Cob: cob mix

[John Fordice]

Natalie,
Try adding mixing sand into the  wet clay until the mix will no longer
hold together .
Keep track of the proportions as you do this.
Then reduce the sand content just enough to allow the mix to hang
together when you do a toss test.

( Toss Test = make a hardball or so size ball of the wet mix and toss it
up a few feet into the air & let it impact into you open palm.  If the
ball breaks apart on impact, the sand content is too much.  Reduce the
sand content till the ball remains intact on impact. )

This will give you the maximum sand content you need to add to your
basic clay material and should give you the strongest mix.

It's not necessary to add straw to these tests.

I usually make test bricks that are closer to 1.5" thick.  Try this mix
proportion technique and do a few different thickness test bricks of the
stongest sand / clay mix determined as described above.  Let us know
what you discover.

john fordice