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Brewing Coffee PDF Print E-mail
Written by c0ff33   
May 28, 2011 at 01:34 AM

3.1 Proper extraction times As a general rule, extraction time is directly proportional to grind coarseness. That is, the smaller the coffee particles, the shorter the extraction time should be. French press coffee generally has the longest extraction times, with coffee/water contact lasting as long as four minutes; the grind is, therefore, about the coarsest used. For those who prefer using a somewhat finer grind for this brewing method, the steeping period should be shortened. Espresso has the shortest contact time, about twenty-five seconds, so the particle size is among the smallest. Most of the desirable flavors—and the caffeine—are extracted first. If the coffee is allowed to remain in contact with the water for too long for its particle size, additional compounds start to extract and these will make the coffee taste bitter. Similarly, if your particle size is disproportionately large for your extraction time, only a small quantity of the desirable compounds will be extracted, so the coffee will be underextracted and lacking in flavor (which is not the same as weak).

3.2 A note on filtration versus percolation William Ukers' treatise "All About Coffee" notes that "true" percolation refers to dripping through "fine interstices of china or metal," while in filtration the dripping occurs through a porous substance such as paper or cloth. As a result, much of the current nomenclature is technically incorrect. However, the popular conceptualization of "percolation" now refers to a particular brewing device that may use either metal or paper filters; see section 3.9. Similarly, many drip devices use metal filters.

3.3 Drip Most of the coffee consumed in the United States is produced via some variant of the drip method: hot water is poured over medium-grind coffee contained within a filter; the water steeps and drips through, yielding coffee. The only impediment to the water's passage is resistance from the ground coffee and the filter. There are many variations on drip brewers' appearance and specific functionality; this FAQ will describe the more common ones. 3.3.1 Chemex® brewers Invented in 1941, the Chemex® brewer resemble an hourglass and has a distinct "science lab" appearance—not surprising, considering that it was invented by a chemist, Dr. Peter J. Schlumbohm, who combined a heavily modified glass funnel and an Erlenmeyer flask. Special paper filters are placed in the upper section; these filters, different than standard paper filters, are quite thick and manage to trap sediment while passing a large portion of the aromatic compounds. The filter is filled with medium- to coarse-grind coffee, a small amount of the brewing water is poured over the grounds, just enough to wet them, then the rest of the hot water is poured. If the filter cannot hold all of the brewing water, stop pouring until the level drops (as the brewed coffee drips out), then continue to add the water. Due to the thickness of the filters, you may find that a grind suitable for a standard paper filter is too fine for a Chemex® filter. Chemex® is a trademarked term, and therefore does not refer to a generic style of brewer. 3.3.2 One-cup brewers These are exactly that: they are small enough to fit onto a coffee mug, and brew one cup of coffee at a time. Some come with inserts that fit on top of and into the filter; these inserts have small perforations on their bottoms, and serve to regulate the flow of water dripping onto the coffee. These brewers often use metal filters, integrated into the unit as a whole. A few of these devices are made out of ceramic, while others are plastic; they esemble the filter basket section of auto-drip machines. Distinguish from 3.3.3 filtercone holders. 3.3.3 Filtercone holders Similar to the one-cup brewers, but they make larger quantities, dispensing the coffee directly into thermally insulated containers. These generally accept cone-shaped paper filters or similarly shaped metal mesh ones. 3.3.4 Vietnamese coffee maker This is basically a one-cup brewer, but there are some differences. The device has three parts: the main body looks like a small coffee cup and saucer molded together, with a threaded rod standing vertically in the middle of the inside; the bottom of the "cup" is a filter. A second filter fits into the main body; it has a hollow central post that screws onto the threaded rod. The last item is a lid. The cup or mug (onto which the coffee maker is placed) should first be heated by filling it with boiling water for a short while, then draining it. Place the main body onto the mug, fill it with finely ground coffee, and then screw the second filter down tightly. A coffee/chicory blend is traditional, as is pouring some sweetened condensed milk directly into the mug (though the milk can be added later). Pour a splash of very hot water into the brewer; the device should be filled up no more than a quarter of the way, as the ground coffee will soak up the water and expand. After about a half-minute, unscrew the second filter a couple of turns, fill the device with hot water and cover. It will take quite a long time to drain, perhaps five minutes. 3.3.5 Reversible coffee pot / flip pots / Napoletana These are comprised of four parts. One part looks like a very small pot with tall sides, a second like watering can with a large top opening; each of these parts usually has a handle. These two parts snap together, the open sides facing each other. Inside these pieces is a two-piece assembly that looks like a saltshaker. When the internal assembly is removed and its perforated lid unscrewed, a second perforated surface can be seen inside the "saltshaker," about one inch from the lip. Ground coffee is placed inside and the top screwed on; water is placed inside the pot-shaped piece, and all of the pieces are assembled. The side with the water is placed on a hot stove. When it is hot enough, water will begin to seep out of a tiny hole near the lip of the bottom piece. At this point, you flip the pot over, and the hot water will seep through the coffee into the piece with the spout. When this finishes, the top and middle portions are removed and the coffee is served. Most flip pots also come with a fifth piece: a lid that fits onto the serving unit after the coffee has been brewed. Note that the water seeping through the hole may well mean that it is boiling, so try timing things so that you flip the pot before the water boils. The Napoletana is not the only flip pot (reversible pot) that has been made, but it is the only one the average consumer will likely find these days. 3.3.6 Auto-drip The most common variant of the drip method is auto-drip; their greatest advantage is that they simplify the brewing process. Water is heated in one chamber and then piped over grounds contained in a filter; the brewed coffee then drips down into a serving carafe. These automatic machines have two prime faults: one, except for a few high-end brands, they do not make the water hot enough, so extraction occurs at sub-optimal temperatures. Secondly, the manufacturers proudly tout the machines' warming plates for keeping the coffee hot. However, continued application of heat will cause the coffee to turn bitter; a better choice is to either buy a machine with an integrated insulated carafe, or pour the coffee into a separate insulated carafe once the brewing cycle is complete. With careful research, you can find an auto-drip machine that does in fact reach proper brewing temperatures, the overall convenience arguably makes such a machine the best choice for most people. Other things to look for: good water dispersal (using a showerhead design to spread hot water over the grounds, rather than a single small spout), automatic shutoff for the warming plate (though you shouldn't use a warming plate, it's nice to have it shut off automatically if you forget about it). For autodrip machines, you have a choice between paper and metal mesh filters; the latter requires a slightly coarser grind.

3.4 Single-Serve Coffee Systems Once confined to commercial establishments, these devices have started to make their way into homes. They are very convenient: the coffee is pre-packaged in variously shaped containers (depending upon the machine) which are inserted into the machine, a button is pushed, and coffee comes out. The main variation here is whether the machine pre-heats an entire resevoir (lengthening the initial wait but shortening the time it then takes to brew multiple cups) or heats water on-demand (shortening the initial wait but brewing consecutive cups more slowly). Some machines have an option to brew with less water, making a stronger cup. These machines are generally akin to drip machines; although some pressure is often involved (sometimes creating a faux-crema), they are not true espresso machines since they do not achieve nearly the requisite pressure. Overall, the machines appear to be well-designed and they perform well. The weak point is the coffee itself. Since the machines use proprietary packaging, you are forced to use the manufacturer's coffee—similar in effect to inkjet printers and their cartridges. Since the coffee has been ground and packaged months in advance, you must rely on package technology to keep the coffee from staling. As a result, products reviews have found the quality of the brewed coffee to be spotty, and the most important issue not to be the machine itself, but the prepackaged coffee that can be used with it. While the packages' freshness may not favorably compare to freshly roasted and ground coffee, they will likely equal or exceed that of ground, canned coffee. Some coffeemaker brands support a broader range of coffee options than others. And, as with inkjet cartridges, you can often use "compatible" packages, though the manufacturers obviously do not encourage this and will not repair under warranty if a third-party product causes damage. There is an "unofficial" reusable adapter for one of the pod machines, the Philips Senseo, which seems to improve brew quality, albeit at the expense of convenience that is the machine's primary selling point.

3.5 Biggin The Oxford English Dictionary claims that this device was named after a "Mr. Biggin," though some sources surmise that the name came from the Dutch "beggelin", meaning to trickle. The first and perhaps original version was little more than a cloth bag that fit into a container, the bag's opening was held in place at the top by a metal ring. Other variants were quite elaborate; in one, a metal plate was used in conjunction with a screw device. When the top of the screw was turned, the plate would rise, compressing the bag. Another variant did away with the bag altogether, and the coffee was kept contained in metal cylinder with a perforated metal disk bottom. The screw would cause the disk to rise up in the cylinder, pulling the ground coffee out of the brewed coffee. Confusingly, certain French coffeemakers are labeled as Biggins. These devices are essentially drip pots, whereas to be labeled a Biggin, the device must operate by the steeping method: holding the coffee and water together, then isolating the spent grounds after the period concludes.

3.6 French Press / Press Pot / Cafetiere / Plunger Pot A French press consists of two parts: a beaker-shaped container made out of glass, metal, or plastic, and a plunger, which is a multi-piece wire-mesh filter assembly attached perpendicularly to a metal rod. Other filters may also ship with the press or be retrofitted onto them, such as finer mesh one-piece units, or nylon mesh screens to be used in conjunction with the standard filter; these serve to better remove fine sediment. Some presses are insulated; these work well for keeping the coffee hot during the steeping process. However, contrary to the manufacturers' instructions, you should pour off the coffee when it is ready and not keep in in the brewing vessel, else it will continue to steep and become bitter and over-extracted. To use a press, warm the carafe (beaker) by filling it with hot water and allowing it to sit for a minute or so while your brew water heats; the filter assembly should also be warmed by placing it into the water heating the carafe. This warming stage is optional, but will improve coffee quality, especially when brewing lesser amounts (heat absorption by the device will lower extraction temperature). Heat the brewing water as per the section on water temperature. Empty the carafe and put in the ground coffee. Common practice is to use a grind somewhat between that of auto-drip and percolator, but some people prefer to use a medium grind (similar to auto-drip) with a proportionately shorter steeping time (see below). Pour in the water and put the plunger in place but do not press it down yet; the lid, which is also part of the plunger assembly, will thereby reduce heat loss. Let it steep for about four minutes, a minute or two less if using a finer grind. In order to ensure thorough saturation, some people prefer to either stir the grounds about thirty seconds to a minute after adding the water, or, and perhaps better, add about a third of the water, wait about twenty or thirty seconds, then add the rest. If using a glass carafe, do not stir the grounds with a metal implement, as this may damage the carafe. When the time is up, push down the plunger to trap the grounds at the bottom, and pour off the coffee. If the plunger resists being pushed down, do not force it (there is anecdotal evidence that excessive pressure could cause the glass to shatter); back the plunger up and try again. If you have repeated problems pushing the plunger down, you have either ground the beans too finely, or your grinder produces excessive dust, which is choking the filter. Note that this brewing method leaves all of the coffee oils in the coffee. This will create a rich, tasty cup, but there is some medical evidence that these oils may have adverse medical effects. Some people dislike the sediment that almost inevitably occurs when using the press. Though not a fatal flaw, one issue that plagues French presses is heat loss. Pre-warming the carafe (and filter assembly) will reduce this problem, but the glass is quite thin, so the temperature of the water may drop below optimal brewing temperatures while steeping. Insulated presses will virtually eliminate heat loss; however, such presses now in production are made of either plastic or metal (stainless steel), and some users claim that this material lends an off-flavor to the coffee. Insulated fabric covers for presses, similar to tea cozies, are also available In the United States, "French press" is the most commonly used appellation, whereas cafetiere is used in parts of Europe; however, cafetiere literally means "coffeemaker," so some confusion could arise if this term is used. The term plunger pot may have negative connotations, since in the US a plunger is also a device used to open clogged plumbing. As an interesting side note: a press can be a good indicator of a coffee's freshness. When the hot water is added, very fresh coffee will foam up significantly, and stale coffee, not at all. Like the biggin, this process is known as steeping.

3.7 Espresso Espresso is a beverage created by forcing water at proper brewing temperatures through finely ground coffee at approximately 9 atmospheres of pressure; contrary to how it is often incorrectly described, steam does not contact the grounds. The resultant brew is quite different than coffee. While coffee is essentially a solution, espresso is at once a solution, a suspension of solids, and an emulsion. A proper espresso is capped with light-brown crema, which David Schomer, owner of Espresso Vivace, notes has been described as a "polyphasic colloidal foam." This topic is outside the scope of this document; see the Original espresso FAQ or this one.

3.8 Vacuum pot Dating back to at least the 1830s, these devices were quite common in the 1930s through the 1950s. Though more complex forms exist, the basic principle remains the same for all of them. A lower container resembling an auto-drip machine's carafe is filled with water (hereafter, the lower bowl will be referred to as the carafe). An upper bowl, basically funnel-shaped, is put on top of the carafe, forming a seal; the funnel's tube leading down into the carafe nearly to the bottom. The top of the tube is covered by one of various designs of filters. Somewhat finely ground coffee is placed into this top bowl, then the carafe is placed onto a heat source. This can be a stovetop flame, an alcohol or butane lamp, or an electric element; if an electric stove is used, a wire trivet must be placed between the element and the carafe's bottom.If an alcohol lamp is used, it is best to pre-heat the water, due to relatively low amount of heat produced by the lamp. As the unit is heated, the increased air pressure in the otherwise sealed carafe forces the water up the tube into the top bowl, where it mixes with the ground coffee. This is not caused by steam pressure; that would indicate that the water was overheated. What might appear to be steam is simply the hot air from the lower bowl, which has followed the water it pushed up and is now bubbling vigorously through the brewing coffee in the upper bowl. When most of the water has moved to the top portion, the heat is reduced and the mixture is allowed to steep for a minute or so. The device is removed from the heat source. As the lower bowl cools its internal pressure drops precipitously, pulling the liquid down from the upper chamber--often accompanied by a loud gurgling. The heating container now doubles as the serving carafe. Because of the filter, the grounds remain behind in the top container. This process produces an excellent cup of coffee, and is certainly quite fun to watch. While most vac pot filters are made from cloth or plastic mesh, the now-discontinued Cory pots used a glass rod that fits into the top of the tube leading down to the lower bowl (the rod can also be found with some Silex pots). While effectively removing sediment, it also allows the coffee oils to remain in the brewed coffee. Cona currently makes a version for their vac pots, and many users feel the newer version of the rod works better than the older models. Brands and places of manufacture: current manufacturers include Cona in England, Hario in Japan, Yama Glass in Taiwan, and Bodum in Denmark. Bodum currently also makes two electric models, small and large, that simplify the process. Black and Decker recently introduced a model; due to what may have been poor promotion, it was soon taken off of the market. Cory and Silex (Proctor-Silex) used to make them in the U.S.; Sunbeam once made a metal model with a built-in heating element. See here for more information. One particularly interesting model is the balancing siphon coffee maker, the only current example of which is made by coffee4you.com. Dating back to models pioneered in the 1840s, the principle is basically the same as the above versions, but the two chambers (water and coffee) are positioned side-by-side on a balance beam. The weight of the water in the heating chamber causes that side of the balance to drop while the side with the coffee grounds chamber stays up in the air. A lamp is lit under the water chamber (to which hot water was added), and the soon near-boiling water is sucked over to the coffee chamber. Since the weight is transferred to the other side, the water chamber is lifted off of the lamp, which is automatically extinguished, causing the water chamber to eventually cool and suck the finished coffee back where it is dispensed via spigot. This brewing method is closest to steeping, with the added twist of the pressure changes used to move the water.

3.9 Percolator Originally a referent for a broader series of coffee makers (see section 3.2), the term percolator now generally refers to a specific sort of device. As defined in the United States, percolators consist of a chamber that holds the water, into which a long tube with a filter basket at the top end is placed. The filter basket is generally made of perforated metal, but many models accept paper filters. Coarsely ground coffee is placed into the filter and the water is heated, either by in integrated electric element or a stovetop burner. When the water boils, it is drawn up the tube and repeatedly passed over the grounds. That is, the brewed coffee drips back down into the hot water, and that coffee/water mix is then passed back over the grounds, over and over again. Many people become sentimental when they think about percolators, often recalling childhood memories and the smell of coffee in the air in the morning. Nostalgia aside, percolators are by far the least well-regarded of brewing methods. The water is overheated, the brew overextracted (only water should be spread over coffee grounds, not already-brewed coffee), and the percolating action dissipates the complex, volatile compounds into the atmosphere. This is why people often recall that wonderful aromas: the aromatics that should be in the coffee are instead cast off into the atmosphere.

3.10 Ibrik / cezve / briki / mbriki "Ibrik" and "cezve" are Turkish; "briki" and "mbiki" are Greek, though the difference is largely semantic. There may well be no definitive way to prepare this product, as there are significant regional variations in traditional preparation; several alternate brewing techniques will be noted. First, fill the ibrik approximately two-thirds full with clean, cool water (if desired, sugar can also be added at this point) and heat until hot but not yet simmering, then add very finely powdered coffee. Some customs have you add the coffee before heating. The coffee should be evenly distributed on top of the water so as to block the opening. Use approximately one tablespoon per three ounces of water; more coffee should be added if a seal is not formed. The quantity of powdered coffee is very flexible, with some people insisting that they grew up using one teaspoon per three ounces, others saying a tablespoon or even more. Regardless, a quantity sufficient to seal off the neck of the ibrik is necessary. Differing opinions regarding coffee quantity may reflect a misrecollection of the container size. The water should come nearly to a boil in a minute or two and begin to foam up through the coffee. If your coffee boils rather than foams, you may have used too little coffee or over-heated the water. When this foam rises somewhat thickly, remove the pot from the heat long enough for the foam to settle. One tradition has you immediately pour the coffee into a demitasse, making sure to cover the top with foam (and therefore not wait for it to settle before you pour). Another tradition is to repeat this foaming process one or two times with a low heat setting. The grounds should settle in the cup before drinking. Another tradition has you wait until the grounds settle in the ibrik itself, but this runs the risk of losing the foam before pouring. If you use the latter technique, you may wish to preserve the foam by scooping some into the cups before waiting for the grounds to settle. One common tradition is to mix powdered cardamom with the coffee before heating. This brewing method is known as "decoction." Grinders tend to have trouble making the powder fine enough. Turkish coffee grinders, resembling pepper grinders, are available. Many feel that the lowly whirly blade grinders work adequately, but they may overheat the coffee during the long grinding process: Turkish grind is even finer than espresso grind, almost the consistency of talcum powder. A note on boiling: it is unclear whether the water actually comes to a boil with this process, or whether the foaming is merely an effect that appears to mimic the visual appearance of boiling.

3.11 Moka pot The moka pot is sometimes misleadingly referred to as a stovetop espresso maker. There are many variations in design for this device, but the basic function is the same. At its most basic, the moka pot consists of 3 parts: 1) a chamber at the bottom for the water. It has a threaded opening for the top (not middle) section, and a pressure relief valve. This section is almost invariably made from metal. Before using, it is filled with water to just below the relief valve; do not fill completely. 2) the middle part holds the ground coffee. It is a metal ring with a funnel attached to its bottom (all one piece); the funnel is separated from the ring by a screen, which usually spreads across the bottom of the ring before it narrows for the funnel. This component is also made of metal. This section simply drops into the lower section, and finely ground coffee is spooned in until full or slightly heaping. The grounds are not tamped. 3) The brewed coffee flows into and is poured from the top section, which has a threaded opening for the bottom section and is topped off by a lid, commonly one that flips open and closed. This component varies the most, both in shape and composition; there are also models where this section is made from clear, heat-resistant plastic, emabling the user to see the brewing coffee flowing in. The bottom of this section has a screen very similar to the one in the middle section. This screen also leads to a tube, one that points up into the upper section. The upper section gets threaded onto the bottom section, thereby slightly packing the coffee in the middle section. The assembled device is placed on the stove and the water is heated. Since the lower chamber is airtight (the funnel bottom is situated below the waterline), the expanding air pushes down on the the water and forces it up the lower tube, through the coffee and through the top tube. It spurts out of the tube (which ends near the top of the upper chamber) and drops down into the bottom of the top reservoir. The brewed coffee is them poured off. This is similar to how a vacuum pot works, except that (1) rather than mixing with the coffee and steeping, the water is forced under some pressure though the coffee, and (2) the brewed coffee remains in the top portion. A moka pot can make good quality, strong coffee. Notes: 1. Start with a somewhat coarser grind than used for drip. The trick is to allow a small amount of resistance to the water flow without creating a clog. Similarly, the coffee should not be packed, as the grounds will expand when they become wet and may otherwise clog the device. Too fine a grind may also choke the moka pot and possibly pop open the safety (pressure-relief) valve. On the other hand, if the coffee holder is not filled sufficiently, water (seeking the path of least resistance) may seek relatively empty "channels" in the coffee, thereby creating a weak brew. Make sure that there are no grounds on the lips of either the lower or middle sections, as this may prevent a tight seal. 2 . Stoves can vary; you want the water to heat in about five minutes, so a low to medium heat setting should be fine. Do not use a very high heat. Get to know your stove. 3. When the device makes a gurgling sound, remove it from the heat and it will finish brewing on its own. Do not be concerned if there is some water left in the bottom section; you would have to overheat the unit to get the last bit out. 4. It is crucial to have airspace in the bottom section; the pressure relief valve must be kept unblocked in case of a clog, to prevent the lower chamber from bursting, and the airspace is needed to help create the pressure used to push the water up. The moka pots most commonly sold in the United States are made out of aluminum. Although there are no definitive links between aluminum and adverse health effects, (see, Scientific American: Is there any proof that Alzheimer's disease is related to exposure to aluminum--for instance, by using aluminum frying pans? many people insist that aluminum imparts a metallic taste, and will thus only use a stainless steel model. Some varieties have built-in wands that dispense the brew and/or can generate steam for steaming and milk.There is at least one electric moka pot. As already noted, moka pots are sometimes referred to as stovetop espresso machines. However, these devices cannot achieve the pressure required to achieve the emulsion of oils and colloids unique to espresso; moka pots make strong coffee, but not espresso.

3.12 Cold water process This promises to make a brew that is better tolerated by people who find that coffee upsets their stomachs. Basically, add one pound to about nine cups of cold water and store at room temperature overnight (about twelve hours). Filter and refrigerate; although refrigeration is not crucial, it will extend the usable shelf life. This makes a concentrate that is not directly drinkable. To serve, add one ounce of the concentrate to six ounces of very hot water. All of these proportions can be adjusted: use more or less water for steeping, and/or adjust dilution ratios. This coffee will be smoother and easier to drink, but it will lack the highlights and subtleties of hot-brewed coffee, since certain compounds are only extracted at the higher temperature; many will find the taste lacking. There are two brands of commercial cold water process coffee makers, by Toddy Products® and Filtron®, that simplify steeping and, most especially, filtering. Alternatively, you can simply use a French press for the whole process.

3.13 Microwave brewing Distinguishable from simply heating the water in a microwave, there are various devices sold for brewing coffee in a microwave oven. These devices take various forms, but following are two examples. One device works basically like a moka pot, but made out of plastic in order to be usable in the microwave. Another design has you combine the water and ground coffee in a chamber. When the water/coffee mixture hits a certain temperature, a bimetallic strip at the bottom bends, and the coffee drips down through a filter into a lower chamber or mug. Reviews of these products have not been positive.

3.14 Instant This is partially a preparation method, and partially a form of coffee. Instant coffee is brewed coffee that has had the water removed by some form of evaporation. First, coffee is brewed in large quantities, usually at a higher extraction rate than is normally used; a evaporative process is then used to concentrate the brew. Next, a powder is produced by one of two methods: (1) spray drying, where very fine streams of the brew are blown into hot, dry air, evaporating the water, or (2) freeze drying, where the liquid is first frozen, then placed in a vacuum, which vaporize the water through sublimation. The spray drying method is especially prone to loss of coffee essences, whish are partially captured during evaporation and added back to the powder. Various agents are often added to color the resultant powder and cause it to clump together, in order to make it resemble ground coffee. A shot of aroma is added to give the powder a desirable smell when the container is opened; however, this is deceptive, as the aroma is not inherent in the powder and will not be reflected in the brewed cup. Instant coffees often contain a very large percentage of robusta beans. Instant is the least desirable method of preparing coffee.

3.15 Filters There are five types of filters: paper, metal, plastic, cloth, and glass. 3.15.1 Paper filters Paper filters are the most commonly encountered variety. They do the most thorough job in removing particulates, but will also absorb some of the essential oils and aromatics from the coffee. This will yield a brew with less aroma and perceived body; Chemex brand filters purport to allow the aromatic compound through. Filters are akin to copy paper in that their thicknesses can vary from brand to brand, as can their constituent fibers; as a result, their impact upon the brew's flavor will differ. These filters are disposable, with the concomitant factors of easier cleanup and increased waste and resource usage. Paper filters may also be divided into bleached and natural varieties. The natural filters can impart a taste described as wet cardboard, especially if a lower-quality brand is used. Though once bleached with chlorine, most bleached filters are now whitened with oxygen. Avoid cheap filters; in addition to possibly effecting the coffee's taste, they may clog easily, either overextracting or forcing you to use a coarser grind and thereby possibly underextracting. Paper filters are most often used with most types of drip coffee makers and with percolators. 3.15.2 Metal filters There are two quite different sorts of perforated metal filters. One sort uses relatively large holes to filter the coffee. They will allow all of the oils and aromatics through, but will also pass fine particulates into the brewed coffee. These filters are usually integrated into moka pots, Neapolitan flip pots, as well as many percolators. The other kind is the permanent metal filters sold for drip brewers (mainly auto-drip) in which the perforations, in the form of miniscule slits, are much, much finer. Most are either stainless steel or gold-plated in order to prevent off-tastes from being imparted to the coffee. They trap quite a lot of the particulates while passing the oils and aromatics, but the brew won't be quite as "clean" as with paper filters. A different type of metal filters are the woven wire mesh filters, similar to the material used for window or door screens, but the mesh is considerably finer. Again, no coffee oils or aromatics are absorbed, but a quantity of particulates may be passed through. These filters are typically used with French presses and some autodrip machines. 3.15.3 Cloth filters Cloth filters are rarely used these days, and were once used with many varieties of vacuum pots. Their absorption is similar to that of paper filters, but they can be rinsed and re-used many times. They should be very well cleaned periodically, or they may transmit off-flavors to the coffee. Cloth holders, sometimes literally socks, have been used for steeping ground coffee in hot water, and have been used in devices such as the Biggin. 3.15.4 Plastic filters These are sometimes sold with less-expensive drip machines. They do not trap oils and aromatics, and will pass sediment. Many feel that they impart an undesirable taste to the coffee, and they do not last very long. Nylon mesh filters are also sold for French presses, either for use on their own or in conjunction with the metal mesh filters. These do not seem to cause off-tastes, and will trap more sediment than the mesh filters. Some vacuum pots also use these nylon filters. 3.15.5 Glass filters These work with many styles of vacuum pots and resemble a short glass wand; they fit into the downspout of the vacuum pot's upper bowl. They are surprisingly effective at keeping out particulates, especially the Cona models.

3.16 A final note on brewing techniques The categorizations above are, to some degree, a simplification. Valid arguments may be proffered that the divisions are not so clear, that some brewing devices in one category are also akin to devices in a different one.

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Last Updated ( Feb 20, 2013 at 03:53 PM )

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