cob dreams and questions

[jimmyg]

I just got done the dream and semi planning stage on building a cob oven. I just made a dome mold and neck mold out of cut cardboard and paper machete'. Being there is 6" of snow and temps in the teens and 20s in the morning. I am looking at 3 weeks before ground thaws. I have read a book on earth ovens and doesn't say whether to mix the sand and clay when its dry or do u wet the the clay first and then mix together? I' ve also made my arch door mold. I am not planning a chimney because we will b only using it sparingly in season. If I do beer bottles with slip and then perlite and slip is this overkill under bricks?

[david s]

An easy way to make the cob mix is to dig the clay, place it on a large plastic tarp, then add water sand and a little chopped straw while stamping on it to mix. Periodically lift each corner to get the stuff back in the middle.Bare feet is good because you can easily feel any larger rocks (or broken glass ) to discard.

[jimmyg]

Thx Dave what about using dry grass instead of straw for second strength layer?

[david s]

Yes sure, but you don't want too much it's just for reinforcement so keep the mix really dense. If you use it for an insulating layer then use lots of it chopped into short lengths (a tomahawk works well) with just enough slip (liquified clay) to make it stick together with plenty of air spaces through the mix.