Introduction and possibly a unique problem,

[craigs]

if in fact there are any new problems...

I live in Hawaii on the side of a volcano (Hualali to be specific). Obviously the soil is volcanic rocks with little or no soil. I have found the foundation of a "Portugese" oven in the back yard, which appears to have been made of local lava rocks. I am thinking of reconstructing the oven and turning it into a useful appliance and a backyard feature, but have no knowledge of round, stone oven construction. (Other than what I have been able to glean here, of course.) I will be going to the mainland for a few months during which I will plan the project and then try to complete it next winter when I return. Some specific questions:

1. the oven appears to have been constructed directly on the ground, without a stand. Other than ease of use, need there be a stand?

2. I'd like, so far as is practical, to use the materials lying around, i.e. lava rock. I realize that the construction will be more difficult using irregular shapes rather than bricks, and the floor at least will need to be brick, but the esthetic result will be much better, IMHO.

Any thoughts will be well appreciated. I can send a pic of the existing foundation, if anyone is interested. I'm looking forward to sharing this experience with anyone who might be interested.

[Marcel]

Originally Posted by craigs

if in fact there are any new problems...

I live in Hawaii on the side of a volcano (Hualali to be specific). Obviously the soil is volcanic rocks with little or no soil. I have found the foundation of a "Portugese" oven in the back yard, which appears to have been made of local lava rocks. I am thinking of reconstructing the oven and turning it into a useful appliance and a backyard feature, but have no knowledge of round, stone oven construction. (Other than what I have been able to glean here, of course.) I will be going to the mainland for a few months during which I will plan the project and then try to complete it next winter when I return. Some specific questions:

1. the oven appears to have been constructed directly on the ground, without a stand. Other than ease of use, need there be a stand?

(M) I would say no. But do you really want to bend over to tend your fire and bake your pizza?

2. I'd like, so far as is practical, to use the materials lying around, i.e. lava rock. I realize that the construction will be more difficult using irregular shapes rather than bricks, and the floor at least will need to be brick, but the esthetic result will be much better, IMHO.

(M) If you are trying to faithfully reconstruct the old Portuguese oven then it seems to me that you would have an oven that doesn't hold the heat very well as (some) volcanic rock can be quite porous. You'd then have a restoration which would be special but probably not very good for baking.

(M) If you want to have your cake and eat it too then consider the traditional refractory brick material and use the volcanic rock (if the porous type) for a decorative shell - housing. In that case, be prepared for lots of rain water soaking into the housing and needing to be driven off before you could bake. Some of that may be partially offsetable by placing a layer of aluminum foil between the refractory brick and the porous volcanic. But I think the wet housing would still hold you back in terms of heating time.

Any thoughts will be well appreciated. I can send a pic of the existing foundation, if anyone is interested. I'm looking forward to sharing this experience with anyone who might be interested.

(M) Aloha!

Marcel

[james]

I would agree with Marcel. Volcanic rock has lots of little air holes in it, which makes is great insulator, but not a good material for the oven floor or dome. Those are more dense and hold, rather than stop, heat.

As an aside, ovens in Naples use the tufo (volcanic rock) for insulation, and vermiculite is basically volcanic popcorn. Both good insulators.

For the stand, you can put an oven hearth directly on the ground, but it would be pretty hard to use. You would end up stooping over all the time to use the oven. It isn't too difficult bringing the hearth up to cooking height and worth the effort.

Enjoy the sun!
James