West Coast Brewer Home Brewing Blog

Tag: specific gravity

Specific Gravity

In brewing, specific gravity is defined as the ratio of the density of a brewing liquid, such as wort or beer, as compared to the density of pure water. Typically either a hydrometer or a refractometer is used to determine the specific gravity of beer or wort.

 
A wide selection of home brewing hydrometers and refractometers can be found here:

Hydrometers and Refractometers
Below is a photo of a hydrometer, one of the instruments used to take a specific gravity reading in brewing.

Beer Hydrometed, Final Gravity Reading

Beer Hydrometer, Final Gravity Reading

Hydrometer

A hydrometer is an instrument used to measure the specific gravity of liquid in comparison to pure water. The hydrometer is important because it allows a brewer to determine several things:

  • When the mash is no longer contributing sufficient levels of sugar during a sparge
  • How much dissolved sugar is in the finished wort
  • If your beer has under or over fermented
  • Brew house efficiency
  • Original gravity
  • Final gravity
  • Fermentation progress
  • Fermentation completion
  • Alcohol by volume.

Below are three examples of different hydrometers that are available to brewers, including one used for determining your final gravity.

Beer brewing hydrometers for taking specific gravity readings such as Original Gravity and Final Gravity

Beer brewing hydrometers for taking specific gravity readings such as original gravity and final gravity.

 

Here is the final gravity reading from a hydrometer that also registers temperature so that corrections can be made if the beer is too hot or too cold.

Beer Hydrometed, Final Gravity Reading

Beer hydrometer showing a final gravity reading.

Final Gravity

The final gravity or FG of a beer is the beer’s specific gravity once fermentation has completed. Once a brewer has measured the final gravity, it can be compared to the original gravity and the ABV or alcohol by volume can be calculated. The final gravity of a beer is typically taken using a hydrometer or refractometer. Specialty final gravity hydrometers are available to allow you to take a more accurate reading of your final gravity if desired.

 

Below are three different types of hydrometers used for taking the specific gravity readings of beer.

Beer brewing hydrometers for taking specific gravity readings such as Original Gravity and Final Gravity

Beer brewing hydrometers for taking specific gravity readings such as original gravity and final gravity.