Brewing beer has been an artform of sorts for around 5,000 to 7,000 years now and while the process hasn't been always the same the end product has. The brewing process today is a new one and so is the equipment and instruments used in it. One of the more important brewing instruments is the hydrometer. A brewing or alcohol hydrometer is used to measure the density and specific gravity of the beer.
The latter refers to the liquid's density compared to water and you get it by dividing the density of a liquid (beer) and the density of water. Hydrometers are long glass cylinders that have a weighted bulb at one end. This bulb allows the hydrometer of float upright when taking measurements. They work by displacing some of the liquid and this sample is used to measure its density at a specific temperature. But hydrometer has other uses too.
Common Uses
Sugar & Alcohol Content
In the brewing process, a hydrometer is mainly used for measuring sugar and alcohol content as both are important for getting the style of beer you're after. Sugar is known to increase the density of a liquid but it is also the precursor for alcohol content. Using a beer hydrometer to measure the sugar content prior to fermentation will tell you how much alcohol there's going to be when the sugar converts into it.
Soil Density
There are special types of hydrometers that measure the density of small soil grains. These can help determine the size of soil particles which is an important part of soil analysis.
Fat Content
Going back to liquids, hydrometers are used when making milk and milk products. This is where measuring the density of the milk/ milk product can tell you a lot about its fat content as well as the purity of the milk/ milk product.
Types of Hydrometers
Triple Scale
The most common and also most affordable beer hydrometer uses three different scales. These scales measure, potential alcohol, specific gravity and Brix (balling scale) degree. Although basic, triple scale hydrometers are able to measure a wider range of specific gravity which makes them suitable with the majority of batches.
Thermohydrometer
This is a hydrometer with a thermometer built into it. This way you don't need to use two different instruments to get accurate measurements. The thermometer on the thermohydrometer also helps provide more consistent measurements.
Precision
This type of brewing hydrometer has a smaller scale than your regular brewing hydrometer hence why it can do more precise readings. But if you're planning to brew different varieties of beers you'll need multiple precision hydrometers. This is because they have a smaller measurement range.
Digital
The newest hydrometer on the market that can measure density, temperature and specific gravity than a traditional one is a digital hydrometer. There's no place for human error with these instruments and they are also capable of calculating alcohol content. The main benefit is that with a digital hydrometer that it can adjust itself for temperature differences when you're measuring specific gravity.
Tips for Using Hydrometers
Test
The first you need to know when using a hydrometer is to test it. Even if you have a brand new one you should ensure it works properly before you take a sample of wort. To do this fill a jar with distilled water with the corresponding temperature of your hydrometer. If the hydrometer is calibrated correctly it should give you a reading of 1.000 on the specific gravity scale.
Test Temperature
No, you don't need to test the temperature, in fact, you need to know the correct test temperature. When testing a sample you'll need to ensure that it's at the correct test temperature for your hydrometer. If it isn't, make sure to adjust the temperature of your specific density so it can compensate for the change in density.
Space & Cleanliness
Keeping the jar and hydrometer squeaky clean is as important as the ingredients themselves. If there's dirt inside the hydrometer or jar it can tamper with the sample and prevent it from rising evenly thus making for an inaccurate reading. By giving your hydrometer enough room to float in the sample without rubbing against the edges of the jar you will ensure for an accurate reading.
Meniscus
When you're reading the hydrometer make sure that you are at eye level with the liquid and reading horizontally across the surface of the liquid. This way you will read the results more accurately as the liquid clinging to the edges can make for a curved meniscus.
No Over-testing
While testing is a great way to see how if your hydrometer is working properly and if the batch is staying on its course, you shouldn't overdo it. Why? Because every time you take a sample you are exposing the brew to bacteria and air which can easily contaminate the brew. If you're using a traditional hydrometer make is to test your wort as little as possible to reduce the risk of contamination. No matter how many tests you do if your batch gets contaminated everything falls into water.
