Rammed earth base.

[dmun]

I think I need to use a form of sand on something similar to shape the oven, as mine is going tobe quite low.

Remember - clay shrinks a LOT when it dries, and sand doesn't. You're going to want to dig out that form before the lengthly process of drying out that much clay.

[wood-fired]

I live quite close to you on the wiltshire/somerset border and we specialise in both wood-fired ovens and rammed earth, part of my landscape business. I'd like to know how you get on with your build, or even come and see you. I'm one of the founder directors of EBUK, set up to promote earth as a resource and have done a garden in Bath using only what we dug out of the ground, both clays and stone. spacemagic garden : projects p3
yes, ALL the stone and clay came out of the ground in lower Weston, Bath.
The rammed earth we used was made up from the friable clay, crushed concrete, grit sand and a small percentage of white cement. To adapt this to your project, it might go, clays 80%, aggregate 15% and high alumina cement 5%. It may work even without the cement as the heat will bake the clay anyway. I reckon you could build the whole thing with rammed earth and perhaps incorporate Leca in an insulating layer over the whole thing.
If you build it, I'll promote it on my website Wood-fired Ovens : Welcome

good luck and contact me if you want to meet up info@wood-firedoven.co.uk

[jpmort]

Well, I gave up in a way. I had problems sourcing clay where I live, and realised that this year at least I did not have the time to make an oven. Under different circumstances I would have made my own, and I still want to do that one day.

I went out and bought a bespoke oven that arrived and I put in the back garden. The big problem for me with ready made ovens and also with many opens people make is that I only need an oven to make 2 - 6 pizzas in one session. Using bricks is fine if you need the retained heat for many pizzas and consistency over time. Also this material needs significant warm up time.

So, I went for a rapid heat up oven that uses modern materials and does not used the retained heat principle. Therefore I get an oven that can be up to heat in 50 minutes, and uses the minimum amount of wood. Heat is retained in the fire, and it cools down quite rapidly after cooking. The oven is only designed for pizzas and I also do coffee beans in it.

So thats where I am now, and I am very happy with the results.

I had a look at your website and it was very interesting. I might purchase some products from you in the future.

John

[david s]

If you intend to make the clay permanent by firing you need to get it over. 573 C This is called quartz inversion and renders the clay permanent, ie it will not return to mud when wet. Vitrification is an entirely different process which renders the clay body non porous and usually takes place well over1200 C, depending on what fluxes are present. You might get your oven a tad over 500 C but 573 is doubtful although I'm sure some of the surface clay would reach this temp. All kinds of things happen at around these temps and potters always take this stage slow and controlled, something that is almost impossible in a WFO. I don't think it is worth the effort. You are more likely to create sets cracks in the structure.

[david s]

Sorry set cracks should read stress cracks.