High Temperature Stone/Rock

[rush]

New to the forum, a mason for forty years. Without taking all the time to search threads and links, I was hoping to find some info on the different types of stone could be considered High Temperature stone? I'm a bit familiar with Lava rock, Soapstone..........Considering no moisture is present at the time of firing . Which stones are best. Thanks, Rush

[mitchc]

Re: High Temperature Stone/Rock

Rush, I am also new around here, and in the early planning stages of my oven. I am just beginnning to source materials and build an outdoor fire pit on my patio before moving on to the BBQ island and oven. I recently subscribed to another DIY forum where one of the members told me that granite boulders, which I was planning to build my perimiter with, were the worst stones one could select when it came to reacting to flame and heat. Can you confirm this for me? Having remodled my kitchen a dozen years ago, my wife wanted to install the ever popular granite countertops, which had the selling point of being able to set hot items directly on them...

I find this currious, did you find out anything that supports this rejection of using granite boulders?

Good luck,
Mitch

[james]

Re: High Temperature Stone/Rock

Hi guys, I moved this to the Newbie section -- I think you will get more input there.
Welcome board!
James

[Sananguero]

Re: High Temperature Stone/Rock

Hi I was curious about the same thing... it seems as I have seen more and more old ovens, Ive noticed that many seem to have stone for the hearths, for ex the 13th century communal oven picture from France in Bread Builders. I dont have any first hand knowledge but it seems like no one else responded so I will throw in what I have heard and hopefully bump up this thread to get it started. In Hawaii we have Imu's, pit ovens that are fired with river rocks and volcanic rock the danger is that these rocks may have moisture built up inside and can literally explode! The Hawaiians simply get rid of those ones that do and use the ones that dont. I would imagine there is a safer way of drying these rocks at low temperatures to sort of cure them first. Ive also heard of a guy building rock ovens here with Adze, what the Hawaiians used to make their stone axes with, and is from an andesitic lava flow. It is said to be the hardest rock on the islands. I started to become curious if stone would work, as firebricks are very hard to come by here, and Home Depot wants like 6-7$ a pc plus tax to ship them in. However I just purchased 115 firebricks yesterday that were second hand from an old sugarcane mill. They must be over 50 yrs old and need some cleaning, and as well as have been exposed to moisture. Is this a problem? Can I dry them out at a low temp or should I not worry that the bricks will explode? oh well I guess Ill find out cuz Im buildin an oven!

Karl

[jammyweb]

Re: High Temperature Stone/Rock

I believe that bricks exposed to moisture is not a problem. Lots of people soak their bricks before cutting them to reduce the dust.

Once the dome is built, you have to build a series of gradually increasing fires, this slowly dries out the moisture. As long as you don't try to build a massive first fire, aiming for 400C+ for pizzas - you should be fine.

James

[dmun]

Re: High Temperature Stone/Rock

115 firebricks yesterday that were second hand from an old sugarcane mill. They must be over 50 yrs old and need some cleaning, and as well as have been exposed to moisture. Is this a problem?

Old firebricks are not a problem. You'll drive out the moisture in your curing fires, and you want them wet when you mortar them up, anyway.

I was hoping to find some info on the different types of stone could be considered High Temperature stone? I'm a bit familiar with Lava rock, Soapstone.

Soapstone is the only stone I've heard used for the cooking floor of ovens. We've been warned off granite because its tendency to pop when heated, but I don't know about other stones.

We've heard about volcanic pumice or tufa used as an insulator: The harder types of lava rock are not much used for construction. I assume you're talking about something like basalt, or other igneous stones.

[RTflorida]

Re: High Temperature Stone/Rock

Mitch, granite is a no no for direct high heat flames, whether in a WFO or your kitchen. The granite guys actually offer a torch finish as opposed to the gloss we are all familiar with. Taking a torch to the surface will actually cause small particles of granite to "pop" off, giving you a textured look. Normal heat transfer from a 500 degree pot should not be much of a problem in your kitchen. I was told that the more "figured" granites could have a greater tendancy to crack under high heat.....my experience tells me all is fine. We installed 3 cm granite countertops about 4 yrs ago with a highly "figured" granite. Not a day goes by that I don't set a hot pot or pan on it, with no ill effects to this point.
As the granite yard told me - most of the highly figured granites usually come in the 3 cm thickness because that beautiful pattern or figuring comes at a cost of strength. the tighter patterned of figured granite usually is sold in 2 cm slabs because they are naturally stronger. I say go for it in the kitchen, for an oven - keep the granite outside of the oven as a prep area or landing for pizza removals.

RT

[Sananguero]

Re: High Temperature Stone/Rock

Thanks for the input guys this is a really interesting topic for me since it has the potential to save money and/or help those out who can not source firebrick. I am curious about alternative types of hearth materials that would work for an oven. For example could I simply stack or cut unglazed quarry tiles for the hearth? I was thinking about experimenting with this anyway, kind of like a pizza stone in an oven, but to cover the top of the edges on these old and chipped firebricks if I must use them for the hearth. Some have moss growing out of them! lol

Also has anyone used just straight clay and fired it for the whole oven? Ive read about people doing this in the southwest, even making their own bricks by sundrying them first. How do you tell which clay will be suitable to work with? Here land is geologically very young, but Kauai is loaded with old clay deposits, and Ive heard of a pottery guy firing his own clay there.