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Tag: gravity

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.

 

 

Amylase

Amylase is an enzyme group that is responsible for hydrolizing\converting starches into sugars. The two primary amylase enzymes are alpha amylase and beta amylase, which digest and break down the polysaccharides into smaller disaccharides and then monosaccharides. To help facilitate the breakdown of unfermentable sugars, amylase may be added to fermentation at the same time you pitch your yeast. This will create a lower final gravity and a dryer finish.

Alcohol by Volume ABV

Alcohol by volume (ABV) represents what portion of the total volume of a liquid is alcohol.

 

To calculate the ABV of a beer,  you will want to subtract the Final Gravity from your Original Gravity and multiply by 131.

 

The following is an example of how to calculate your alcohol by volume, assuming that your original gravity was 1.055 and your final gravity reading was 1.012.

 

Here is an example: 1.055 – 1.012 = 0.043 x 131 = 5.633%
In this example your alcohol by volume worked out to 5.633%.

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