Refractometers are measuring instruments that put the phenomenon of light refraction to practical use. They are based on the principle that as the density of a substance increases (e.g., when sugar is dissolved in water), its refractive index rises proportionately (how much the straw appears bent). This means that the refractive index of a solution, e.g., water or sugar, is proportional to the concentration of sugar. When a straw is placed into a glass of water, the straw appears bent. If the same straw is placed in a glass with a water or sugar solution, the straw should appear even more bent. This phenomenon is known as the Principle of Light Refraction.
Handheld refractometers are simple to use. Only place one drop of your sample on the prism and read the result on the scale immediately. Each refractometer is calibrated to measure at 20°C (68°F), has an adjustable focus, a clear reading of the scale, and can be calibrated by screw. Models with Automatic Temperature Compensation (ATC) between +10 and +30 °C are suitable for applications where the temperature of the samples varies greatly, e.g., for sorbets, jams, fruit juices, and ice creams. They are provided in a box, with a cloth, screwdriver, pipette, pocket case, and instructions for use.