why are the brix readings of fermented solutions usually higher than unfermented beverages
Brix Alcohol has a higher refractive index (1.361) than water (1.333). As a consequence, a refractometer measurement made on a sugar solution once fermentation has begun will result in a reading substantially higher than the actual solids content. Thus, an operator must be certain that the sample he is testing has not begun to ferment. Brix or Plato measurements based on specific gravity are also affected by fermentation, but in the opposite direction; as ethanol is less dense than water, an ethanol/sugar/water solution gives a Brix or Plato reading which is artificially low.
Alcoholic spirits measure The 1963 Act formalized the legal measures by which spirits and other alcoholic beverages should be dispensed, namely 1/4 gill (35.5 ml), 1/5 gill (28.4 ml) or 1/6 gill (23.7 ml), but this was replaced in 1985 by 25ml and 35ml for single measures, with double measures of 50ml or 70ml being permitted in 2001. Landlords have the option to decide which quantities they sell, with the difference being caused by historically larger measures being used in Scotland and Northern Ireland.