Volcanic rock

[Nick House]

I am planning to try and build an oven in Indonesia, we have masses of volcanic rock everywhere. Could I use this instead of the fire bricks?

Any help or advice or ideas would be greatly appreciated!

[Johnny the oven man]

Re: Volcanic rock

Is it the porous type of volcanic rock? I think that type would be more insulative.

[Neil2]

Re: Volcanic rock

What is the density ? How much does it weigh per cubic foot ?

[Nick House]

Re: Volcanic rock

Gents

We have all sorts of volcanic rock from a hard granite type to a more soft pumice type. I would have to write to a friend and get them to sort out how dense either or both are. As I live in Saudi it might take a while. Our property is quite remote and so I was thinking that using locally available materials would be preferable especially seeing as I am not sure I could get fire bricks and even if I could I am sure they would be very expensive.

Do you guys think that it would possible to build an oven using these type of rocks?

Thanks for any advice you have, I am a complete novice at this type of thing, and just trying to get some information.

[Tscarborough]

Re: Volcanic rock

As a rule natural stone of any type is not a good choice for the direct fire portion of your oven. Low fired adobes or common solid brick would be a better choice. They may not last as long as firebrick, but they will suffice and both are cheap and available everywhere.

[Nick House]

Re: Volcanic rock

Thanks for the info. I will bear all these things in mind. I am tempted to experiment a bit before I finally decide what to do. Why is generally a bad idea to use natural rock?

[dmun]

Re: Volcanic rock

Hard stones (We're exposed to granite in the states) have a reputation for cracking and spalling (surface chipping) when exposed to direct flame. That said, so do common bricks, so there might be no real reason not to try them, if there's a reasonable way to cut a hard volcanic stone like basalt.

[Lburou]

Re: Volcanic rock

Volcanic rock runs the gamut in specific gravity, from heavy basalts to light pumice. The stone resultant from a light and frothy expulsion from a volcanic eruption has more trapped air (read more insulative capacity) that might insulate better than a more dense rock. Either way, the rock will be strong but brittle.

You can build the oven from volcanic rocks, but will likely not have much stored heat energy or insulative affect. But, practicality is king in the remote areas you describe too. You may find some local wisdom in the villages for outdoor cooking....Hopefully a small price to pay for living in paradise

Decomposed volcanic soils become clay eventually. Clay may be available depending on the age of the eruptive materials, you could use that some way I'm sure.

Good Luck

[Nick House]

Re: Volcanic rock

Thank you, I am slowly understanding more and more of the posts. And understanding the importance information in something like this. But in the end I am sure that a bit of practical experimentation is what is really required. What would be the best way to experiment?

[dmun]

Re: Volcanic rock

I think lburou's suggestion of tapping into local knowledge is a good one. What stone or material is locally used for fireplaces or cooking?

As far as actually using volcanic rock, I would ask, how is it used locally? Is it available in blocks or sheets?

[azpizzanut]

Re: Volcanic rock

Hello Nick House,

Volcanic rock can be used in the base construction and outside covering of an oven.

The biggest hurdle is to determine which volcanic rock can be used to hold heat and make a hearth then finding a method to cut that rock to workable size. You want the hearth as flat as possible and with tight joints. Lightweight cinders or pumice can be used for insulation, as already mentioned. You need dense rock inside the oven to hold heat and layers of light rock on the exterior to insulate.

My research of island ovens provided a few photos and descriptions of examples made by Portuguese settlers in Hawaii. The hearth appeared to be made of brick. Portuguese Stone Oven Baking | Kona Historical Society Most "ovens" made by native peoples were of the pit variety where stones are heated by fire in an earthen hole then native foods placed on wet vegetable matter, then covered with more leaves and then earth from the hole. The food cooked by steam. Settlers from Europe constructed ovens like those made in their homeland and which we are more familiar with for baking bread. Settlers could otherwise use pit ovens or an open fire for roasting. It would have been easy to bring enough brick by ship for a hearth (as ballast) then use native materials for the base and exterior.

You might find a local source for clay and make a cob oven with cinder insulation and basalt exterior. If you intend to make the oven from cut lava rock then you should find a source for refractory mortar materials and cement. A demolished brick building might provide enough solid red brick to make a hearth. However, a Google search revealed a number of stone suppliers and refractory brick producers in Indonesia.

I'd suggest learning as much as possible about wood fired bread oven construction to get an idea of the basic requirements and fabrication methods then adapt your local materials to it. A good source of information is the free Pompeii oven plans and the various Forno Bravo pre-cast ovens.

Best of luck,

Bob

[Nick House]

Re: Volcanic rock

Mainly people don't use fire to cook with in fireplaces. So the local rock is not really used that much, not even in building, most people use wood. I agree that using local knowledge is the best way forward, I will do some research as soon as I get home. I have downloaded the plans and have seriously started to read them. I also looked online for brick suppliers and there are many, but as our property is not near any of those places it would be very hard to get them delivered. I do know that we can get clay easily, by digging it up from a friends garden so that could be a very good way of doing this. And we will keep an eye out for some old buildings to nab the bricks from. Thanks for your valuable advice, I will continue to read up and research as much as possible, before we get home and start to build. Thanks again.

[Lburou]

Re: Volcanic rock

...snip... I do know that we can get clay easily, by digging it up from a friends garden so that could be a very good way of doing this. And we will keep an eye out for some old buildings to nab the bricks from. Thanks for your valuable advice, I will continue to read up and research as much as possible, before we get home and start to build. Thanks again.

The more information you gather, the better decisions you can make when the time comes.

When you are looking for clay, look for a light colored clay, one about the color of desert combat boots -could even be a shade lighter. Alumina is about that color and alumina is one of the more important components for making fireclay and fire bricks (and, fornobrabo 'home brew' mortar).

[Nick House]

Re: Volcanic rock

Thanks I will keep that in mind. I am trying really hard to get all sorts of info from as many people as possible so that when the time comes, hopefully in the summer, I am a firm believer in starting to research nice and early, I will be in the best possible situation. Wow that was a really long and convoluted sentence, sorry. I will try and find the light coloured clay I am fairly sure it is a bit darker than what you describe, but I may be mistaken. Thanks, all of this sort of advice is great and I thank you all.

[Lburou]

Re: Volcanic rock

Hello Nick House,
....snip....You might find a local source for clay and make a cob oven with cinder insulation and basalt exterior. If you intend to make the oven from cut lava rock then you should find a source for refractory mortar materials and cement. A demolished brick building might provide enough solid red brick to make a hearth. However, a Google search revealed a number of stone suppliers and refractory brick producers in Indonesia. ....snip....
Bob

The local refractory I visited sold all the rare items we need for a specialized wood fired oven. If you could expand Bob's search for a refractory in Indonesia and ship a few firebricks, ceramic insulation (for the top of the oven), and rigid refractory insulation (for the oven floor) to your locale, you would have the hot portions of your oven. Then, finish it with local materials: The best of both worlds.