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-   -   Cob Oven (http://www.fornobravo.com/forum/f43/cob-oven-17427.html)

jagarvin 02-29-2012 09:55 AM

Cob Oven
 
Hi,
I have finished my first cob oven. I think I may have made an error with the inside of my dome. I used clay, straw, and sand mix. From what I have read now I should not have used that on the interior of the dome, but only clay ,sand mix. Is this going to be a problem?
Thanks

Rocko Bonaparte 03-10-2012 11:34 PM

Re: Cob Oven
 
The idea behind the straw is that it will insulate when used in significant amounts. In smaller amounts, the straw might actually help you out. The straw can provide some breathing room for everything to expand and contract. I didn't use straw here on mine so I can only speak generally about it.

david s 03-11-2012 12:05 AM

Re: Cob Oven
 
It won't matter, You might get the odd void right on the surface, but so what. Some of the straw that is close to the inner surface will just burn away. be sure you give it plenty of time to dry before attempting any fires. If it is fine weather try to let the sun and wind do most of the drying, but you will need to cover it if there is a threat of rain. A cover that allows air flow over the dome but shelters it from rain is good.

zeker 07-17-2013 01:26 PM

Re: Cob Oven
 
I too am confused about this.. in some spots it says.. use no straw on the first (oven) layer.. in others , it says to go ahead and use as ithe straw burns out and leaves small voids for expansion. watching the utube vids of folks building with cob, it seems they use the cob rite from the sand form.. color me confuzzled.

madKW 01-08-2014 03:29 PM

Re: Cob Oven
 
Hi all, I think its a case of get as much advise as you can then do what you think is best. I to am in the same boat ,no straw or straw ? I think I will use SOME straw but not alot
Cheers

david s 01-08-2014 03:54 PM

Re: Cob Oven
 
For the insulation layer use as much straw as you can with just enough slip (clay and water) to bind it. The insulation layer does not get hot enough to burn the straw.

Tscarborough 01-08-2014 05:43 PM

Re: Cob Oven
 
If you are going over a sand form, make your first layer with no straw, about 1/2" to 1" for a solid face, then continue adding straw as you build it up. The last 3-4 inches should be straw covered with a slurry of sand/clay mix for insulation.

madKW 01-08-2014 06:37 PM

Re: Cob Oven
 
Thanks for that.So 1/2"-1" for the face with no straw, then 3" with a modist amount of straw ,then 3"- 4" of lots of straw for insulation and finally a thin layer with little straw to render the dome . Does that sound about wright ? Thanks for the help

david s 01-08-2014 10:28 PM

Re: Cob Oven
 
Quote:

Originally Posted by madKW (Post 167928)
Thanks for that.So 1/2"-1" for the face with no straw, then 3" with a modist amount of straw ,then 3"- 4" of lots of straw for insulation and finally a thin layer with little straw to render the dome . Does that sound about wright ? Thanks for the help

Yes that's it. After you've fired the oven lots and the cracks in the outer shell have shown up, you can fill then with more mud and then render the whole thing with a sand,lime, cement coating. I use a 4:1:1:1 mix around 15 mm thick.

madKW 01-09-2014 12:24 AM

Re: Cob Oven
 
Grt thanks for that. I will finish putting the decomposed granite down this weekend so that will be the area done ,next will be the pizza oven stand then the oven its self.Soon I hope


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