The central part of the setup was the crystallisation cell that held a cuvette containing the solution during the measurements. The cuvette was manufactured by Hellma (Southendon-Sea, UK). It was made of two pieces of z-cut quartz (each 1.5 mm thick to avoid etalon reflections) glued together using EP220 epoxy (Fiberdur, Aldenhoven, Germany) with an outlet on each side giving a pathway of solution. The channel was 24.5 mm long and 100 µm thick, and a schematic drawing is shown in Figure .