Thanks for the feedback! I'm really pleased you like the oven - having never laid a brick before, let alone actually built something, I am kind of pleased with it myself.
John - 'sun-dried organic dung' could sound edible, I reckon; I will tap up some marketing buddies from my past as a suit-wearing sales monkey and see if we can go into production... 'where there's muck, there's brass' as the saying goes. The delivery drivers are a little unreliable though - prone to outbursts of temper and fond of knocking trees over and so on.
Jackie - Thank you! I'd read about using wood shavings mixed with clay slip (yoghurty, runny wet clay soultion) as a middle layer, and also about using cob. This is a kind of halfway house between the two - the dung is dry, then broken up into individual fibres and mixed with the clay slip. The fibres give structural integrity to the layer as you can link each block to the next and the fibres help hold it together. That said, I have read that for an insulating layer the theory is that the woodshavings (or in this case plant fibres/straw) eventually degrade or burn out to leave air spaces whuch form a hoineycomb insualtion layer/heat stop. After 4 hours of not-overly-aggressive firing you can rest your hand on the top of the dome outside and sure, it's hot, but it won't take your fingerprints off. So what is the benefit of using dung? It is free, readily available, and we don't have any woodshavings or straw. There are about 130 elephants here and they drop maybe 100pounds of the stuff every day. The total budget for this build has been 1 bag of cement plus $2.82 for 25 bricks I bought from a building site for the edges of the hearth.
mkevenson - smouldering ele poo does have a strangely pleasant, almost incense-y smell... but the oven mostly smells of drying, damp brickwork at the moment, with maybe a little earth undertone...
Chicago Bob - thank you! Really appreciate it. Yeah, we have a sunken pool here, which after the recent floods (we had three times last years rain fall in 24hrs) was even more sunken but only at one end... our borehole's been underwater for nearly a month so its pumping brown water still. Grrr. But the pool is good - there's a waterhole for wildlife 50yards outside the fence so you can be in the pool and watch the elephants or whatever. Pictures of pizza will follow eventually...
TXCraig1 - Elephant poo tends to smoulder, though of course if you get it hot enough, yeah, it burns. Its not used on any fire-facing surface though and as per my reply to Jackie, the theory is it eventually forms a 'honeycomb' insulating layer, just as with woodchips.
Shuboyje - In a word, no. Believe me, folks coming here can be a little paranoid about all sorts of stuff; there was a cholera outbreak just across the border a few years ago and one of the folks asked me if it was safe to shower. I could give many more examples... the poo isn't on a food-facing surface though. For reasons I can never understand it is considered normal in some lodges to get folks to join in giraffe poo spitting competitions. Faeces is not knowingly going in my mouth under any circumstances, although I am given to understand that thre internet has plenty of sites dedicated to exactly that. So no, I have no probs making an oven using herbivore poo. We collect lion, leopard and cheetah scat for www.greendogsconservation.com
for their predator-detection dogs to be trained with; that stuff is disgustingly stinky and heavily laden with parasites. Elephant poo is kind of innocuous by comparison.
I think that's all...
Thanks for the interest, conversation and discussion, folks, and I am really glad that (it seems) you like our oven!