.

This is the lid of the garbage can with the handle removed and a short section of pipe in it to form the tweer (or the vent hole if you’re not familiar with the terminology).

I used a Sonotube to create the form for the interior void of the furnace. This will burn away in the first heating of the furnace.

As it looks in position.

Looking through the burner port. Notice that the burner port is not centered on the can or the Sonotube. This will help to create a vortex of swirling gas around the crucible for more even heat. The little stands around the bottom are to allow the floor of the furnace to be one solid piece on the bottom. I’m a little worried that there won’t be enough insulation on the bottom but I won’t know until I’ve tried.

I wanted to make a solid and durable hotface just around the interior of the furnace but insulation is really important and the Mizzou that I’m using for refractory is not a good insulator. So what I’m trying is straight Mizzou for the hotface and mixing Mizzou with perlite for insulation on the outside of the hotface. It probably won’t be a lot but hopefully it will be enough.

The hotface goes between the Sonotubes and the Mizzou perlite mixture will go between the larger Sonotube and the walls of the metal can.

Reenforcing the lid with chickenwire. There is some cement bits on the chickenwire as it is left over from an earlier project. That may be a mistake if the cement ends up weakening the lid. If it does, I’ll just have to re pour the lid.

Parts preassembled for fit.

The refractory manufacturer says to add 5 pints of water to 55 pounds of mix. I could not mix all the refractory with that small amount of water and ended up using far more. As a result, I’ve been letting my furnace cure for longer than the recommended 24 hours.

Always protect your skin and lungs when working with materials like this! Gloves and respirators are essential.

I mixed the refractory in a 5 gallon bucket. I would not recommend using this method. I did it this way because I am used to it from my days installing tile floors but would have done better if I used a wheelbarrow or a cement mixing pan. I’ll be keeping that in mind for next time.
I would recommend adding half the proscribed amount of water first and then the refractory mix. This prevents a lot of dry mix being left over on the bottom of your mixing container. (Another hold over from tile installing.)

I didn’t have the hands to take pictures while I was working with the refractory. It works like wet sand and not at all like concrete even after adding about three times the proscribed amount of water.

Well thats all for now. I’ll post more when I fire it up.

To see the furnace in action, click here.