I've not heard that particular assessment of kitty litter — and tho I do understand that it's made of clay, I've not used it for oven building — sounds like a good experiment. (I do suspect that brands vary quite a bit depending on where they source their clay, and how they treat it — or not.)

My solution to the problem of crumbling inner layers has been to soak them with a mix of half water and half "waterglass," aka sodium silicate; it is used by potters to deflocculate glazes, and to mend kilns. At high temps, it fuses w/surrounding aggregate and helps hold stuff together. Available at ceramic suppliers. It's also caustic, so take appropriate precautions.

Also, if you "mist" your loaves, or squirt water into the oven to aid crust development, it will take a heavy toll on the interior surface. Alan Scott always maintained that true hearth loaves steamed themselves with water from the dough — I agree with that, and like the loaves we make without spraying.

I do use a damp scuffle to clean the oven floor, but I don't make it dripping wet. Since the steam generated by the mopping is truly steam, it produces less thermal shock to the oven dome than drops of actual water (remember that converting water to steam requires substantially more energy than simply raising the temperature of water one more degree).

All clay will degrade with repeated thermal shock, even the finest firebrick.

If you try the kitty litter approach, do take notes and share what you learn!

You might also ask on the brickoven listserve at yahoo.groups.

Hope this helps. And that you have a lovely winter/solstice/xmas there in VT.

Best,

– Kiko

I've read The Book of Masonry Stoves, and recommend it highly to anyone interested in building an indoor oven — it's a very good solution in places where climate and budget go that way. I've also built masonry heaters of the rocket stove variety (which can be modified to bake as well), so I certainly appreciate your point and agree completely. Maybe we need a new book that combines some of these stories and principles?

A masonry oven fired up just to cook one meal will be energy inefficient, as you say. But a masonry heater that is fired up to heat your home in the winter can be fantastically efficient, and that's even before you cook food in the oven compartment that might be included without having to burn any additional fuel. Some of these masonry heaters will keep a sizable home warm all day with just a small amount of wood burned. And the bread that might come with the process is a fantastic frosting on the cake.

Of course we have to be sure we're talking about the same things here. One day, hopefully everyone will know the difference between a masonry heater and a masonry oven, and will use the terms accurately to avoid confusion.

Thanks very much for your comments above; I've often felt that one must have a holistic view of the oven making enterprise, from gathering the materials, to construction, to gathering fuel before each firing, to the firing and cooking. For each firing I get my guests involved, and I guarantee it makes everything taste better!

Here's a question: I used the "Vermont Grey" clay that we have so much of around here and it seemed to work well, but I think my current oven reached it's end-of-life this year as bits of the interior started falling in. Frankly this was a minor problem from the beginning, but really only started happening during firing after three years; this is bad when my focus is pizza!

When I build again next spring, I wonder if there is something I can do when I build the "lining" (the inner layer) do make it a bit more "refractory." I've heard for example that dissolving kitty litter creates the equivalent of refractory cement; wondering if you've heard of that.

Thanks very much for your great book!!!