Prepared masa can be used for making tamales if it is light and fluffy. A simple test is to drop a ball of the prepared masa in water. If it floats, it is ready to use. If it doesn’t float, add more lard and test again.
Masa begins as dried corn kernels. The kernels are softened with the outer hull removed and ground. The softening allows the corn to bind together to make a dough called masa. Masa harina is the dried form. When buying prepared masa, check the label for “para tamales” or “para tortillas.” Prepared masa “para tortillas” is a much finer texture.