question: Why do coffee brewers reccomend cold, purified water when it's just going to make the water hot and filtered through the beans anyway?
comment: Well for one, hot water generally comes from hot water tanks. Try running a hot tap for a bit, filling a glass, cooling it, and comparing the taste of the formerly hot water to the taste of water that came from the cold tap. It's going to look and taste a bit funky. Why? When you put a bunch of water in a tank for a long time, gradually minerals are going to build up in the tank. Throw a bunch of water in that tank again, and it's going to have a different mineral composition than what's coming straight through the cold taps to the faucet from the municipal water supply/well/etc. Purified water? Same deal. More consistent mineral makeup. Different cities/wells have very different water quality and makeup so if you want to suggest something to someone that will consistently make good coffee, you suggest something consistent - that being, water that's had all that extra stuff removed. Is this something you NEED to do? Probably not. Does it help? Sometimes.
passages: Brewed coffee is made by pouring hot water onto ground coffee beans, then allowing to brew. There are several methods for doing this, including using a filter, a percolator, and a French press. Terms used for the resulting coffee often reflect the method used, such as drip brewed coffee, filtered coffee, pour-over coffee, immersion brewed coffee, or simply coffee. Water seeps through the ground coffee, absorbing its constituent chemical compounds, and then passes through a filter. The used coffee grounds are retained in the filter, while the brewed coffee is collected in a vessel such as a carafe or pot.
   Coffee percolators once enjoyed great popularity but were supplanted in the early 1970s by automatic drip coffee makers. Percolators often expose the grounds to higher temperatures than other brewing methods, and may recirculate already brewed coffee through the beans. As a result, coffee brewed with a percolator is particularly susceptible to over-extraction. Percolation may remove some of the volatile compounds in the beans, resulting in a pleasant aroma during brewing, but a less flavoursome cup. However, percolator enthusiasts maintain that the potential pitfalls of this brewing method can be eliminated by careful control of the brewing process.
  
  Section::::Brewing process.
   Coffee percolators and automatic coffeemakers brew coffee using gravity. In an automatic coffeemaker, hot water drips onto coffee grounds that are held in a paper, plastic, or perforated metal coffee filter, allowing the water to seep through the ground coffee while extracting its oils and essences. The liquid drips through the coffee and the filter into a carafe or pot, and the spent grounds are retained in the filter.
   Because the coffee grounds remain in direct contact with the brewing water and the grounds are filtered from the water via a mesh instead of a paper filter, coffee brewed with the cafetiere captures more of the coffee's flavour and essential oils, which would become trapped in a traditional drip brew machine's paper filters. As with drip-brewed coffee, cafetiere coffee can be brewed to any strength by adjusting the amount of ground coffee which is brewed. If the used grounds remain in the drink after brewing, French pressed coffee left to stand can become "bitter", though this is an effect that many users of cafetiere consider beneficial. For a cafetiere, the contents are considered spoiled, by some reports, after around 20 minutes. Other approaches consider a brew period that may extend to hours as a method of superior production.
   Filter drip brewing (invented 1908, Melitta Bentz) uses a bed of coffee grounds placed in a holder with a filter to prevent passage of the grounds into the filtrate and hot water is passed through the grounds by gravity. This is distinct from percolator brewing due to the fact that the water is not recycled through the grounds, and the water does not have to be boiled to reach the brew chamber. (In many automatic drip machines, the water is boiled or nearly boiled to raise it through a tube to the brewing chamber, but this is an implementation detail specific to those machines, and not required by the process, which was first used manually.)
   In addition to the "cold press", there is a method called "Cold Drip Coffee". Also known as "Dutch Ice Coffee" (and very popular in Japan), instead of steeping, this method very slowly drips cold water into the grounds, which then very slowly pass through a filter. Unlike the cold press (which functions similar to a French Press) which takes eight to twenty-four hours, a Cold Drip process only takes about two hours, with taste and consistency results similar to that of a cold press.
  
  Section::::Brewing.:Pressure.
   Drip-brewed, or filtered, coffee is brewed by hot water passing slowly over roasted, ground coffee beans contained in a filter. Water seeps through the ground coffee, absorbing its oils, flavours and essences, solely under gravity, then passes through the bottom of the filter. The used coffee grounds are retained in the filter with the liquid falling (dripping) into a collecting vessel such as a carafe or pot. Paper coffee filters were invented in Germany by Melitta Bentz in 1908. To reduce waste, some coffee drinkers use fine wire mesh filters, which can be re-used for years. Many countries in Latin America and Africa traditionally prepare drip coffee using a small reusable bag made of cotton or other cloth.
   A distinction must be made between the chemical process of percolation and the coffee percolator as a device. In 1880, Hanson Goodrich invented the coffee percolator. His percolator was one of the earliest coffee brewing devices to use percolation rather than infusion or decoction as its mode of extraction, and he named it accordingly. Other brewing methods based on percolation followed, and this early naming convention can cause confusion with other percolation methods.
   Filter coffee is central to Japanese coffee culture and connoisseurship. 
  
  Drip brewing is a widely used method of coffee brewing. There are several manual drip-brewing devices on the market, offering a little more control over brewing parameters than automatic machines, and which incorporate stopper valves and other innovations that offer greater control over steeping time and the proportion of coffee to water. There also exist small, portable, single-serving drip brew makers that only hold the filter and rest on top of a mug or cup. Hot water is poured in and drips directly into the cup. 
   Cold brewing, also called "cold water extraction" or "cold pressing," is the process of steeping coffee grounds in water at cool temperatures for an extended period. Coarse-ground beans are soaked in water for a prolonged period of time, for 12 to 24 hours.
   In order to reduce the contamination generated by the wet process of coffee fruits, scientists at Cenicafé developed a technology that avoids using water when not needed and uses the right water when needed. The technology, called "Becolsub" (taken from the initials of the Spanish for ecological wet coffee process with by-products handling: "Beneficio Ecologicos Sub-productos"), controls more than 90% of the contamination generated by its predecessor. The quality of the coffee processed this way is the same as for coffee processed by natural fermentation.
   In the case of decaffeinated coffee, eliminating caffeine can cause a sharp decline in the natural taste of the coffee bean. During the process of decaffeination, the largest coffee producers in the world use a variety of ways to remove caffeine from coffee, often by means of chemical manipulation and the use of potentially harmful chemical components, such as methylene chloride or ethyl acetate. One process that does not use solvents is the patented Swiss Water Process, which relies on soaking beans in a bath which is essentially brewed coffee from unroasted green beans. The caffeine permeates into the bath at a much higher rate than most of the flavor elements. While the process is certified organic, the water solubility of coffee flavor compounds assures that some of the coffee flavor is lost or changed by the bath. The process is more costly than solvent methods, and is performed commercially by only one plant in British Columbia, Canada. Therefore, only a small percentage of decaffeinated coffee available on the market uses this method.
   Another variation is cold brew coffee, sometimes known as "cold press." Cold water is poured over coffee grounds and allowed to steep for eight to twenty-four hours. The coffee is then filtered, usually through a very thick filter, removing all particles. This process produces a very strong concentrate which can be stored in a refrigerated, airtight container for up to eight weeks. The coffee can then be prepared for drinking by adding hot water to the concentrate at a water-to-concentrate ratio of approximately 3:1, but can be adjusted to the drinker's preference. The coffee prepared by this method is very low in acidity with a smooth taste, and is often preferred by those with sensitive stomachs. Others, however, feel this method strips coffee of its bold flavor and character. Thus, this method is not common, and there are few appliances designed for it.
   In France, in about 1710, the infusion brewing process was introduced. This involved submersing the ground coffee, usually enclosed in a linen bag, in hot water and letting it steep or "infuse" until the desired strength brew was achieved. Nevertheless, throughout the 19th and even the early 20th centuries, it was considered adequate to add ground coffee to hot water in a pot or pan, boil it until it smelled right, and pour the brew into a cup.
   Glazer and Marotta hired two former Westinghouse engineers, Edmund Abel and Erwin Schulze, to design a drip coffee machine for household use. Abel and Schultze designed a machine with filtered water, heated to 200 degrees Fahrenheit, through coffee grounds scooped into a paper coffee filter. The coffee is then dispensed into a glass carafe.
   Coffee may be brewed by steeping in a device such as a French press (also known as a cafetière, coffee press or coffee plunger). Ground coffee and hot water are combined in a cylindrical vessel and left to brew for a few minutes. A circular filter which fits tightly in the cylinder fixed to a plunger is then pushed down from the top to force the grounds to the bottom. The filter retains the grounds at the bottom as the coffee is poured from the container. Because the coffee grounds are in direct contact with the water, all the coffee oils remain in the liquid, making it a stronger beverage. This method of brewing leaves more sediment than in coffee made by an automatic coffee machine. Supporters of the French press method point out that the sediment issue can be minimized by using the right type of grinder: they claim that a rotary blade grinder cuts the coffee bean into a wide range of sizes, including a fine coffee dust that remains as sludge at the bottom of the cup, while a burr grinder uniformly grinds the beans into consistently-sized grinds, allowing the coffee to settle uniformly and be trapped by the press. Within the first minute of brewing 95% of the caffeine is released from the coffee bean.
   An increasingly popular preparation offered by coffee service providers is known as a "frac pac". This is ground coffee in a self-contained packet, enveloped by a filter. This allows a conventional drip coffee maker to be used, but without the mess of cleaning out the old grounds and without the requirement to measure out the right amount of coffee. The user only needs remove the old pack and to place the new pack into their coffee machine. 
   Water temperature is subtler but crucial to the proper extraction of flavor from the ground coffee, as it affects the proportions in which solubles are extracted – one wishes to extract the desired flavors as much as possible, and the undesirable flavors as little as possible. The recommended brewing temperature range of coffee is 91–94 °C (195–202 °F), which is a trade-off between these goals. If cooler, some of the solubles that make up the flavor will not be extracted. If the water is too hot, some undesirable, bitter, elements will be extracted, adversely affecting the taste. Note that this desired temperature range is slightly below the boiling point of water (100 °C or 212 °F at standard pressure), so coffee is best made with water that has been allowed to come off the boil slightly. Another consideration is the difference between the temperature of the water and the temperature of the coffee slurry: for example, certain brewing methods (e.g., manual pourover) can result in losing a significant amount of heat to the atmosphere during the brewing process.
   Because the ground coffee beans in cold-brewed coffee never come into contact with heated water, the process of leaching flavor from the beans produces a chemical profile different from conventional brewing methods. Coffee beans contain a number of constituent parts that are more soluble at higher temperatures, such as caffeine, oils and fatty acids. Brewing at a lower temperature results in lower acidity and lower caffeine content when brewed in equal volume. It is around 65 to 70 percent less acidic than hot drip coffee or espresso, per part. Although less caffeine is extracted with the cold brew method, a higher coffee-to-water ratio is often used, between 2 and 2 1/2 times. This may compensate for this difference in solubility, resulting in a brew with equal, if not more, caffeine (although this is unlikely).
   The water is normally kept at room temperature, but chilled water is also used. The grounds are filtered out of the water after they have been steeped using a paper coffee filter, a fine metal sieve, a French press, or felt, in the case of the "Toddy" brewing system. The result is a coffee concentrate that is diluted with water or milk, and is served hot, over ice, or blended with ice and other ingredients such as chocolate. 
   Recently, the Mr. Coffee product development team altered how their drip coffee maker works with a method dubbed "Optimal Brew". The coffee maker does not use the previously mentioned traditional method of routing the water over a heating coil under the warming plate invented by Marotta, Abel, and Schulze. Instead, a small flash boiling chamber flash heats the water to deliver the water to the beans within a temperature range of 195–200 °F. Heating the water this way allows 10 cups to be brewed in generally less than eight minutes, depending on the barometric pressure. Once brewed the coffee stays warm in a thermal carafe without requiring a heating plate which could potentially burn the coffee. This coffee maker, engineered and designed by TEAMS Design USA and the Jarden team, won a Red Star Award in 2010 and an Appliance Magazine EID Award in 2011.
   Extraction depends in subtle and complex ways on brewing method. Simplest is directly mixing the grounds and water, as in cupping, press pot, and vacuum brewing. Note that in Turkish coffee, the grounds are very finely ground and not removed from the water – this yields essentially 100% extraction of the solubles (over-extraction by Western standards), and suspension of the remaining insoluble parts of the grounds in the water. Significantly more complicated is brewing via soaking a column of grounds, as in filter, espresso, or percolation – in this case the water soaks and moves through the column of grounds, and (if there is water on top, as in espresso or percolation), a gradient develops over the column.
   When fermentation is complete, the beans are washed thoroughly to remove fermentation residues and any remaining mucilage. If not removed, these cause decolouring of the parchment and make the beans susceptible to yeasts. After washing, the beans are dried. When the drying process is not rapid enough earthy and musty taints, like "Rio-flavor" come up.
  
  Section::::Water usage.
   Throughout the latter part of the 20th century, a number of inventors patented various coffeemaker designs using an automated form of the drip brew method. Subsequent designs have featured changes in heating elements, spray head, and brew-basket design, as well as the addition of timers and clocks for automatic-start, water filtration, filter and carafe design, and even built-in coffee grinding mechanisms.
  
  Section::::Types.:Pourover, water displacement drip coffeemakers.
   The name is derived from the word "percolate" which means "to cause (a solvent) to pass through a permeable substance especially for extracting a soluble constituent". In the case of coffee-brewing the solvent is water, the permeable substance is the coffee grounds, and the soluble constituents are the chemical compounds that give coffee its color, taste, aroma, and stimulating properties.
  
raw_presuppositions: Cold purified water and hot water have the same properties.
raw_corrections: Cold purified water is more consistent while hot water has mineral buildup.