Standard Reference Method, or SRM, is a method of measurement used to determine and define a beer’s color on a numeric scale using a photometer or spectrophotometer. The color of a beer is an important factor when judging a beer’s overall quality. Different beer styles are expected to fall into a specific color range, and the SRM is a way of measuring that. The lighter the color of a beer, the lower the corresponding SRM value will be, and, as expected, the darker the beer, the higher the SRM value will be. Beers range anywhere from 2 to in excess of 40 on the SRM scale. Below is a chart featuring the SRM value on the left with the approximate color and beer style example to the right.
West Coast Brewer SRM / Standard Reference Method Beer Color Scale
In brewing, specific gravity is defined as the ratio of the density of a brewing liquid, such as wort or beer, as compared to the density of pure water. Typically either a hydrometer or a refractometer is used to determine the specific gravity of beer or wort.
A wide selection of home brewing hydrometers and refractometers can be found here:
Hydrometers and Refractometers
Below is a photo of a hydrometer, one of the instruments used to take a specific gravity reading in brewing.
Beer Hydrometer, Final Gravity Reading
Recirculation is the process of pulling the wort from the base of the mash tun or lauter tun and recirculating it back on to the top of the grain bed. Recirculation typically occurs after the end of the mashing process. As the hot wort is recirculated through the grain bed of the mash, the grains act as a particle filter clearing the wort. As the wort is recirculating, it becomes cleaner and less turbid until finally it is clear and ready to be passed to the boiling vessel.
A pump is typically used to recirculate the wort at a steady and controlled pace. In the case where a home brewer does not have a pump available, the wort may be drawn into a container and slowly poured back on top of the grain bed. The process can be repeated until the wort has become clear. Additionally, rice hulls may be added to a mash as a means of boosting the filtration capability of the grain bed.
A wide selection of home brewing recirculation pumps can be found here:
Home Brewing Pumps
Wort recirculating in the mash tun, prior to sparging and transferring the wort to the boil kettle.
Wort Recirculating in the Mash Tun
Sparging is a brewing process that involves passing heated water through the grain bed of a mash to extract sugars from the crushed grains and adjuncts. Sparging is typically conducted at approximately 167° F to 170° F; if the temperature exceeds 170° F, the brewer risks extracting excessive amounts of tannins from the grains. If the temperature is too low, then the sparge will be ineffective at liquefying the remaining converted sugars from the grains. While the sparge water passes from the hot liquor tank to the mash tun, or lauter tun, via a sparge arm, the extracted sugars and water are being drained from the base of the vessel and relocated to the boil kettle in preparation for to upcoming boil.
This mash is being sparged at 168° F, while the beer is being transferred from the false bottom at the base of the mash tun over to the boil kettle.
Sparging in the mash tun, while wort is transferred to the boil kettle.
A session beer is defined as a beer with an alcohol by volume or ABV of less then 5%. The purpose of a session beer is to permit the drinker to enjoy multiple beers at a sitting without becoming overly intoxicated.
Beer sediment is the collection of solids that fall out suspension of a fermenting or conditioning beer. Sediment is mostly comprised of yeast, grain solids, hop solids, and adjunct solids. As the beer ferments or conditions, the dense solids fall and settle to the floor of a fermenter, conditioning vessel, or bottle, in the case of a bottle conditioned beer. The sediment is typically discarded, but if the yeast is still healthy, it may be recycled from the sediment to be used to ferment future beers.
Secondary fermentation is the process of transferring your beer to a secondary fermentation vessel to allow the beer to complete its fermentation cycle and condition in a clean environment. The primary reason for a secondary fermentation is to improve the taste of a beer. Towards the end of the primary fermentation, much of the yeast, beer solids, and hop solids will fall out of the beer and form sediment on the bottom of the fermenter. If left in contact with the beer too long, the dead yeast and solids can impart off or undesirable flavors upon the beer. For this reason, many brewers choose to rack the beer off of the sediment into a secondary fermenter to allow the beer to finish out fermentation, clarify, and condition.
The need for secondary fermentation is somewhat dependent on the style and characteristics of the beer that you are creating. For instance, if I am brewing an American wheat hefeweizen, I probably will not go through the trouble of a secondary fermentation because it is a relatively low alcohol beer with a low flocculating strain of yeast. This means it will ferment quickly, so the beer is only in contact with the sediment for a short period of time, and much of the yeast will remain in suspension with this style of beer, so a yeasty taste and cloudy appearance is appropriate.
If I was brewing an IPA with a high starting gravity, and I wanted to highlight the hoppy flavor of the beer, I would certainly conduct a secondary fermentation to remove as much yeast and yeast flavor from the finished beer to help both with taste and clarity. Depending on the beer style, gravity, fermentation temperatures, yeast strain, and yeast health, a secondary fermentation can typically last anywhere from two weeks to several months. When conducting a secondary fermentation on certain beers, such as sours, the secondary fermentation can in some cases last over a year.
An imperial chocolate stout being racked into a secondary fermentation carboy,
Beer being racked into a secondary fermenter.
Pitching or yeast pitching is the term used for when a brewer adds yeast to the cooled wort to begin the fermentation process. Yeast should be pitched to the wort as quickly as possible to diminish the possibility of wild yeast strains or bacteria taking control of the sweet wort before your selected yeast has the opportunity to. Additionally, your pitched yeast should be as close to the same temperature as the wort that you are adding it to in order to avoid shocking the yeast and to help the yeast acclimate as quickly as possible and lower yeast lag time. It is critical that your wort is in an appropriate temperature range for the yeast to be able to survive and thrive; for most ales that temperature range is between 65° and 80° F for pitching, but you should always consult your yeast’s packing for the specific temperature range of the variety you are using.
Cooled wort being aerated, just prior to having the yeast pitched.
Yeast pitching and aeration just prior to fermentation.
Primary fermentation in beer brewing is the initial fermentation process where yeast will convert most or all of the wort sugars to alcohol and CO2 (carbon dioxide). After the yeast has been pitched into the wort, there is typically between 2 and 24 hour yeast lag time where the yeast acclimates to the fermentation environment and begins to replicate consuming sugars and the available oxygen in the wort; there is little alcohol conversion and CO2 generated during the lag phase.
Once the lag phase completes, a foamy head called a krausen begins to form in the fermentation vessel. The krausen is composed mostly of proteins, yeast, and the carbon dioxide that the yeast is rapidly producing. During primary fermentation the yeast is producing approximately equal parts of both alcohol and CO2. Depending on the style of beer, original gravity, quantity of yeast pitched, and fermentation temperature, the primary fermentation for an ale will last between 5-14 days, then it will then be transferred to a secondary fermentation vessel to allow the beer to condition and finish out its fermentation. In some cases only a primary fermentation is completed, and the beer may spending additional time in the primary fermenter or condition in the bottle, keg, or holding vessel.
Primary fermentation occurring two days after the yeast was pitched into an American Wheat style Hefeweizen. The krausen has formed and a great deal of alcohol and CO2 is being produced.
Priming a beer is the process of adding sugar during the bottling process in order to carbonate the beer. You can bottle condition and carbonate your beer by priming it at the time of bottling with a specific amount of sugar. Using approximately .5 teaspoons ( ½ tsp) of priming sugar per 12oz bottle will provide adequate carbonation for most beer styles.
Typically you will want to prime your beer with corn sugar (dextrose). It is critical that your beer completes its fermentation prior to priming and bottling, as residual fermentable sugars can create excessive pressure in the bottles and cause them to explode. It is also critical that the yeast is still viable so that the priming sugar is converted to CO2 in the bottle, and you do not end up with a flat and overly sweet beer. As in all aspects of brewing, cleaning and sanitation is always paramount. Take special care to ensure that your bottles and caps are clean and sanitized prior to bottling.
Racking is the process of transferring beer from one brewing vessel to another. Beer is typically racked utilizing a racking arm, racking cane, or racking tube. The beer is either pumped from one vessel to another, or a siphon or CO2 tank is used to create a positive or negative pressure and gravity is used to rack the beer.
A wide selection of home brewing beer racking accessories can be found here:
Home Brewing Beer Racking Equipment
Beer being racked from a primary fermenter to a secondary fermenter using a racking cane and tube:
Beer being racked from a primary fermenter to a secondary fermenter.
The Reinheitsgebot, also known as the German Beer Purity Law, was originally drafted in 1487 and put into law on April 23rd, 1516 in the city of Ingolstadt, in Bavaria, Germany. The original Reinheitsgebot document stated that the only ingredients that could be used in the production of Bavarian beer were water, barley, and hops. In addition to ingredient restrictions, the document also set pricing standards for the sale of beer. At the time the Reinheitsgebot was drafted, the function of yeast in brewing was not understood, and for that reason it was not listed as an acceptable ingredient in beer.