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Hydrometers: Introduction

Hydrometers are essential measuring devices used to detect the specific gravity of material. Note that specific gravity or relative density is defined as the ratio of the density of a material to the density of a reference liquid (e.g., water).

Interestingly, the invention of the hydrometer is credited to the famous philosopher Hypathia of Alexandria (370-415) and is based on Archimedes’ principle, according to which a solid body submerged in a fluid is buoyed by force equal to the weight of the fluid displaced by the body. While the design of the hydrometer evolved over the centuries, with some advanced models developed by the French chemist Antoine Baumé (1728-1804) and the English scientist William Nicholson (1753-1815), the most common type today consists of a glass tube with a weighted bulb (with mercury or lead shot) and a scale (with different scales for different uses; American Petroleum Institute gravity for petroleum products, Plato scale for brewing, and Brix scale for wineries).


Types of Hydrometers

Hydrometers are invaluable tools used to measure relative density. Note that such instruments are calibrated for different applications, depending on the liquid tested. Here we should note that there is a wide variety of specific gravity tools:

  • Lactometers: Lactometers or galactometers are measuring tools used to assess milk quality. Note that these instruments have a range of 1.025 to 1.035 g/ml.
  • Saccharometers: Saccharometers measure the amount of sugar in a substance and are widely used in the brewery. Note that low levels of sugar make a solution less dense and cause the bulb to float higher.
  • Alcoholometers: Alcoholometers (also known as Proof and Tralles meters) are popular meters used to assess alcoholic strength before and after fermentation. Their range varies between 0.98 and 1.12° specific gravity (SG).
  • Urinometers: Urinometers are invaluable instruments used in urinalysis (e.g., to measure a patient’s hydration levels). Note that these hydrometers have a range from 1 to 1.06 °SG.
  • Thermohydrometers: Thermohydrometers consist of a hydrometer and a thermometer and are ideal for assessing the density of petroleum products, a process in which the specimen is heated prior to analysis.
  • Antifreeze testers: Antifreeze testers are tools used to measure the ratio of antifreeze to water depending on the season.
  • Hydrometers for soil analysis: Hydrometers are also popular instruments for soil analysis, used when the grains are too small for sieve analysis. They can have a range of 0.995 to 1.038 °SG.
  • Aquarium hydrometers: Hydrometers can also be used to assess the salinity of aquariums and terrariums.


Choosing a Hydrometer

With a wide range of products for sale, choosing a hydrometer can be a challenging task. Prospective buyers should consider three major aspects: requirements, specifications, and costs.

Requirements: As hydrometers can be employed in a variety of settings, users should refine their research and production goals. Here we should note that there are three types of hydrometers on the market. Triple scale hydrometers are the most popular and affordable units available. They are multi-functional tools that can measure the specific gravity (0.00-1.170), Brix/Balling scale, and potential alcohol. Thermohydrometers, on the other hand, are used to measure both specific gravity and temperature. Precision units are also available. Note that they can measure specific gravity on a small and accurate scale (e.g., 1.000-1.070, 1.060-1.130).

Specifications: Apart from the specific type, users should consider the materials used. Note that glass hydrometers may break easily, and paper scales might be less accurate. Hydrometers equipped with mercury require special considerations as mercury is more hazardous than other materials.

Total costs: Before purchasing a hydrometer, users should decide on a budget. Additional accessories, such as testing jars or graduated cylinders, should be considered. Note that some units come with a testing jar (jars with a wild base are preferred).


Best Hydrometers

From Baume meters used for liquids denser than water and salt hydrometers to Tralle hydrometers that assess the percentage of ethyl alcohol and thermohydrometers, prospective buyers can choose from a wide range of products. Based on different parameters and user reviews, here are the best hydrometers for sale.

  1. Brewer’s Elite Hydrometer & Test Jar Combo

Brewer’s Elite Hydrometer & Test Jar Combo is an excellent hydrometer that comes with a 250 ml graduated cylinder, a storage case, a cleaning cloth, a brush, and a manual. Note that the unit has a triple scale: specific gravity (0.99-1.16), potential alcohol (0%-20%), and Brix Balling (0-35), which makes it suitable for numerous applications. With clear fonts and graduated color bands, measurements are easy to read and interpret, and alcohol by volume (ABV) is easy to calculate. With numerous features, this hydrometer is an affordable product ideal for making low-alcohol products, such as wine, beer, ale, and even kombucha at home.

  1. E-Z RED SP101 Battery Hydrometer

E-Z RED SP101 Battery Hydrometer is a highly accurate battery hydrometer made of unbreakable plastic and rubber that can resist tough treatment. Note that the unit has a range of 1.100-1.300. With its rugged design, this hydrometer is an affordable meter, ideal for technicians to check the state of battery acid.

  1. MEOMOU Hydrometer Alcohol Meter 0-200 – Proof Hydrometer Kit with Thermometer

MEOMOU Hydrometer Alcohol Meter 0-200 – Proof Hydrometer Kit with Thermometer is a great distillers hydrometer kit for assessing distilled spirits and high-alcohol liquor. With its practical thermometer (0℉-230℉) and conversion table, the unit gives accurate and clear readings, with a Proof measurement range of 0 to 200 and a Tralle measurement range of 0 to 100. Additionally, this hydrometer has a stable glass test jar, which is easy to clean (cleaning brush and cloth included).

  1. LabStock Master Distillers Hydrometer Test Jar

LabStock Master Distillers Hydrometer Test Jar is ideal for anyone looking for a high-quality test jar. This product is suitable for high-proof liquids, and there are no graduations in order to facilitate quick readings. Note that the jar is made of Borosilicate glass and has a three-inch diameter base with three contact points to resist tipping. With an innovative design, this cylinder is an excellent addition to any hydrometer kit.


Hydrometers: Maintenance Tips

Hydrometers are invaluable instruments. Thus, it’s not surprising that proper use, maintenance, and storage are crucial to guarantee long and accurate use.

  • Make sure to purchase a unit suitable for your production and research purposes. For example, Proof and Tralle units are designed for high ABV products, such as spirits (instead of beers and wines).
  • Before using your hydrometer, consider calibration and even testing the unit with distilled water. Note that calibration can be performed by official organizations, such as the National Institute of Standards and Technology (NIST) or any laboratory accredited by ISO/IEC 17025. Additionally, hydrometers should conform to different standards established by different organizations (e.g., E-126 – Standard Test Method for Inspection and Verification of Hydrometers).
  • Handle glass and mercury units with care to prevent incidents.
  • Always clean your unit to ensure accurate readings.
  • Last but not least, safe storage and transportation are crucial.
Hydrometers: Conclusion

Hydrometers are invaluable meters used to measure the specific gravity of liquids. These instruments are used in various applications, such as a brewery, mechanics, and research, to determine the weight and concentration of different liquids. From urinometers to alcoholmeters, we should note that there are different hydrometers designed for different purposes.

Before purchasing a unit, however, prospective buyers should consider three major factors: requirements, specifications, and total costs. Note that the three main types of hydrometers available on the market are triple scale hydrometers, thermohydrometers, and precision hydrometers. Accuracy, materials used, and additional accessories are also essential factors to consider.