Filter coffee machine 

Schematic representation of an electric filter coffee machine
The operating principle of a filter coffee machine is based on a bubble pump. The water passes through a built-in inlet hose check valve in a heated tube in the heating element of the hot plate. The inflowing cold water heats up vapor bubbles occur, and pressure builds, causing the check valve closes. The hot water rises through a tube top in another, usually pivotable pipe that runs through filters, and drip onto the ground coffee in the filter. The pressure in the heating tube decreases until the check valve opens, and a new cold water flows into the heat pipe and the process is repeated periodically. In the jug under the filter and the heating plate then collects the finished “filter coffee”.

If the cold water used in the water tank, the temperature of the heater tube increases to about 130 to 150 ° C; at this temperature, a temperature switch on the tube heating from either whole or regulates coffee machines with a warming function for the pot, in which the heat pipe is located just below the hotplate, then the temperature of the plate by cycling on and off, until the machine is manually turned off , In addition, a thermal fuse ensures that when failures no overheating can occur. She speaks at about 180 ° C.

Coffee machines need to heat the water more electricity than kettle because the steam escapes always a certain amount of energy. In addition the holding power comes after completion of the coffee.

Percolator 
The percolation is still a commonly used method to make coffee. The word comes from the Latin percolare, which means as much as strain, filtering.

Operation of a percolator

Percolater cooking

Electrical pumping percolator of AEG in 1930; Design: Peter Behrens
The coffee percolator was invented by Benjamin Thompson 1810-1814.

The invention of the modern coffee percolator with inner cylinder is attributed to the Parisian tinsmith Laurens. He developed in 1819 the first coffee pot, in which the water was heated on the stove and then ascended through an inner cylinder. This principle was widely accepted and changed. It has also experimented with closed systems, so-called Dampfdruckperkolatoren.

In America, where the filter method is not as well known, is prepared more often after Perkolationsprinzip coffee, as in England and the Netherlands. In Germany, the percolator is almost forgotten. However, some large coffee machines still work on this principle. The equipment for home use were mostly made of metal, simple designs made of aluminum, other chromium-plated or silver-plated brass. Since the coffee readily accepted the taste of metal, some manufacturers went over to partially manufacture the devices at least glass or not to produce porcelain. Electric coffee makers of porcelain were very common in the USA. In Germany Rosenthal introduced in the 1930s, her coffee machines. Widely used are mainly the “Special distillation column” mentioned devices innovators.

From operating principle, the percolator is clearly distinguishable from the filter jug. A simple percolator is a pot, inside which a metal tube is provided. On the upper third of this cylinder, an aluminum container is fixed, which is used as a coffee filter. In the lid of the can usually find a small glass dome, through which you can watch the brewing process. If the water is heated, it is pressed through the tube upward. Here it is dripping now from above on the ground material, and then mixed again with the water in the jug. This circulating process repeats itself and will not be stopped until the coffee has the desired thickness.

Of these circulating percolators the Pump percolators are to be distinguished, in which the water is used only once dropped on the ground material, and then collected in a separate container. These percolators therefore next to a “water tank” another container for the finished coffee, which is usually discharged through a small outlet tap.

A special form of pump-percolators is the known espresso pot that is heated on the stove. Unlike the classic pump-percolators here penetrates the water to coffee filters already in the ascent.

Examples of non-circulating percolators from German production are about: WMF (replica of the American firm Landers / Universal 1880-1930, heated both with alcohol, as well as electric); Graetzor (1930-1966); Linnschiff, Feldhaus (simple percolators from the 1950s), Rowenta (1920 till 1962) and many more.

Examples of known pump percolators are: AEG, (Germany, 1930 – design Peter Behrens); Moccadur (DDR, 1950s) and Therma (Switzerland, 1960).

Percolators be restored Jena glass also recently. These new percolators are equally suitable for gas, ceramic and electric stoves.

Vacuum maker

Operation of a vacuum heater

Electric vacuum heater. Links: USA around 1950, right: Hungary vs. 1920
A further development of the percolators are vacuum heaters, which are occupied for about 1830th It is known the so-called glass balloon. Two glass tubes are mounted above each other. The lower vessel, the top filled with water with coffee powder. If the lower vessel is now heated, the water rises through a riser into the upper vessel and mixes with the ground material. Now you delete the spirit lamp under the lower vessel so that there cools the air and a vacuum (vacuum), who withdraws the blended with the coffee water through a filter into the lower vessel. For this lower vessel of coffee can now, after the apparatus was disassembled, are served. With machines of this type, there were many accidents. You hear explosions and broken glass because the heat source was removed too late. Nevertheless, according to this principle, a number of different coffee machines was produced. Mostly the two containers were not transferred but side by side and provided with a tilting mechanism which automatically extinguished the corresponding alcohol burner.

In Germany won in the 20th century the glass Vacuum-maker in the design of the Bauhaus artists under the name Sintrax a larger distribution. Also common were the electrical appliances, the selling Rowenta in the 1950s. Over the past 30 years such devices came mainly from the Danish manufacturer Bodum.

Steam press 
Boiling water is forced into a closed container by its own pressure through a filled with coffee powder sieve. There is neither a pump nor a lever for generating the pressure. These devices were in the GDR in the 1980s marketed as “Kaffeeboy” AKA-Electric. In the early 1990s as “Espresso Machine” by manufacturers such as Krups, Braun and Tchibo. A precursor of these devices is the wigomat 203 / wigoespresso.

Espresso Machine
→ Main article: Espresso Machine

In the Coffee Maker water is heated in a heated boiler or heat exchanger to about 90 ° C and passed at about 9 bar pressure through finely ground coffee beans. The pressure is usually generated by an electric pump. This method is usually used for the preparation of espresso, but the machines are also suitable for almost all other coffees.

Pod coffee machine
→ Main article: pod coffee machine

For a portion of coffee machine
In the late 1990s, machines came onto the market in which the coffee is placed in pre-portioned form by means of so-called pads or capsules in a holder and filtered under pressure. Up to three cups of coffee are brewed simultaneously.

For more information on coffee makers of all sorts, check out Appliance Authority’s articles on coffee makers