In New Zealand fuel wood is the best source of heat for cooking. The challenge is to make low cost efficient appliances from local materials.

Our starting point has been to look at finding a good design for both a 'pizza' or earth oven and a rocket stove, and possibly we can combine the two in a way that is practical for the user - the cook

Earth Ovens

We've built enough of these to gain some confidence, however we are aware that there is a lot more to learn. What we can share at present are issues that we have resolved and those that we haven't yet. These include:-

• the best DIY book is Build Your Own Earth Oven: Kiko Denzer and Hannah Field
• dont underestimate the usefullness of a good thick insulation layer around your inner heat mass layer. Cob is not particularly good insulation, better to use a mix of pumice/fibre/loam (as little loam as can still hold together) or if pumice is diificult to get, try pulped paper/fibre/loam. 20% loam renders the result flame proof.
• We have built a good door, made from the same two layered mix of high heat mass inner and insulative outer. We used a wooden handle with no.8 wire woven through the handle and through the insulative mix. So far it works good, the handle stays cool, and it all looks good.
• We've finished our outer layer off with a mix of loam and cow manure. Several layers between drying. We will keep you posted as to how effective this is as a weather proofing in NZ. What have others used??
• Its always a bit of a knack using the right amount of wood to match your cooking requirements (heat intensity and longevity) However if you use too much and have to take some of the embers out before they are burnt right out, douse them in water and once they are dry use them as you would charcoal. (or just add to the fuel mix next time)
• Line up several uses, after the intense heat of cooking pizzas or bread, find another use for the less intense heat, including drying once its cooled down a bit
• So far we have used fire bricks on the base. Has anyone had experience with normal bricks or loam/sand mixes that stand up to the heat. (fire bricks are quite expensive)
• Are the flue exits over the door more effective, or are they just fashionable???
• Watch this space, once we have got a bit of feedback on some of the issues above we will publish a brochure to support those wanting to build there own and giving more feedback on our experiences.

Rocket Stoves

Rocket stoves were invented by Larry Winiarski, particulary targeted at third world conditions where there was a need for low cost, efficiency and use of small firewood. They are remarkable for their simplicity and are being used by many all round the world. We like the original idea, but want to adapt them to our culture where we frequently use more than one pot and have some simmering while other boil. So we're trialling a Rocket stove with a top plate. Its been done before but its all in the detail which isn't conveyed clearly in photos.

For a good introduction to Rocket stoves just google, there's lots to read. We made our base out of a pumice/pulped paper/pine needles/loam mix, trying to keep it as light as possible. In retrospect it is too heavy so we'll find ways to drop some of the bulk next time. The combustion and feeder chambers where formed around tailor made cardboard boxes. Once these were removed the walls of the chambers were plastered with a thin layer of a loam sand plaster. The plate is supported by 4 steel pegs in the base. Our first use of the stove was for cooking flat bread directly on the plate. It certainly got very hot and they were scrumptious. However while there was plenty of hot air coming out the chimney, we had too much smoke come back out the feeder chamber. We'll try some modifications to the gap under the plate and try again.