Methods for mixing fluids including etanercept include providing a tank having an impeller with a 10 inch blade diameter disposed therein, filling a tank with a liquid composition comprising etanercept and one or more buffers to a level within the tank to cover the impeller, and operating the impeller to mix the liquid composition to a homogeneous state while maintaining a maximum shear stress imparted on the mixture of fluids at 125,000 s.sup.1 or below.

A stirring blade that stirs a fluid by rotating around a rotary shaft, in which a flow of the fluid in which a Reynolds number is 300 or more and a ratio of a deformation rate tensor with respect to a velocity gradient tensor of the fluid that is a sum of the deformation rate tensor and a rotational speed tensor is 0.8 or more in a region of 5% or more in the flow is generated.