Shu Lim

Hi Guys,

Cob oven question.

I found what I thought was "sand" to use to build a cob oven, but it turns out that it is likely to be a mix of lime and sand. It's a white powder, and sticky when wet and easily washable. I've already made a batch of cob with it and right now, it is looking like a very white cob.

I've seen this lime plaster used externally on cob ovens. But little info on lime plaster internally, or incorporating a significant amount of lime together with your cob where it will be in direct contact with the heating surfaces. (Expecting oven temps to get to about 500-600 degrees Celsius)

I'm just slightly concerned from a safety perspective. I don't want to be using anything that could leach into food that is being cooked etc.

Otherwise I'm probably going to redo the whole thing with proper "brown cob".

Cheers,
Nick

I'm in the same situation as you. I'd do a cob floor and put in a 400x400x20mm bluestone slab which will become your oven floor. No sandy residue. Bluestone generally heats well and is cheap to find in NZ at your local Bunnings or any paver shop. They tolerate high temperatures very well. If it cracks, just pull it out and put in a new one. Just make sure your opening is more than 40cm so you can fit it in. Otherwise you may have to cut it down to size with an angle grinder and a diamond cutting disc. It worked well for me.