<p>A tensiographic drophead comprises a quartz body 10 having a terminal surface 18 with a peripheral drop suspension edge 20. A liquid feed bore 14 extends through the body for supplying a liquid to the terminal surface to form a drop 32 whose outer edges are suspended from the suspension edge 20. At least two light guides 26, 28 extend through the body for respectively transmitting light into and collecting light reflected internally from the drop. The light guides terminate above the plane containing the suspension edge such that the intensity of the reflected light has a significant second order reflection peak.</p>
