If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.
Potters clays are really specialized. They are also really expensive, compared to bricks. Grog is crushed, fired, clay, and it's used in a thicker clay body to prevent cracking. Cracking is a bad problem when making thick slab based pottery.
In any event, potters clays are classified by the cone, or temperature, they are fired to. Since a mud oven will never get hot enough to vitrify, you're probably just as well off with river mud.
Grog can also be sand (albeit crushed) - add straw and you now have either adobe or cob. The answer to has anyone done it is basically yes since cob/adobe/earth ovens are all made of a clay/sand mix. As for commercial clay, dmun is right. It's much more expensive.
I've never read of anyone bothering with a true clay body (mixture of clay types to provide the working clay) for any type of earthen oven. In cob, the ratio of sand to clay is at issue, not the clay body.
As for how well the ovens perform, they do quite well.