Kitty Litter Clay Oven

Each Christmas my family does a prank-gift exchange, a lighthearted parody of the rampant consumerism that follows it. This year, I found my gift idea on the pizzle: Kitty Litter cornbread. I'll do a write-up about that later, but while I'm on the topic of kitty litter...

After Christmas, I continued my descent into mental illness found another use for (traditional) kitty litter. Ovens! Last month I bought a book on how to make a wood-fired earthen oven, or a mud oven, and wanted to make one over winter break.

Like an oven, but with a face

So, on one hand it's kitty litter, but on the other hand it makes sourdough. Aussie is naturally very conflicted by the consequences of this book. I should probably explain why the heck kitty litter had to be involved.

The type of oven described in the book is built from clay and sand--adobe style. The author suggests you dig about 5-10 feet underground to get to pure clay, and then mix it with builder's sand to create a mud that you can shape the oven with. Unfortunately, our backyard is blessed with a whole lot of silt, which is a bit grittier (and less sticky) than clay.

Notice the retaining wall right behind it

Even about 6 feet down, I was getting minimal clay. Also, I hadn't exactly explained about the project to my other family members, so they were a bit concerned when I randomly started digging a giant hole in the yard.

I didn't want to go much deeper, because this is the part of the backyard immediately facing the giant hill. Combined with the rain and my discovery that it seems to be silt all the way down, a more massive hole might not help our house stay on the top of the hill.

Notice the exposed sprinkler pipe.

As a small aside, for the past week, I've come in to work with dried muddy shoes. When one of my coworkers asked why, I told him I'd been digging shallow graves in the canyon again--can't have any witnesses. I'm pretty sure HR will chat with me one day.

This is the shiny new wheelbarrow that made this project a breeze.

Anyway, with the super silty soil, I wanted to fortify it with a bit of clay just to make sure the mud oven wouldn't collapse immediately. I drove to a ceramics store in Santa Ana, and it was closed until after the new year! The other sources of clay were super expensive (over $25) for a small amount, and it didn't feel right to purchase a block of clay from Michael's and immediately dump it into the mud.

Enter kitty litter.

You probably know already that the cheap kitty litter is usually just clay and some baking soda. I poured a container of the litter into a bucket and set it outside in the rain. Rainwater has carbonic acid (dissolved CO2) in it, so I let it react with the baking soda to make a purer clay. Also letting it soak a few days made it a bit easier to work with.

I don't have many pictures of actual construction. It was pretty much the messiest thing I've ever done. Let that sink in. The messiest thing JON has ever done. With mud everywhere on me and around me, I couldn't handle a phone much less take pictures with it.

The only picture from construction I snapped was of the sand form that formed the inside mold for the mud to go around.

From there, I mixed the mud, and basically formed an oven around the sand form. The sand I covered with wet newspaper for when I needed to dig it out. That let me know where the sand ended and the mud began.

I cut a door out of the mud, and started digging out the sand, and one incredibly messy day later...


The pictures make it look like the oven slumped a bit, but that didn't happen. The base walls are just incredibly thick, and the upper is a bit thinner. Inside it still has the same shape.

In order to make the oven a bit stronger, it has to dry out, and the quickest way to dry it out is to have a fire in it for a day or two.

Right now, it feels pretty sturdy. It's a tad crumbly if you scratch it, like very old bricks, but it seems to be holding out at the outset. It hasn't collapsed yet!!

The fire is sort-of a pain to stoke right now. I'll figure out a system that works, but I've got the big job done. Once it's completely dry, it'll supposedly retain heat much better, and then I can heat it up and cook about 4 loaves of bread, and slow cook something overnight.

So what did this oven need to get built? Well, just a few cinder blocks, bricks, 6 bags of building sand, wheelbarrow, a 12-pack of beer I had to buy my father to make him okay with this, and most importantly, the kitty litter.