Drip coffee



Drip coffee is made by pouring hot water onto ground coffee beans, allowing it to brew while seeping through. There are several methods for doing this, including using a filter. Terms used for the resulting coffee often reflect the method used, such as drip-brewed coffee, or, somewhat inaccurately, filtered coffee in general. Manually brewed drip coffee is typically referred to as pour-over 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.

History
Commercial paper coffee filters were invented in Germany by Melitta Bentz in 1908 and are commonly used for drip brew all over the world. In 1944, Willy Brand developed an automatic drip-brewer utilizing circular paper filters in Switzerland. In 1954, one of the first electric drip brewers, the Wigomat invented by Gottlob Widmann, was patented in Germany. Drip brew coffee makers largely replaced the coffee percolator (a device combining boiling, drip-brewing and steeping) in the 1970s due to the percolator's tendency to over-extract coffee, thereby making it bitter. One benefit of paper filters is that the used grounds and the filter may be disposed together, without a need to clean the filter. Permanent filters are also common, made of thin perforated metal sheets, fine plastic mesh, porous ceramics or glazed porcelain sieves that restrain the grounds but allow the coffee to pass, thus eliminating the need to have to purchase separate filters which sometimes cannot be found in some parts of the world. These add to the maintenance of the machine but reduce overall cost and produce less waste.

Characteristics
Brewing with a paper filter produces clear, light-bodied coffee. While free of sediments, such coffee is lacking in some of coffee's oils and essences; they have been trapped in the paper filter. Metal, nylon or porcelain mesh filters do not normally remove these components.

It may be observed, especially when using a tall, narrow carafe, that the coffee at the bottom of the coffeepot is stronger than that at the top. This is because less flavor is available for extraction from the coffee grounds as the brewing process progresses. A mathematical argument has been made that delivering comparable strength in two cups of coffee is nearly achieved using a Thue–Morse sequence of pours. This analysis prompted a whimsical article in the popular press.

Cultural impact
Filter coffee is central to Japanese coffee culture and connoisseurship.

In South India, filter coffee brewed at home is known as Kaapi and is a part of local culture. Most houses have a stainless-steel coffee filter and most shops sell freshly roasted and ground coffee beans. Some popular filter coffee brands include Mysore café, Hill coffee (Suresh healthcare), Cothas Coffee (Bangalore) and Narasu's Coffee (Salem). It is common in South India and Louisiana to add chicory to coffee to give it a unique taste and flavour.

Methods
There are a number of methods and pieces of equipment for making drip-brewed coffee.

Manual pour-over coffee preparation
Pour-over methods are popular ways of making specialty drip coffee. The method involves pouring water over a bed of coffee (sometimes also called cake) in a filter-lined conical or cylindrical chamber typically consisting of a filter and a suitable filter holder. The filtering can be with paper, cloth, plastic, ceramics, or metal.

The quality of the resulting coffee is extremely dependent on the technique of the user, with pour-over brewing being a popular method used in the World Brewers Cup.

The pour-over coffee preparation method typically starts by pouring a small amount of hot water over the coffee grounds and allow it to sit for about half a minute before continuing the pouring. This pre-wetting, called blooming, will cause carbon dioxide to be released in bubbles or foam from the coffee grounds and helps to improve the taste.

There are several manual drip-brewing devices on the market, offering 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, making them a popular option for backcountry campers and hikers. Hot water is poured in and drips directly into the cup.

Different filter shapes and sizes exist, most notable the (paper) coffee filter systems introduced by Melitta (1908, 1932, 1936, 1965), Chemex (1941) and Hario (2004).

Cafetière du Belloy and similar coffee makers
Manual drip coffee makers include the so-called French drip coffee pot (invented in 1795 by François Antoine Henri Descroizilles and manufactured by a metal-smith in Rouen, then popularized by bishop Jean-Baptiste de Belloy  for why it became known as Cafetière du Belloy in Paris since 1800  to the point that it was sometimes incorrectly attributed to the bishop himself ), the Grègue (café grègue, café coulé, etc.) originating from La Réunion and also common in Louisiana, and the so-called Arndt'sche Caffee-Aufgussmaschine (Quedlinburg, Germany, c. 1900). French drip devices emerged from the earlier coffee biggins where cloth filters would be fully inserted into the pot for steeping instead of drip filtering. French drip coffee pots don't use paper filters but a permanent filter featuring many small round drilled holes made out of (enameled) metal, ceramics or porcelain. A cafetière du Belloy was originally made out of tin, later versions were made out of silver, copper, ceramics or porcelain. The Grègue and the Arndt'sche Caffee-Aufgussmaschine are built out of (enameled) metal. To avoid sediments in the coffee, coarsely ground coffee has to be used.

Around 1895, skyblue enameled metal coffee pots named Madam Blå were introduced in Denmark by Glud & Marstrand. They looked similar to French drip coffee pots, but used cotton filters and were available in 18 sizes for up to 50 cups of coffee.

The Drip-O-lator is an American coffee pot for making drip coffee patented in 1921 and in 1930 and manufactured in Massillon, Ohio, or Macon, Georgia, United States. The production of Drip-O-lators ceased in the middle of the twentieth century. The pots have become collectibles similar to bric-à-brac.

In the 1930s, the German company Melitta produced a series of manual coffee makers called Kaffeefiltriermaschine ("coffee filtering machine"). They worked on the principle of French drip coffee pots, but used a paper filter and allowed to pour the whole amount of water at once instead of having to pour several times.

Flip coffee pots
A less familiar form of drip brewing is the reversible or "flip" pot commonly known as Napoletana (1819) and late-19th century variants like the Russian reversible pot aka Russian egg, the reversible Potsdam cafetière aka Potsdam boiler, or the Arndt'sche Sturzmaschine (c. 1920).

Karlsbad-style coffee makers
A variant of the category of French drip coffee pots is the group of "Bohemian" coffee pots including the original Karlsbad coffee makers, historically produced by several mostly Bohemian porcelain manufacturers since 1878 up into the first half of the 20th century, and variants produced by Porzellanfabrik Siegmund Paul Meyer (SPM) / Porzellanfabrik Walküre since 1910,    Friesland Porzellan (FPM). In contrast to French drip coffee pots which feature round holes, they all use a special double-layered cross-slitted strainer made from through-glazed porcelain. Before World War I, they were very popular in the Viennese coffee house culture. The special kind of drip coffee they produce is called a Karlsbader ("Karlsbad coffee").

System Büttner coffee makers
System Büttner coffee makers are a type of coffee makers featuring a special permanent through-glazed porcelain filter with triangularly-arranged slits and a valving mechanism to combine steeping with drip-brewing. They were invented in 1926 by the coffee roaster Carl A. Büttner (Berlin, Germany) and produced up into, at least, the 1940s by the porcelain manufacturer Bauscher (company) (Weiden, Germany) for various German coffee roasters and distributors.

Electric drip-coffee makers
One of the first electrical drip coffee makers was the German Wigomat, patented in 1954. In the early 1970s electrical drip coffee makers became more common, causing a decline in manual drip coffee preparation methods until the 2010s, and the near-extinction of coffee percolators. Among the early electrical drip coffee machines was a machine designed by two former Westinghouse engineers and sold under the brand Mr. Coffee in the early 1970s.

It normally works by admitting water from a cold-water reservoir into a flexible hose in the base of the reservoir leading directly to a thin metal tube or heating chamber (usually, of aluminium), where a heating element surrounding the metal tube heats the water. The heated water moves through the machine using the thermosiphon principle. Thermally induced pressure and the siphoning effect move the heated water through an insulated rubber or vinyl riser hose, into a spray head, and onto the ground coffee, which is contained in a brew basket mounted below the spray head. The coffee passes through a filter and drips down into the carafe. A one-way valve in the tubing prevents water from siphoning back into the reservoir. The carafe, usually made of glass, rests on a warming plate that keeps the brewed coffee warm. A thermostat attached to the heating element turns off the heating element as needed to prevent overheating the water in the metal tube (overheating would produce only steam in the supply hose), then turns back on when the water cools below a certain threshold. For a standard 10–12 cup drip coffeemaker, using a more powerful thermostatically controlled heating element (in terms of wattage produced), can heat increased amounts of water more quickly using larger heating chambers, generally producing higher average water temperatures at the spray head over the entire brewing cycle. This process can be further improved by changing the aluminium construction of most heating chambers to a metal with superior heat transfer qualities, such as copper.

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, drip stop, and even built-in coffee grinding mechanisms.