The present invention relates to a device for determining the correct viscosity of a liquid, comprising member which either remains in or assumes a substantially upright or pre-determined position when placed in a fluid having at least the desired or specified viscosity and is unable to remain in a substantially upright or pre-determined position if a fluid has less than the desired or specified viscosity. The invention also relates to methods and uses of particular devices and is particularly suited to assisting patients suffering from dysphasia (or similar conditions) and who wish to thicken liquids to enable them to allow safe swallowing without aspiration to take place.