Sodium silicate; Cob Oven Interior

Hey folks,

Question for the hive mind. Anyone have experience treating the interior of their cob oven with sodium silicate? I've read good things and understand the concept. Specifically, has anyone treated the interior POST firing? Does it still function well or does the soot on the inside impede the impact of the treatment at all?

Thanks everyone!

Hi Travis;
I don't have a cob oven yet, but I have played with water glass (sodium silicate) on my rocket mass heater.

Years ago I had an all cast, fire clay perlite core.   The feed tube was constantly wearing and needing repair.
Brushing  the water glass on fired cob worked just fine as far as application goes. It would apply in your oven as well.
My opinion of it for a RMH is low as it only hardens the face and easily breaks a thicker piece if banged.

So I would say Yes, you can apply it in a used oven.
My question is , What are you hoping for?
Is your roof cracking / failing?

Here are some fun photos of the build for folks as well. It will likely get a lime plaster later.

thomas rubino wrote:Hi Travis;
I don't have a cob oven yet, but I have played with water glass (sodium silicate) on my rocket mass heater.

Years ago I had an all cast, fire clay perlite core.   The feed tube was constantly wearing and needing repair.
Brushing  the water glass on fired cob worked just fine as far as application goes. It would apply in your oven as well.
My opinion of it for a RMH is low as it only hardens the face and easily breaks a thicker piece if banged.

So I would say Yes, you can apply it in a used oven.
My question is , What are you hoping for?
Is your roof cracking / failing?

Thomas - My intention is to simply treat the interior for added durability from the beginning. Everything I've seen points me to, "why not". The stuff is cheap and have a friend with a ceramics studio. For a couple bucks to spray it on to the interior clay plaster and help prevent spalling and cracking seems well worth the few minutes and couple bucks. I guess I don't see any reason to not do it considering the benefits, even if small. I also see it as an opportunity to play around with yet another learning moment and experience it myself, always interested in new things/ways/techniques.

Hi Travis,   I can't see a lot of your pictures. The first 3 show up but then all of them but the last one don't show up. Would love to see your work!

EDIT - After I posted this your pictures magically appeared!  Boy you work fast.... Thanks!

Gerry Parent wrote:Hi Travis,   I can't see a lot of your pictures. The first 3 show up but then all of them but the last one don't show up. Would love to see your work!

EDIT - After I posted this your pictures magically appeared!  Boy you work fast.... Thanks!

Haha glad they worked! The photos span about two months but that included collecting all the stone from the mountains, digging the soil for the cob, and construction. All said the only costs so far are the cement mortar and fire bricks. The rest is salvaged and some well spent time. It’s been a fun project with my son. Final touches this week and we’ll fire it. Also working on a roof structure. Headed to the mountains today to cut posts.