Gidday from New Zealand

[AndrewT]

Hey I'm Andrew T from Rotorua, New Zealand.

I've become obsessed with wood fired ovens.

My wife bought me a clay pizza oven not long before Christmas. After reading this and other forums I have modified it so it holds its heat longer.

My plan is now to build my own version 2 oven from scratch. Thinking about using the homebrew mix over a sand dome.

Lots of the materials I would like to use are hard to get in New Zealand (refractory cement, stainless needles, fire bricks, etc).

I've seen the guy on youtube who made an oven using a pumice / portland cement mix so thinking maybe a layer of that over the homebrew and then ceramic blanket: https://www.youtube.com/watch?v=0FzuScb28gs

I've seen it written on here in many posts that the homebrew works as a castable but might cause problems after 5 years. Wondering where this has come from and if anyone has an older homebrew castable that has had a long service? I suppose it depends on how much use it gets and other factors (e.g. is it a cold climate, does it stay completely dry).

[david s]

Can't say about the longevity of home-brew castable, but it's so cheap to make that a rebuild after six or seven years wouldn't be so bad. Use firebricks for the floor, home-brew won't last for a cast floor of it. A dedicated castable refractory is certainly stronger but way more expensive. Don't use the pumice/ cement mix on the inside, it's not nearly strong enough to withstand abrasion wear, and not dense enough to store heat. It's fine to use over the inner layer as an insulator provided it's a pretty lean mix (10:1)

If making your own home-brew castable try to get some fine polypropylene fibres (used as reinforcing in concrete), to add to the brew. These fibres burn away at 160 C and leave a network of mini pipes that steam can escape through. Don't use poly rope, the fibres are too thick to melt at 160C (i've tested them) You only need about half a handful for every 10 L of mix, but mix for longer to get them to disperse.