In the past I thought the the typical way of measuring a materials density is to measure its volume and then weigh it. As there are obvious difficulties and flaws (fluids can evaporate during measurements, volume size errors) a different way is to use a refractometer which uses a fluids index of refraction to estimate it’s density/etc. These all have to be calibrated for the particular working fluid and I have one made for ethanol. It is a good tool and a non destructive small sample way of finding the alcohol %.
After calibration at the low and high end I was able to measure the alcohol% in various drinks and found some that under deliver. One key thing to note is to never take measurements blindly as alcoholic beverages that have high sugar content can artificially change the alcohol% as it changes the fluid density.
