In this work we propose a novel separation technique based upon the control of the threshold for motion of different classes of particles in yield stress ﬂuids. The principle is demonstrated by observing the motion of particles under the inﬂuence of a centrifugal force in a weak gel. Here we develop calibration curves of the force required to initiate motion in a gel under numerous conﬁgurations of the particles. Demonstration separations of bidisperse suspensions are reported. Here we achieve complete separation of dilute suspensions based upon length, diameter, or density.