There's no denying it, home brewing beer is a science with many important factors to consider. A hydrometer is a wonderful tool that can help ensure a better beer each and every time.\n\n\n\nSo what is a hydrometer exactly? A hydrometer is a device that measures its own displacement of liquid and therefore can help you calculate the density (sugar content) of your beer or other alcohol. Using these measurements it is possible to tell when fermentation has ended and calculate the alcohol by volume (ABV) of your beer.\n\n\n\nIs a hydrometer an essential piece of kit? Certainly, but it is in theory possible to do without one. However, you are going to have to calculate a lot more data then you have to.\n\n\n\nHow does a hydrometer work?\n\n\n\n\n\n\n\nA hydrometer is an instrument with many different applications for different industries, but in short, it measures the specific density of a liquid. The specific density (SG) is the relative density of a liquid compared to water. In the case of alcoholic drinks, this density is determined by the presence of sugars in the liquid.\n\n\n\nA hydrometer is a longish cylindrical device with a bulb at one end. It's designed to float freely in the liquid it is introduced into and the point at which the stem portion meets the surface of the liquid, this will give us our specific gravity reading.\n\n\n\nThe hydrometer we use in brewing beer is more precisely called an alcoholometer or "Proof and Tralles" hydrometer, but let's just refer to it as a hydrometer because we aren't real scientist now, are we?\n\n\n\nMost hydrometers used in brewing beer will give you a "potential" alcohol content right on the stem, which has been calculated from pre-calculated specific gravity. However, most of us will just need a Specific Gravity reading of between 0.98 -1.12 \u00b0SG (usually measured in \u00b0BX). From here, we need to make some calculations of our own.\n\n\n\n\n\n\n\nHow to read the hydrometer\n\n\n\nMost hydrometers come as a little kit with the hydrometer itself and a sample container. If it doesn't, make sure you get yourself a test jar with a nice wide base to avoid tipping (this will break the hydrometer). The hydrometer designed for alcoholic beverages will give you two readings, a Brix (\u00b0BX) and potential alcohol (measured as ABV).\n\n\n\nIn order to use your hydrometer to measure the specific density of your wort, you first have to extract a sample of the liquid to use. DO NOT put your hydrometer directly into your main batch as this can introduce bacteria, especially during fermentation.\n\n\n\nInstead, get yourself a turkey baster or "wine thief" to take a small sample to test. You need about enough to fill a test-tube or small upright container. \n\n\n\nSlowly introduce the hydrometer into the liquid and make sure that it is floating freely. When you are sure that it is, look at where the surface of the wort meets the stem of the hydrometer. You'll notice a sort of bubble effect (meniscus) which occurs when light is refracted through the liquid. Take a reading from the bottom of this bubble and not the top. \n\n\n\nWhat can I use a hydrometer for in my brewing process?\n\n\n\nThe hydrometer is used to tell us the density of the wort during the brewing process. This basically means how much extra stuff is in the water contained in the wort. That extra stuff is sugar which has been released from the grain starches during mashing.\n\n\n\nWhy is that important information exactly? Well, beer is made through yeast converting sugars in the wort into ethanol and carbon dioxide. The density of our wort can tell us how successful the yeast has been and whether fermentation is completed or not.\n\n\n\nThere are two key measurements that need to be made and noted. The first is before we introduce any yeast into the wort and just after the mashing phase. It's called Original Gravity (OG). It tells us where our wort began in terms of density and will be the level all other measurements are compared to.\n\n\n\nThe other significant measurement we make is after fermentation has ended (although you need a hydrometer to help you determine this too). It is called the Final Gravity (FG) and will give us the final density reading before we proceed to the bottling or kegging stage. \n\n\n\nBy using these two measurements we are able to calculate the alcohol by volume (ABV) which will tell us the level of alcohol in our beer. This is, of course, some very important information if we want to gauge the strength of the home-brew.\n\n\n\nIn addition to finding out the Final Gravity of this particular batch, using a hydrometer and making detailed notes throughout your brewing process will help you consistently produce the same quality beer (as much as can be expected) or to improve the beer with each attempt.\n\n\n\nIf you have a higher level FG than expected from your recipe instructions, this could indicate that fermentation hasn't ended or has "stuck". This is a really important way in which a hydrometer can help the brewer determine the level of fermentation in their beer. If this is the case and you think your fermentation is not going as it should, then check out my article on fermentation.\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n Plan your next Beer Creation?