Which Clay?

[shvuntz]

In want to build an oven starting with a sand dome then clay rolled into balls to make the dome

This looks good to me.
then I will put another 5cm of clay after that...
fireclay grouting and bricks for the outside of the dome after that as protection against rain.
leave the sand core in, and let the clay dry for 3-4 weeks at least
then dry with a heater?..so it doesnt crack..
this is something i read, does it sound ok? helppppppppp
And what clay do I use, is it a tandoori clay I need?

[dmun]

I haven't been near a pottery studio in thirty years, but I do know that that much potters clay is going to cost you an arm and a leg. Anything that thick is almost guaranteed to crack(think dried out riverbed), but not to worry, since it won't vitrify at oven temperatures, you can always smear some wet clay back in the cracks.

Why clay, again?

Also, the entry of that oven is very long compared to the diameter of the dome. Have you actually seen/cooked in the oven you illustrated? What's the source of the photo?

[shvuntz]

ahhhh,
its a pdf file i got from a guy on ebay who has built it and sells his formula for about 7 pounds,,,hes a german guy, which makes me think he prob knew what he was doing..ahhh. back to the drawing board.
i was trying to save myself 1,200 pounds which is what is being charged for the dome bit..
i guess i will have to cough up,,

[Inishta]

shvuntz...........I've got to admit to being a tad confused. We have gone from a Danish rock oven from e-bay to a Forno Bravo oven to a set of German oven plans at £7 on e-bay again. I think of the 3 options the latest is the least practical. The technical issues involved seem quite daunting.

[edschmidt]

It may be a dead issue, but Ill weigh in anyway. Leaving the sand core in for the 2 weeks would be utterly disasterous. Clay shrinks in the 20% range as it dries. So the dome would be shrinking, the sand would be stationary, and the cracks would be huge. If you were going to do it I would reccomend fireclay mixed 50/50 with grog, or crushed firebrick (far less shrinkage). I would remove the sand as soon as I felt reasonably sure that the clay could hold its own weight. Then Personally I would attempt to vetrify at least the inner chamber of the dome using a leaf blower, bellows, accetalene tank, etc. Then I would finish the exterior by building layering wood, covered with metal pans, and the entire exterior covered in dried cow chips. Light, and vouila.

What was I talking about?

[shvuntz]

HA HA,,,it's now 7.30am here in the uk, it's a Bank Holiday, everyone is asleep 'cos they don't have to be anywhere, but i'm up on this forum, because I have become obsessed ...
Yeah I have thought about different options, I guess I am troubled with the ideas that I would have liked to have built it from scratch but I don't think it's going to happen..and I have thought about many ways to go round this but goodness knows where we will end up.
What I do know is that I want something very permanent, so clay isn'y an option,building a brick dome?..erm maybe..Watch this space..or feel free to contribute to my dilemma....

[Xabia Jim]

Have you downloaded the free plans from FB yet?

Search around for recycled material, surplus bricks, etc. Maybe you can find an old chimney they've torn down....might help you save some money. There are home recipes for the refractory masonry on this site. There are also some discussions of functional budget ovens.

I think if you're willing to do the legwork and lots of the labor, you can keep costs down. But if you want a permanent oven, invest in it, it will pay you back!

I look forward to seeing you cook!

[Carl]

Hi Schvuntz,

Sounds like you're taking the same road I took. Shocked at the price of firebrick in the UK, I used a fireclay & grog mix instead over a sand form, then dried it out with a halogen heater. I'm still finishing it off, but am getting ever closer to firing the thing, so expect more posts... My oven's been very cheap (thanks to lots of recycling, freecycle and ebay), so it can be done!

I've got a lot of the details on this thread: My oven build posts (Another UK oven started)

There's a lot more detail on my blog - see the link at the bottom of this message.

Couple of UK-centric tips that might be of use: the cheapest clay I could buy was fireclay (handy), try builders merchants as it's more expensive from pottery suppliers. The cheapest vermiculite I could find was from Travis Perkins, at £7 per 100 litre sack.

Carl

[shvuntz]

AGHH thanks Carl...Today we dug out the base...and in a min we are pouring in the cement ..