How to Use a Refractometer to Brew Beer Easy-to-Use Refractometers have become the new standard for beer measurement ur love of beer, one of the oldest volume as determined through the world and were more cultural than products in the world, dates distillation. significant. O back some 7,000 years. From its humble beginnings as an industry, Primarily, measurement is about Later, around the turn of the 20th necessity warranted the creation of quality control. For instance, even century, it was found that various standards and methods for though beer in the US is taxed based on refractometers offered a superior measurement. The need for standards its volume, it is still industry best method for the measurement of sugar was driven by simple commercial practice for the beer chemist or brewer and alcohol compared to the requirements for accurately measuring to keep accurate records of beer hydrometer. Many of the units of the extract content of the wort for measurements. measure originally developed for determination of excise taxes. simplifying hydrometer readings were Development of a Cohesive adapted as refractometer scales. Most of these methods initially relied on the hydrometer, or some other Measurement Standard The most common international primitive measure related to specific brewing units of measure consist of gravity, to provide an indication of sugar Archimedes was the first to observe Brix, °Plato, Specific Gravity, Brewer’s or alcohol concentration. However, the relationship between the densities Points, Balling, and Total Dissolved refractometers have now proven of liquids sometime between 267 and Solids (See Appendix I). themselves to be useful tools for the 212 BC. Relying on the Archimedes brewer. principle, Hypatia of Alexandria, one of Common Beer the first recorded female scientists, Measurement Terminology This paper is intended to help you invented the first hydrometer between get the most out of the refractometer 390- D. As an instrument, the that you currently own and to help you hydrometer was largely ignored until it For those new to brewing, there are decide what is most important in gained415 widespreadA acceptance after some common brewing terms that are selecting a refractometer for future use. reintroduction by English scientist important to understand with respect to Robert Boyle in the late 17th century. beer measurement. These terms are Why Measure Beer? covered only briefly here. The reader In subsequent centuries, a series of should be familiar with these concepts improvements to the basic hydrometer and can find much more written about In the US and Canada, beer is were made with the intention of them in other publications. primarily taxed based on the volume providing a simplified system for the removed from the brewery. In Europe, measurement of specific gravity by Wort is the liquid extracted from the however, taxation is country dependent unskilled persons. These improvements mashing process during beer brewing. and is either based on the °Plato per related more to differences in units of Wort contains the sugars to be hectoliters (strength of original extract measure than to the actual principle of converted to alcohol during by volume) or, in some cases, the measurement. fermentation. alcohol content per hectoliter. Different units of measure for Specific Gravity (D20/20) is the For most tax purposes, it is often specific gravity are akin to the relative density of a fluid at a reference nt difference in reporting temperature in temperature, relative to the density of alcohol by volume. However, in the UK, assumed that 1 °Plato ≈ 0.4 perce degrees Celsius vs. Fahrenheit. Specific water at a reference temperature. It can beer tax is calculated by multiplying units of measure became standard in a be measured using either a hydrometer hectoliters by the declared alcohol by particular beer making region or part of or refractometer with an appropriate Copyright © MISCO 2014 scale, providing fermentation has not Alcohol by Volume (ABV) is simply Refractometers yet started. the percentage alcohol per volume of beer. A refractometer is an optical instrument designed to measure the Original Extract (OE) is the mass in concentration or mixture ratio of water grams of sugars in 100 grams of wort, Hydrometer vs. prior to fermentation, as measured on soluble fluids. It measures refractive the °Plato, Brix, or dissolved solids scale. Refractometer index, the speed at which light passes through a liquid. The denser the liquid It can be measured directly on certain the slower the light will travel through refractometers and hydrometers or The hydrometer is based on it, and the higher its reading will be on converted from Original Gravity. Archimedes principle that a solid the refractometer. Like hydrometers, suspended in a liquid will be buoyed up many different scales are available that Original Gravity (OG) is directly by a force equal to the weight of the convert refractive index into a unit of related to OE, with the exception that it liquid that it displaces. Therefore, the measure that is more meaningful, i.e., is a measure of specific gravity at a lower the specific gravity of the Brix, specific gravity, °Plato, etc. given reference temperature prior to substance, the lower the hydrometer fermentation. It can be measured will sink. Refractometers designed for field directly on certain refractometers and use are usually rugged and portable. An hydrometers or converted from OE. Hydrometers are usually advantage over the hydrometer is the constructed of glass or plastic. They relatively small sample size that is Apparent Extract (AE) is related to often have a cylindrical stem with a required for testing. This also saves time Final Gravity, and represents that measurement scale sealed inside and a required for cleaning and sanitizing the portion of the OE present as residual carefully weighted bulb to make it float hydrometer equipment. sugars which were not converted to upright. In use, the hydrometer is gently yeast biomass, ethanol, or CO2 during lowered into the liquid until it floats Although refractometers are also fermentation. It can be expressed freely. The reading is taken at the point dependent on temperature, certain interchangeably as °Plato, Brix, or where the surface of the liquid (the refractometers are made with automatic dissolved solids and is usually meniscus) crosses the scale on the stem temperature compensation; in fact, you determined through calculations based of the hydrometer. shouldn’t rely on results from a on OE, or specific gravity as read on a refractometer without temperature hydrometer. Although the hydrometer is affected compensation. by the density of the fluid, it may have a Final Gravity (FG) is a measure of scale inside with any particular unit of Brewers are likely to encounter two specific gravity, at a given reference measure that is related to density. One different types of refractometers; temperature, at the conclusion of important point to note is that whatever Traditional Analog and Digital fermentation and is directly related to the unit of measure, the hydrometer Handheld. AE. Specific gravity readings can signal scale is only valid at one particular the end of fermentation when they stop temperature. Hence, they must be used Traditional Analog moving. FG can be measured directly on in conjunction with a thermometer, and a hydrometer or calculated based on OE any variation from the reference Refractometer and AE. temperature must be noted and The traditional analog refractometer compensated for. is comprised of lenses and prisms that Apparent Attenuation (AA) is a focus a shadowline on a tiny glass reticle measure of the amount of sugar Also, due to the nature of the with a scale etched on it. You point one consumed by yeast during fermentation hydrometer, a relatively large sample end at a light source and look through and the extent to which the yeast has size must be used so that the the other end. The scale inside is likely been able to successfully convert hydrometer can float freely. Since the to be Brix (a measure of sucrose), wort fermentable sugars into ethanol and hydrometer is made of glass, great care specific gravity, or both. These units, CO2. It is calculated as the drop in must be taken to keep it from breaking. likely made in China, can be found for as extract during the fermentation divided Obviously, the hydrometer is not $60.00 and are aimed at by the OE. designed to be used as a field the home hobbyist. little as $35 to instrument. www.misco.com/beer Page | 2 REV140407-1 The Traditional Analog Refractometer can be further split into 30 two categories, those with and without automatic temperature compensation. However, since refractive index (the 25 underlying method of measurement) is very temperature dependent, refractometers without temperature compensation should not be considered. 20 However, analog refractometers with temperature compensation are compensated based on sucrose, which is problematic since there is so little 15 sucrose in wort. Digital Handheld Refractometer 10 The second type of refractometer is the digital handheld refractometer. Brix % DS Beer Digital instruments read the refractive index of a fluid and use an internal scale 5 to convert refractive index into a useful unit of measure, such as Brix, Plato, or FIG. 1 specific gravity, and display that value on an LCD display. Like analog 0 refractometers, there are many different 1.3330 1.3430 1.3530 1.3630 1.3730 1.3830 brands of digital refractometers whose quality and accuracy can vary widely. solution consists of water, sugar, and ethanol and the three components The Truth about Refractometer How can I use a interfere with accurate specific gravity Correction Factors measurements. That said, the Refractometer for Beer? In Figure 1, you can see the refractometer is still a valuable tool difference in the relationship between during and after fermentation.