Aussie Oven Upgrade

[juddy]

Greetings from South East Australia.

I have been lurking around this site and others for years now, however this is my first post. My interest in Wood Fired Ovens first started around 7 years ago when I was inspired by the Russell Jeavons book, "Your Brick Oven" to build an oven to his design. What resulted was an oven built of recycled red clay bricks on an uninsulated slab supported by Pine stumps. The dome of the oven was very lightly insulated and would get to hot to touch. For all the 'errors' I made with this oven it still worked a treat and resulted in about 6 years of pizzas, roasts and bread. And whats more, It didn't collapse and the pizzas weren't full of mortar! I was so taken by this little oven that I also helped around 5 friends and relatives build theirs!

The Wood Fired bug had well and truely bitten though and deep down I wanted to try and build a higher spec, bigger and more efficient oven. I was greatly impressed by the Rado Hand ovens of traditionaloven.com and ordered his DVD. Before i knew it the location had been cleared, the ground slab was poured (all by hand), and the concrete block supports for the insulated hearth slab were laid and concrete filled. The form work for the hearth slab was constructed and the insulation set before the concrete hearth slab was poured (again by hand).
More to come...

Juddy

[juddy]

Greetings again.

The next step was the oven wall and vault construction. I had acquired the firebricks for the dome at less than ½ the price that most retailers were quoting. It pays to ring around. I needed around 230 firebricks and had been quoted up to $4.40AUD per unit!!! Calcium Aluminate Cement was used for the bonding of the firebricks. The firebricks were a joy for a novice brickie like me to work with. They were relatively ‘true’, and before long the rear and sidewalls were completed. The firebrick walls were then supported from the inside of the oven (by formwork) and the concrete cladding was poured for the sides of the oven. This in turn gave me the base to start building the vaulted roof of the oven.

The oven has a vault height of 480mm, width of 860mm. There were 4 full brick width arches, and one ½ brick width arch. Each arch was made up of 14 bricks. The oven entry arch was built out of 9 50mm splits resulting in an entry height of around 300mm.

There’s still more…

Juddy

[brickie in oz]

I think you must have had the plan upside down, the insulation is supposed to between the oven hearth and the concrete slab.

[chidding]

Originally Posted by brickie in oz

I think you must have had the plan upside down, the insulation is supposed to between the oven hearth and the concrete slab.

Agreed..

i really think you should read the pompeii plans available on the forno store (free)..

Surely it makes logical sense though right? insulation next to the hot part?

[juddy]

Howdy

Interesting comments that sent me scrambling for my DVD of oven plans. The DVD contains images of 2 types of vault ovens being built. Both a very similar in design. I then read and re read the instructions that are on the disc. It would appear that I have placed the insulation in the right place. These ovens would appear to be on the high side of the thermal mass scale. So the idea was that the vermiculite would insulate the large mass of the fire brick base, and the concrete hearth slab from the void below. The entire oven has the same wall/floor thickness i.e half a fire brick then either concrete cladding/hearth slab, and finally this entire thickness is insulated. If the insulation was between the fire brick base and the hearth slab wouldn't I miss out on all the thermal mass of the hearth slab?

Cheers

Juddy

[brickie in oz]

Unfortunately most of the heat will leak out of the oven via the concrete slab and down through the slab support.

[Karangi Dude]

Hi Juddy,
You are correct in the way you have the insulation that is the Rado design.
I believe the Rado ovens are more for bread baking than the Russell Jeavons ovens.
I also have a copy of Russells book and have read a lot about Rado ovens, I wanted a more versatile oven so I went with an oven that would get up to heat rather quickly and hold heat long enough to bake. By comparison you may find it hard to get the Rado oven up to pizza temp because of all that thermal mass but it will be a good oven for baking.

Al, not quite true the insulation under the hearth is to stop the cooling via the void under the slab, the Rado design oven has an enormous amount of thermal mass and is supposed to hold heat for a long time. Most heat leak would be in the walls and above the hearth not so much from below, remember the hearth does get a lot hotter than the rest of the oven.
These type of ovens take a lot to heat up just like the Alan Scott designed ovens but they are great for baking.
Al, your oven is unique in that it is a barrel /vault oven with the insulation of a igloo type oven best of both worlds.

[juddy]

Hey Doug

That makes sense to me. I still have the original oven, and it will be great for pizza nights where you want a quick fire up. The Rado oven will be used for mainly baking bread. Part of the fun of this new oven was to build an oven that is at the other end of the spectrum to the original. One is a dome, one a vault. One secondhand clay bricks, one firebricks. One poorly inslulated, one highly insulated...

Once the oven is finished curing I will be able to compare the two effectively side by side.

After a curing fire the other night the dome temp in the new oven was around 170 degrees C. 48hrs later and the dome temp was around 90 degrees C. So I am hopeful that the greater thermal mass and increased insulation will create a great baking oven.

Cheers

Juddy

[Karangi Dude]

Juddy,
Like all ovens it will take a fair few fires to drive out the moisture so take your time and see what happens.
My oven holds heat for days if I get it up to pizza temp on Saturday night I can bake Sunday arvo and still be cooking slow roasts and stews Tue / Wed.
Yours should even hold heat longer with all that mass.

[juddy]

Hello again.

Once the oven vault and entry was complete I could clad the exterior of the oven in concrete. The forms were built out of melamine and concrete reinforcing was used throughout. Again all the concrete was hand mixed and poured. Once this was finished the brickwork surrounds could begin.

Now a brickie I am not! I found this part of the job extremely hard, and its fair to say that I’m a little disappointed with the results. All along the exterior of the oven was going to be finished in a ‘rustic’ style and thank god for that. Because now some of my dodgy bricklaying skills can be passed off as an attempt to create that ‘rustic’ appearance!

Still more…

Juddy