A refractometer is used to measure the
specific gravity or the amount of sugar in an unfermented liquid. It
requires a much smaller sample than is needed when using a
hydrometer. A refractometer cannot be used after fermentation
because the alcohol distorts the refractive rays.
With just one drop, you can measure the
brix (sugar content) in grapes. A necessity in the vineyard for
monitoring ripening grapes.
Brewers, do you always hit your target
gravity? Cooling a large enough sample to take a hydrometer reading
can be a bit of a challenge. A refractometer allow you to get
instant gravity readings at any time during the boil or the run off.
By taking readings during the process, you can add more water during
the boil or boil longer to achieve your desired starting gravity.