Hello! Benjamin from Brother’s Campfire here!
Yesterday, I put together a Campfire, and today I spent a lot of my day lining the inside. From prior experience, I learned the bricks that you purchase at Lowes or Home Depot break easily when heated.
Most folks might not notice if they only have a fire every once in a while, but here at Brother’s Campfire, they are a regular occurance. Concrete does not do well under fire.
Firebrick mortar is expensive, and I am not a mason, so I web searched solutions. There are numerous recipes for firebrick mortor out there and many of them contain run of the mill concrete. While not a scientist, observing has shown me that is not a good idea long term.
I began looking more specifically on blacksmith sites and also in the realm of pottery.
What I discovered is that clay is abundant in alumina which has a high melting temperature. This led to a rabbit trail of making bread ovens with a mix of straw for support.
Bricks can be made this way, but I would be better off with concrete than straw. I build fires above 1400 F that can melt an aluminum can in seconds and it would turn the straw to carbon rather quickly.
So I turned to sand. Potters mix sand in their work for support, and it is hard to melt or burn sand for the most part.
That was easy. A quick walk to the end of the street resulted in a bucket full from the snow plows. A recent rain had washed a bunch in a handy pile.
The clay required a little more work. About a tenth of a mile away was a tunnel that had plenty of clay.
Breaks are for the bright, and those with gall bladders. I had some playing in the mud to do and nothing was going to hold me back. I mixed me some muck and started slathering mud.
It did not work well so I mixed it to a consistency of a good mudball for slinging and slung it. After it set a bit, I smoothed it out.
Firing it was my number one priority. I wanted a Campfire, yesterday.
I figured the most heat would be at the bottom so I layered it with wet straw to slow it down and built a rounded fire to dry out the edges.
After about an hour of slow-burning, the side walls seemed to be getting a lot drier. I raised the temperature by adding some real fuel.
Having never done this, I did not account for up to 15 percent shrinkage and there were quite a few cracks. The interior is very hard and retains heat so I am ok with it for the time being.
For anyone wanting to try this, the clay needs to be completely dry before you fire it. Oh well, live and learn.
What is important to me is that even full of logs, the bricks on the outside are not directly exposed to the fire.
The mix was free and I would have been very sad if a store-bought variety had cracked in such a way. I can patch this up any time I want now.
Today’s adventure was playing in the mud.
What could be better?