[brucea]

We just had a firepit built of concrete blocks covered in Cultured stone and a Bluestone 12" wide top above the cultured stone.We made a few fires and the fires were extinguished using a garden hose. The Bluetone on 1 side cracked all the way across the width and the cultered stone beneath it has a hairline crack going down towards the base. The firepit is lined on the inside with firebrick. The contractor says that the cold water on the hot Bluestone caused this to happen. Does anyone have an idea if this is correct. The Bluestone is 1 1/2 thick.
Thanks all
Bruce@optonline.net

[Greensmith]

If you sprayed that while it was red hot, he is probably correct. The same principal as throwing cold water onto a hot coffee pot. I am having a hard time visualizing this though. Was the bluestone adhered to the firebrick with an over hang into the fire pit?

[brucea]

There is about an 1 1/2 overhang into the firepit. The cultured sone veneer also has a hairline fracture vertically from the bluestone down about 6 inches. I had always assumed that Bluestone was more rugged than it seems to be. I thought that even though it may have gotten hot from the flames --it would not split when cooled quickly. Isn't a flame edge applies to Bluestone with a torch and water at the same time??
Thanks for your response!!
Bruce@optonline.net

[Greensmith]

The flaming technique has been discussed in another thread at length. But I think the crucial difference here is going to be how much surface area got deep heat, as opposed to a quick surface flame.

[Lanelle]

The flaming technique is using water and heat to cause the stone to flake apart in a small, controlled way. Putting water on hot stones can certainly cause cracking.

[Stonehenge]

You can crack an engine block throwing cold water on it while it's hot. You can certainly crack stone doing the same thing.

You can also crack stone by having a fire that's too big for the space. Make it a furnace and the stones and mortar will want to expand more than they can when mortared together, so they crack. Simple physics.

[brucea]

OK--Now I know that you can't extinguish the fire with water---but if you can crack the bluestone with the heat of a fire in a firepit----how will I know how hot is too hot. We certainly do not put more wood in the firespace than the space will hold. We are using a firegrate that is several inches smaller than the space. Is the 1 1/2" overhang of the bluestone the problem? Would you happen to know the specification of the top heat that an 1 1/2 thick piece of Bluestone will withstand without a problem.

Thanks

[brucea]

Ok---More to my problem. We made another fire and the opposite side of the firepit's bluestone also split through the 12 " side just like the piece that is on the other side of the firepit. We did not use any water to extinguish the fire. Do you think that the stone was already fractured on the inside or will this continue to happen if we replace the Bluestone damaged pieces if we simply continue to make fires and let them burn out on their own?
Would another type of stone be better for the top of the firepit? Ever hear about Westchester stone pieces?
Thanks again,
Bruce@optonline.net