Good clay

Hi, so what do I have to do to make a good clay?
I'm using Clay Trough now and it is coming out as 0% purity.
I found some 3% lime but the milk of lime is 0% still.
So do i have to look for water to match my lime?
Or maybe you cant clay through good clay and i have to find a deposit with purity >0?
My Pots and Pans skill is 30.
I'm using Clay Trough now and it is coming out as 0% purity.
I found some 3% lime but the milk of lime is 0% still.
So do i have to look for water to match my lime?
Or maybe you cant clay through good clay and i have to find a deposit with purity >0?
My Pots and Pans skill is 30.