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newhopeclan 05-14-2014 10:23 AM

limestone vs. brick construction
 
I am planning to build a dry-stack pizza oven in my back yard as a first inexpensive step toward something a little more permanent. This link shows the general level of complexity / design of my oven:

http://www.westernexplorers.us/A_sim..._bake_oven.pdf

I am just starting to research my project, and have a fundamental question. I have access to a pretty decent quantity of modular limestone (similar size as brick) that was originally used as cladding on a home. The actual floor of the oven will be firebrick, but assuming I can get the joints tight, would limestone be an appropriate material for the walls and roof?

I don't see a lot of dry-stack ovens on this blog, so if there is another more appropriate site, feel free to point me in the right direction.

As for actually using the oven, I find some resources that say to remove the embers and all coals/soot before baking, while others leave them in. When is one appropriate vs. the other?


Thanks in advance for your help!

Mike

Toomulla 05-14-2014 02:11 PM

Re: limestone vs. brick construction
 
Looking forward to the responses as I thought you burnt limestone and wood in a kiln to make lime but don't know the temps involved

wotavidone 05-14-2014 04:38 PM

Re: limestone vs. brick construction
 
Quote:

Originally Posted by Toomulla (Post 173649)
Looking forward to the responses as I thought you burnt limestone and wood in a kiln to make lime but don't know the temps involved

You need a minimum of 900 Centigrade to decompose the carbonate. Unlikely (but not impossible) to achieve this in a wood oven. In a dry stacked oven where expense is a concern, I'd certainly be trying it. If it doesn't work nothing much is lost.
I reckon you'd need real bricks for the floor. The coals sit on that, and wherever there is a localised hot-spot you may damage that area if it's just limestone. Marble floors fail, apparently, and marble is recrystallised carbonates.
So floor no, dome maybe, if it's a dry stacked oven where little is lost if it fails. I'm all in favour of experiments that further the knowledge, as long as the loss on failure is low for the experimenter.

Quote:

Originally Posted by newhopeclan (Post 173635)
As for actually using the oven, I find some resources that say to remove the embers and all coals/soot before baking, while others leave them in. When is one appropriate vs. the other?


Thanks in advance for your help!

Mike

One tends to leave the fire in (swept to one side) to maintain high temps when cooking pizzas, and clear it out when baking bread. For roasts, a small fire might help, or might not be necessary, depending on how much thermal mass you have and how much you loaded it with heat.

wotavidone 05-14-2014 04:42 PM

Re: limestone vs. brick construction
 
A postscript - I just read the linked PDF. I would say that oven will probably not acheive temperatures high enough to decompose limestone. I'd certainly give that a try - especially if those limestone blocks are free:D

wotavidone 05-14-2014 04:47 PM

Re: limestone vs. brick construction
 
PPS, that oven is a little too simple. You should at least overlap the bricks in the corners so the side walls are tied to the back wall.
Wouldn't be good if the whole lot fell over while you had the fire going.

Tscarborough 05-14-2014 07:18 PM

Re: limestone vs. brick construction
 
Trust me, limestone will not last long in a fireplace/firepit, much less an oven.

wotavidone 05-14-2014 07:42 PM

Re: limestone vs. brick construction
 
Quote:

Originally Posted by Tscarborough (Post 173669)
Trust me, limestone will not last long in a fireplace/firepit, much less an oven.

Sounds like it ain't such a good idea. Maybe just settle for any fired clay bricks you can get hold of.

Toomulla 05-15-2014 02:44 PM

Re: limestone vs. brick construction
 
Quote:

Originally Posted by Tscarborough (Post 173669)
Trust me, limestone will not last long in a fireplace/firepit, much less an oven.

You could use the lime to mix grog for the replacement brick oven

wotavidone 05-15-2014 03:23 PM

Re: limestone vs. brick construction
 
Quote:

Originally Posted by Tscarborough (Post 173669)
Trust me, limestone will not last long in a fireplace/firepit, much less an oven.

It's all very confusing.

On the one hand, we put lime in the mortar, expecting the lime (calcium hydroxide) will carbonate and turn back into limestone (calcium carbonate), thus providing the strength after the Portland Cement breaks down.

On the other hand, we say don't use limestone (calcium carbonate) for the oven as the heat will break it down.

It's all too hard, think I'll go light the oven and cook something to take my mind off this conundrum.

Tscarborough 05-15-2014 07:13 PM

Re: limestone vs. brick construction
 
Limestone is not lime.


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