Oven: basalt * Insulation: pumice

[stonecutter]

Re: Oven: basalt * Insulation: pumice

Any stone is not really suitable for a high temp oven. Any monolithic structure is going to crack, but one made of a natural stone will also flake and spall.

Ah, but with one exception, soapstone. Though if there is heavy veining, it will likely crack.

[Tscarborough]

Re: Oven: basalt * Insulation: pumice

Any stone is not really suitable for a high temp oven. Any monolithic structure is going to crack, but one made of a natural stone will also flake and spall. On the other hand, using natural stone as an aggregate is pretty much a necessity. So long as it has thermal characteristics similar to the matrix material it should not be an issue.

Obviously in the past, and even today, an oven can be built with sub optimal materials and they will work. How long and how well will only be determined empirically. I would never consider using less than the best I can afford in my current situation, but in the past I have certainly done so. The best rule is: Build to your budget and the value of your time.

[Wiley]

Re: Oven: basalt * Insulation: pumice

Just as an aside, here is a photo of 13 tons of quarter minus basalt I had delivered today. It looks like a larger grain size because when it is wet it had a natural tendency to clump together. While this is a warm spring day the stuff came from a large pile wherein it was wet inside. This is the Pacific Northwest where water is plentiful and rain common.

I am using the quarter minus as underlayment for foundation and leveling beneath red bricks (pavers) for a patio around the WFO (which I'm finally getting around to building). It packs tightly and makes IMHO a better foundation than straight sand. Any left over will be used on the parking area.

Bests,
Wiley

[v12spirit]

Re: Oven: basalt * Insulation: pumice

Yes that is why I thought of those materials. I find them in my garden, in the farm, on the way.. They just need one to pick them up and collect them. I will be seeing how I can start collecting them.

[stonecutter]

Re: Oven: basalt * Insulation: pumice

Thanks stonecutter for the details,
I hope there is a heuristic way one can find out the components of the stone (iron, magnesium,..) like color, structure, or even geographic classifications. I live in southern Syria where basalt is plentiful and free.
BTW: Regarding pumice, provided this is a right descending order of insulators (Calsil board or IFB, Vermiculite, Perlite). Feels like pumice comes right after Perlite, or does it?

You have access to plentiful and free basalt? I think those are a couple of great reasons to build an oven IMO. Who cares if it lasts? Like I said, maybe the mineral content of your basalt will lend itself to successful firings.

I can't say where pumice ranks against other kinds of insulation, I haven't tested it or even used it. It is more dense than perlite or vermiculite, so I would guess that pumice would not have as great of r-value. Again, if you get it free or cheap, why not try it.

I always advocate using the best possible material or employ the best possible techniques, but try not to be so rigid as to discount alternatives to either. The only time I do is when you are building an oven for a commercial venture or for a client.

[v12spirit]

Re: Oven: basalt * Insulation: pumice

Thanks stonecutter for the details,
I hope there is a heuristic way one can find out the components of the stone (iron, magnesium,..) like color, structure, or even geographic classifications. I live in southern Syria where basalt is plentiful and free.
BTW: Regarding pumice, provided this is a right descending order of insulators (Calsil board or IFB, Vermiculite, Perlite). Feels like pumice comes right after Perlite, or does it?

[stonecutter]

Re: Oven: basalt * Insulation: pumice

I have always thought of basalt as one of the toughest stones and didn't even thought of any crackings under thermal cycling!!
Besides. There are many houses in my region that are built entirely from basalt. When one enters one of those houses, one can hardly believe that they are NOT air conditioned. They're warm in winter and cool in summer. That put me under the impression that basalt was not a conductive!!
Looks like there are some facts about basalt that are not as I once thought they were.

It is tough, I wasn't kidding about broken chisels and wearing out diamond blades. I assumed in the original post that basalt units( not cast refractory brick with basalt aggregate) was being considered to build an oven. Also, there may be some basalt out there that could hold up to thermal cycling in an oven, mainly the ones that contain high silicate or magnesium levels. Most of the basalts I have experience with are high in iron, and I've seen them break up from heat when they where used to line a simple firepit.

As far as your observations of stone houses, that's a different application of stone than a small, thin shelled masonry structure like wood ovens. Being mass based, the stone isn't experiencing the same stresses that it would get in an oven. Since the heat is being distributed through a larger area, I feel that changes the way stone responds to thermal cycling...and allows you to use stone that would break apart in a thinner shelled build. An example of this is the massive limestone oven in Tractormans thread.

[stonecutter]

Re: Oven: basalt * Insulation: pumice

Stonecutter,
Is it just cracking under thermal cycling that makes using limestone or basalt as an aggregate work fine, while using them as a building material doesn't?

I think it does, but it also depends on what the stone is composed of. Generally though, I feel the main reason you don't see most stone used like firebrick, is because of all the faults inherent in stone. Like I said, all basalt isn't the same..there may be some out there that would hold up great if you used it as an oven building unit....namely, ones with a higher magnesium or silicate content.

[v12spirit]

Re: Oven: basalt * Insulation: pumice

Basalt is an igneous rock, but that doesn't automatically qualify it as a suitable oven material. Basalt would make a poor oven. Besides being highly conductive, it won't hold up well to thermal cycling....you'll get cracking. Besides that, have fun shaping it. You'll be hard pressed to find a stone that breaks more chisels or wears out diamond blades faster than basalt.

As far as using pumice goes, it works as an insulator sure. But there are better ones like perlite or expanded clay that are easy to find, as cheap, and work better.

Unless you have nothing else to work with, then don't bother with these materials to build an oven if you care about quality and efficiency.

I have always thought of basalt as one of the toughest stones and didn't even thought of any crackings under thermal cycling!!
Besides. There are many houses in my region that are built entirely from basalt. When one enters one of those houses, one can hardly believe that they are NOT air conditioned. They're warm in winter and cool in summer. That put me under the impression that basalt was not a conductive!!
Looks like there are some facts about basalt that are not as I once thought they were.

[v12spirit]

Re: Oven: basalt * Insulation: pumice

Interesting link. But questioning the use of basalt in aggregate form wasn't being contested. Using it as an oven building unit was. Notice that next to basalt they have granite for the 800c threshold. Try building an oven out of granite. That was the point, lol. Same goes for limestone listed as an aggregate on the table on the TRS sheet.

As noted, I'm not even sure that using basalt as building units was the intent.

Stonecutter,
Is it just cracking under thermal cycling that makes using limestone or basalt as an aggregate work fine, while using them as a building material doesn't?

[shuboyje]

Re: Oven: basalt * Insulation: pumice

Interesting link. But questioning the use of basalt in aggregate form wasn't being contested. Using it as an oven building unit was. Notice that next to basalt they have granite for the 800c threshold. Try building an oven out of granite. That was the point, lol. Same goes for limestone listed as an aggregate on the table on the TRS sheet.

As noted, I'm not even sure that using basalt as building units was the intent.

Should have been more clear that my post was with regard to Wiley's cast bricks.

[cobblerdave]

Re: Oven: basalt * Insulation: pumice

G'day
Seems very timely that the forno newsletter contains the new forno bravo venture. Bella outdoor living. A range of outdoor kitchens grills and WFO .
The Bella pizza ovens have a shell of 304 stainless steel. I'm presuming a mass layer then ceramic insulation with a firebrick hearth. Heat up time 15 to 20 mins to pizza temps.
Seems we have taken the next step in the evolution . First the big mass bread bakers then to the insulated weekenders now it looks like we have arrived at the instant oven .
That 15 min heat up is going to be the big seller. Less mass less baking I bet.
Regards dave

[stonecutter]

Re: Oven: basalt * Insulation: pumice

I think it is safe to say Basalt is a suitable refractory aggregate, unless of course they are purposely misguiding consumers so their castings fail and they have to buy more Ciment Fondue, lol.

Interesting link. But questioning the use of basalt in aggregate form wasn't being contested. Using it as an oven building unit was. Notice that next to basalt they have granite for the 800c threshold. Try building an oven out of granite. That was the point, lol. Same goes for limestone listed as an aggregate on the table on the TRS sheet.

As noted, I'm not even sure that using basalt as building units was the intent.

[shuboyje]

Re: Oven: basalt * Insulation: pumice

Sorry I was too busy to post this earlier in the conversation:

CIMENT FONDU?

I think it is safe to say Basalt is a suitable refractory aggregate, unless of course they are purposely misguiding consumers so their castings fail and they have to buy more Ciment Fondue, lol.

[Wiley]

Re: Oven: basalt * Insulation: pumice

Stonecutter, thanks for the kind words on my WFO build. My WFO has worked well and without issue for the six years. I am very pleased with the rapid heat up time...I find it amazing some people have to fire their ovens for two hours before reaching pizza temps.

In quick answer to the other ovens I referenced. They were built using a steel liner as I did with my WFO. One had a thread here and became "Dented Bouy". They do a brisk business and have successful Saturday market presence in several of the communities near where I live. The builder was successful enough that he was going to build a second WFO and "branch out" but elected to build a WFO on the same design for Finnriver Farms. Here's a link with photos of both WFOs: http://www.dentedbuoy.com/

There were others but they contacted me thru PM and I'm not sure they wish to have me broadcasting their names etc. For whatever reason they did not wish to start a thread. I actually added a few missives from my pm box but that seemed too egotistical and just because someone said they were building didn't mean they did or that the WFO performed as expected. But the question was about how their age and condition. The only two WFOs that I can claim to have real knowledge about age, condition and how well they work besides mine are the two built by Dented Bouy and he used very similar designs to mine. Those WFOs are working well and are used commercially on a regular basis.

I was too broad in inferring that all basalts are amorphous as certainly many cooled slow enough for individual minerals to come out of solution and form individual crystals. The stuff available around here is quite uniform in texture and grain size. I have seen a spear point that was found on a local beach which appears to have been knapped of the local basalt.

There are several quarries in the general area where I live. The basalt here was/is quarried as it is both near the water and very strong material. The quarry that supplied much of the rock used in Puget Sound has closed (Mats Mats). It basically ran out of extractable rock. They were well below sea level and only a short distance from their blasted out basin where they loaded the barges. It was transported significant distances by barge to be used in breakwaters because it met the classification as Class A rip rap. There is much local debate as another quarry (where I got my basalt) wishes to run a long distance (several mile) conveyor belt system to a new shore side location. One major issue in this case is liability for damage from barges to the Hood Canal Bridge (a floating bridge) in the event of collision as well as noise pollution, but I digress.

Regarding using other materials: over the time I have been on the forum there have been several WFOs of different designs proposed or for that have brought to the forums attention. If memory serves there was at least one that consisted of two steel skins with the interstitial space filled with some sort of sand used to act as a refractory.

One of the many reasons I selected basalt was because of it's available locally and inexpensive. I would really suggest that people look into what is available in their local area before purchasing anything that is brought in. The whole "Think Local" idea. Along those same lines Dented Bouy Wood Fired Pizza and Finnriver both use local made cheeses and their flour is made with 25% (if memory serves it might be more now) locally grown wheat. I find it amazing that people spend lots of money importing some particular cheese or wheat from some far off land before exploring what is available locally. The reason the pizza in Italy tastes the way it does is due to the fact they are using locally sourced (Italian) materials. It seems to me one could have every bit as much chance of producing excellent pizza made with local ingredients. Pizza with a local flavor. Who knows maybe someone will start exporting your local ingredients because they want to duplicate the way it tastes just like many are trying to do by importing Italian ingredients. I'll get off my soapbox now.

Anyway, it seems if one can make a successful WFO out of cob one can make one out of a very very large range of materials. It simply take the ability to think outside the box and be a bit creative.

Bests,
Wiley