Eleven experiments were conducted using a 22full-factorial central com-posite design with three central and four axial points (Montgomery,2000), and resulted in eleven film formulations tested as shown in Table 1. The behavior of the system was fit to a second order equation: Yi = ˇ0 + ˇ1CG + ˇ2CF + ˇ12CGCF + ˇ11CG2 + ˇ22CF2