So these last few weeks I have been working on building a cob oven. I cant say I followed a particular set of plans, just reading as many how tos and forums that I can. Last week I tried doing a big burn but ran in to some issues.

First I started getting some cracks on the inside of the oven, I did my best to fill these when it was cool and I will continue to do so, I dont think these are leaking smoke.

When I made a big fire, I had little wisps of smoke start to come out of the top. They were fairly inconsistent, when the oven had a lot of smoke coming out of the door, nothing from the top or the other way around. Sometimes at the same time.

The first layer was a 1:1 mix of clay dirt to sand, I dont know the exact percent, but I believe around 25%. Second layer was the same 1:1 plus saw dust and stray. The inner radius is 22.5" and a height of 16". The door is 12" wide and 10" tall.

The other problem was heating it, after about an hour and a half of heating it with a very large fire, it only got to around 500 or so degrees. Is the door the wrong size? We did use pine for this one, does using a hard wood make such a big difference?

For a more detailed view of how I made it, I made a video on how I did it if you want a to see the steps I did. (and probably various errors):  https://youtu.be/PkfRTFKJ8sU