Oven: basalt * Insulation: pumice

[v12spirit]

Hi guys,

Basalt is cooled lava. Where can one find a hotter kiln to bake man made bricks?
Pumice is fairly light and is full of holes that can trap the air. These are the characteristics of an insulator.
What I see above is typical oven-building-materials, don't you guys think?

[stonecutter]

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.

[Wiley]

Re: Oven: basalt * Insulation: pumice

Stonecutter,
When I built my WFO I had some left over 1 part calcium aluminate cement to 5 parts crushed 1/4 minus basalt that I mixed and formed in one of those molds one uses to cast stepping stones. The mold I used created something very close to the size of half a red house brick.

That was about six years ago and that cast extra leftover "brick" has been abused by fire (I have it in the bottom of an outside fire pit...although it is actually a wheel rim) and weather (left out thru snow and rain etc.) The "brick" has held up very well with little apparent degradation.

I would have no problem using that mix as homemade castable for a WFO. As for mortaring solid pieces of basalt together to form an oven I have no personal experience to share but as crushed aggregate held together by calcium aluminate cement it has proven it's stability and durability to me. And as the heat reservoir in my WFO it has worked without problem for six years.

Hope this helps,
Wiley

[v12spirit]

Re: Oven: basalt * Insulation: pumice

Hi Wiley,
It has been a while. Interested to see your fire pit and those homemade basalt bricks if you care.

[stonecutter]

Re: Oven: basalt * Insulation: pumice

Stonecutter,
When I built my WFO I had some left over 1 part calcium aluminate cement to 5 parts crushed 1/4 minus basalt that I mixed and formed in one of those molds one uses to cast stepping stones. The mold I used created something very close to the size of half a red house brick.

That was about six years ago and that cast extra leftover "brick" has been abused by fire (I have it in the bottom of an outside fire pit...although it is actually a wheel rim) and weather (left out thru snow and rain etc.) The "brick" has held up very well with little apparent degradation.

I would have no problem using that mix as homemade castable for a WFO. As for mortaring solid pieces of basalt together to form an oven I have no personal experience to share but as crushed aggregate held together by calcium aluminate cement it has proven it's stability and durability to me. And as the heat reservoir in my WFO it has worked without problem for six years.

Hope this helps,
Wiley

That great, but not what I was talking about.

It's kind of like comparing your basalt aggregate to sand. A large part of which is composed of Quartz. On it's own as a unit or slab, it would not hold up to thermal cycling, yet, it's a usable and lasting component of fire mortar.

[stonecutter]

Re: Oven: basalt * Insulation: pumice

Further, a floor on a firepit is not subjected to the same extreme temperature swings as an oven chamber. In the case of your bricks, you mixed the graded basalt aggregate with a refractory binder. I would not all it a basalt brick or unit.

I'm not against using alternatives to tried and tested refractory material. You just need to understand alternatives are not on par with refractory products.

[david s]

Re: Oven: basalt * Insulation: pumice

Stonecutter,
When I built my WFO I had some left over 1 part calcium aluminate cement to 5 parts crushed 1/4 minus basalt that I mixed and formed in one of those molds one uses to cast stepping stones. The mold I used created something very close to the size of half a red house brick.

That was about six years ago and that cast extra leftover "brick" has been abused by fire (I have it in the bottom of an outside fire pit...although it is actually a wheel rim) and weather (left out thru snow and rain etc.) The "brick" has held up very well with little apparent degradation.

I would have no problem using that mix as homemade castable for a WFO. As for mortaring solid pieces of basalt together to form an oven I have no personal experience to share but as crushed aggregate held together by calcium aluminate cement it has proven it's stability and durability to me. And as the heat reservoir in my WFO it has worked without problem for six years.

Hope this helps,
Wiley

My refractory supplier tells me it is common for industrial chimneys to be lined with calcium aluminate cement and cracker dust (fine basalt aggregate from dust to around 3mm in size)

[Wiley]

Re: Oven: basalt * Insulation: pumice

OK, so I didn't want to start some sort of fight. Stonecutter obviously doesn't like basalt and seeing as how he uses stone he obviously knows what he is talking about using basalt en masse with chisel and hammer. However, using crushed basalt as the sand and aggregate in a concrete mix is a different story IMHO.

Unlike common sand, which is usually comprised of lots of separate distinct minerals, crushed basalt is quite homogenous. Basalt is amorphous, meaning it is uniform in composition. Crushing it simply makes smaller particles of the same material, each with the same physical characteristics as the other. There is only two materials to present problems: the differential of expansion of the calcium aluminate and that of the basalt. So far empirical data would suggest they are very close as the half brick is very much as it was six years ago in spite of neglect and abuse from fire and the elements.

I have taken a couple of photos of some left over quarter minus in a pile. I have also taken a small rectangular trowel and tamped down a small area so one can see how closely it compacts. The space between the pieces would be filled with calcium aluminate cement if one were making concrete of this material.

A basic simple formula for home mixed concrete is one part cement, two parts sand and three parts larger aggregate (stones). This mix is commonly called a 1-2-3 mix. It's easy to remember and it is the reason I decided to use one part calcium aluminate cement to five parts quarter minus crushed basalt. When one says quarter minus one means anything larger than 1/4 inch will be screened out while everything small passes thru the screen and into the quarter minus pile. The range from the largest pieces to the stone dust I accepted as the sand and stones (the 2 parts sand + 3 parts gravel making 5 parts) in a 1-2-3 mix. No special reason it looked right and looked like it would work.

It does. It is easy to work and shape into complex shapes. The very fast cure time is both a blessing and a curse. One it allows one to work progressively almost continuously BUT one has to work fast and mixing small enough batches that one has it placed or shaped before it goes off. Using cold water and six quart batches (one quart calcium aluminate and five of the quarter minus just as if came from the pile) made for some fast moving. No breaks for coffee or whatever while working a batch.

Now would I suggest using it? Well I'm most pleased with my WFO and I know of several others built closely on my design. Two in commercial use. My WFO is steel lined with the basalt /calcium aluminate cement refractory as my heat reservoir. I don't have a need at the moment for another WFO and if I did I would build it very close on the design of my first.

v12spirit: check out the thread on firepits I posted pictures of it there years ago. The pit is portable and has been moved several times. Like lots of what I prefer to build it is made of re-purposed materials. Presently it is on the shores of Lake Jeannette (which is what we call our pond).

Bests,
Wiley

[stonecutter]

Re: Oven: basalt * Insulation: pumice

Uh...I typed a reply and it has vanished.


Anyway the short of it is that I'm not disagreeing with using crushed basalt as a gauged aggregate, just as an oven building unit. I'm not sure that was the intent anyway. And I never said I don't like basalt..it makes a fine wall, and even though it's very hard to shape, it makes beautiful sculptures and polishes like glass.

Also, there are several different kinds of basalt. Some possess refractory minerals like silica and alumina, others contain stuff like sodium and iron. So it would be beneficial to know what you are using, because all natural stone within a specific group, has lots of variance in composition and mineral make up. As an aside, what source says basalt is amorphous? I've never heard that reference to any rock other than gemstone.

I don't disagree with using it as thermal mass over a steel shell either. You can use almost anything that doesn't degrade or burn....even quartz sand. There is a lot of material used as aggregate or even a pozzolins, that could not hold up to thermal cycling on their own as a unit.

I'm interested in mix design and I'm developing a couple right now. I was wondering..... Are the commercial ovens using the basalt mix as a castable or only as thermal mass? How old are they and what is the condition?


Edit: I just skimmed through your build. That is a very cool oven!

[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

[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.

[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.

[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

[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.

[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?