Fireclay inside the dome.

[James Meloy]

I have built a Cob oven with bench seats on both sides(which is nice) and I am going to cover the inside of the dome with Fire clay and I was wondering about what thickness I should apply inside. Thanks!

[david s]

What are you trying to achieve by coating the inside with fireclay?
I don't believe that it will make an ounce of difference in making your dome more refractory. a coating on the inside may help to tidy up the surface in which case a brew of equal parts fine sand, white cement, lime and any powdered clay will do fine, but needs to be applied to the inside when it is neither too damp nor too dry. Straight clay is more prone to shrinkage and flaking

[dmun]

I agree with David. Coating the inside of your dome sounds like a flaky mess in the making.

[James Meloy]

What I want to do is take care of some of the dome which has given away a very small bit under the water coil, and I figured if I can take care of that and make it smoother and less flakey It would be ok. Not for the extra refractile properties. And if so, then how long to cure it? Much thanks!

[azpizzanut]

Hello JM,

Mix up more of the same cob mix but a little thinner and without straw. Smear it on in thin layers. If the oven is already dried then it may not work since the dry cob will suck moisture from the slurry. Try it in a small section first to see if it adheres.

Best of luck,

[James Meloy]

Thanks Bob, I'll give it a check. I was thinking about the thin straw-less mix also. Still leaning towards the clay(thin) about1/4 inch. from what the dome is now, which is a great size.
James

[azpizzanut]

Hi James,

How are you coming along with your patch?

Cheers,

[James Meloy]

Hey Bob- I did the work today! So now the fun part of waiting. It's killing me that it's not in use right now!
Take it easy Bob-

James

[david s]

"a brew of equal parts fine sand, white cement, lime and any powdered clay will do fine, but needs to be applied to the inside when it is neither too damp nor too dry. Straight clay is more prone to shrinkage and flaking"[/QUOTE]

Adding a slurry of the same mud mixture to the already dry dome interior is not likely to be successful because wet clay does not stick to dry clay. That is why I suggested the brew above, which has a much lower clay content and therefore has less shrinkage. It is a tested brew that works. Good luck with what you've done.

[azpizzanut]

James Meloy,

Hi James, can you report on the success of your patch? I'm sure others would like to know how you did it too.

Cheers,