Tuesday, July 16, 2013

Hydrometer Readings

When you are brewing beer, wine, mead, cider, or anything else with alcohol a hydrometer is as close to a necessity as you can get. Sure, we have all brewed a batch or two without one, just waited till the airlock stopped bubbling, then waited a little longer, but this is not ideal. Without reading your specific gravity, you can't really be sure that your beverage has fermented all the way, and you wont be able to tell what your alcohol level is. A hydrometer is the least expensive way to read your specific gravity. 
Specific gravity is a measurement that shows you the density of your liquid. The illustration below demonstrates how to read your hydrometer. Fill the container it came in, or a test jar with the liquid you would like to measure (at room temperature). The Hydrometer will float in the liquid. Read the number at the top of the liquid. Surface tension will try an pull up on the liquid touching the glass, but make sure you read the number where the liquid would be if it were a perfectly flat surface. The diagram to the right is illustrating a Specific Gravity of 1.046, which could be the Original Gravity (density before fermentation) of a 4.6% ABV beer.
Brewing Jargon
We home brewers refer to a gravity of 1.010 as "ten ten", and 1.020 as "ten twenty, and so on.

As a rule of thumb
<1.010 = Very Dry finished beverage
  1.010 = Common F.G. for finished beverages. Well fermented, slightly dry finish.
  1.011 - 1.020 = Still OK. Finishing a little sweet.
  1.021 - 1.030 = Super sweet. Possible stuck fermentation.
Alcohol Content
Take your O.G. and Subtract your F.G (1.045 - 1.010 = 0.035)
For Alcohol by Weight "ABW" Multiply by 105 (0.035 x 105 = 3.68% ABW)
For Alcohol by Volume "ABV" Multiply your "ABW" by 1.25 (3.68 x 1.25 = 4.6% ABV)
For a quick gauge of ABV just take the last two digits of your OG and move the decimal. In the above example you started with 1.045, this is approximately a 4.5% beverage.

Stuck Fermentation
If you have determined that your Starting Gravity should be at 1.050 and your Final Gravity should be at a 1.010 but your airlock has stopped bubbling for a  week or more and you have only fermented down to 1.030 you probably have a stuck fermentation. Here are some trouble shooting tips:
1: Make sure your beer/wine temp is between 65 and 75 degrees. If it is on the lower end, try and move it somewhere warmer and see if fermentation starts up again.
2: Try some yeast energizer. It is possible that the yeast has only consumed the simple sugars in your beer or wine and need some help getting to the harder stuff, energizer has essential nutrients to help get them going again.
3: Try re-pitching yeast. Yeast can fall out of suspension before they are really done working, some strains are more likely to do this than others, but any of them can do this. Putting the same yeast you started with can be a good way to start fermenting again, or using a highly attenuate neutral yeast like champagne will definitely eat left over sugars, but could leave your beer a bit more dry that you wanted 

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