Abstract: A rheometer comprises a vessel mounted on a stand and a rotatable blade mounted above the vessel. A substance for rheometric assessment is put in the vessel. The rotor is advanced linearly into the substance while at the same time rotating. The blade is arranged with a profile such that there is substantially zero slip as it progresses, thereby minimising disturbance to the substance. The rheometric assessment is based on the axial force exerted as a result of the resistance of the substance to the progression of the blade through it.

Abstract: A rheometer incorporates a blade (1) mounted for rotation about an axis (2). The blade is of twisted form such that it has first and second regions. A first region of the blade (1) substantially at the axis of rotation (2) has a first angle formed by its surface with respect to a plane perpendicular to the axis of rotation such that the surface of the blade in the first region extends substantially parallel to the axis of rotation. A second region of the blade spaced from the axis of rotation has a second angle, different to the first angle, formed by its surface with respect to the plane perpendicular to the axis of rotation.