What is a hydrometer?
How do I use it?

A hydrometer is a weighted glass tube filled with air. This device helps you monitor the brewing process of home-made beverages.

By floating a hydrometer in your fermenting bucket or floating it in a sample tube, filled with fermenting beer, during and after fermentation, you will be able to monitor yeast activation on sugars contained in your wort.. You will be checking what is called, specific gravity. Simply stated, specific gravity is a measure based on a number that somebody determined is a constant. Specific gravity measures density. When you add or subtract substance from the mixture (in this case, sugars) the change in specific gravity determines how the substance has been altered. For example, when you are done cooking your wort you will have maximum sugar density in your malt syrup, which the yeast will consume as your beer ferments. Before adding the wort to water first make sure it has cooled, as hot wort can kill yeast and give you inaccurate readings from your hydrometer. Water has a specific gravity of 1.000 at approximately 60 degrees Fahrenheit (15.5 Centigrade). When you add wort, the water is suddenly taken from a specific gravity of 1.000 to a higher number known as original gravity (original gravity is often stated as, O.G. in recipes). The O.G. value is made up of the specific gravity plus any dissolved sugars in the wort, which, of course, increase the density of the mixture.

The O.G. should be recorded when you take this reading, it will help you determine the alcohol concentration, as well as, "doneness", as it relates to the fermentation process of your beer. A second reading taken mid way through the fermentation process (after a few days or a week) will not only help advise you of how close you have come to the final gravity (F.G.) but it also lets you know if you are experiencing stuck fermentation, a symptom of inactive yeast.

The proper way to use a hydrometer is by spinning it in a testing tube or vessel. This spinning dislodges any air bubbles that might disrupt the reading. Be careful, these glass tubes are very fragile. I've broken two already due to carelessness. First and foremost, don't forget sterilization. Would you want a surgeon to do evasive surgery on your brain without washing up. Well, your beer can become irreversibly damaged if you don't take the necessary sanitizing precautions. Before dipping anything into the mixture don't forget to sanitize it and rinse it off well.

With a sterilized ladle or small measuring cup, fill the plastic tube that came with your hydrometer with cooled wort (60 degrees F.). Take a reading from the specific gravity scale and record it as the original gravity (O.G.). Remember, temperature changes will affect O.G. so leave some time for the wort to cool before you take a reading.

When you are taking a reading, be sure to view your results at the point where the meniscus is, that is where the value is read. The meniscus, for those who don't know, is the downward curvature of measured liquids. Surface tension causes liquids to adhere to external points outside of where a liquid lies, therefore, measurements are taken at the base of the curvature, where the bulk of the liquid resides.

Close your fermenting bucket and discard the test liquid, for it may introduce bacteria into the mixture, thereby, contaminating it.

When you either rack or check your beer follow the sanitizing steps discussed earlier for cleansing utensils. Compare your O.G. with the current reading. If you are using a recipe that states the O.G. and F.G., simply determine whether the mixture's hydrometer-specific gravity measurement matches up or comes close to what the recipe has stated. If it does, you are done, begin bottling your beer, and wait in anticipation for the finished product. If the beer has not reached the F.G. as stated or still seems to be moving along slowly, take heart your trusty hydrometer just told you that you are having problems with your beer fermentation. You either need to sit tight or maybe add some additional yeast or even an adjunct product called, yeast nutrient. Yeast nutrient sometimes helps kick a stuck fermentation beer back into action.