Karlsbad-style coffee maker

A variant of the category of French drip coffee pots is the group of "Bohemian" coffee pots, manual zero-bypass flat bottom coffee makers made out of porcelain only, including Karlsbad coffee makers (since 1878),      Bayreuth coffee makers (since 2007),   the Walküre cup filter (2010)   and the Walküre aroma-pot (2015). In contrast to French drip coffee pots they all use a special double-layered cross-slitted strainer made from through-glazed porcelain  as well as a water spreader with six (or, in the larger models, more) large round holes to ensure an even water distribution and reduce the agitation of the coffee bed, a method sometimes also called cake filtration. In particular before World War I, but still up to the advent of the Espresso machine in the 1950s, they were very popular in the Viennese coffee house culture. The special kind of drip coffee they produce is called a Karlsbader ("Karlsbad coffee"). In Vienna, the Kleiner Schwarzer (confusingly also called Mokka or Piccolo), a black coffee without milk or sugar, was often prepared in Karlsbad coffee makers as well.

History
The original so called Karlsbad coffee maker was produced by the Thun Karlovarsky of Klösterle an der Eger (now Klášterec nad Ohří) near Karlsbad (now Karlovy Vary),     which patented a special filter sieve in 1878.

Karlsbad coffee makers were historically manufactured by many porcelain manufacturers including Thun Karlovarsky (TK) (Karlsbad),      Altrohlauer Porzellan-Fabriken AG vorm. Moritz Zdekauer (M&thinsp;Z) (Stará Role), EPIAG (EPIAG D.&thinsp;F.) (Dallwitz), Georg Haas von Hasenfels & Johann Czjzek von Smidaich (H.&thinsp;&&thinsp;C.) (Schlaggenwald), Carl Tielsch (C.&thinsp;T.) (Altwasser), Hutschenreuther (Selb / Bavaria, Germany), Rosenthal & Co. (R.&thinsp;C.) (Bavaria, Germany) / Rosenthal (Weiden/Kronach, Germany),   Bauscher (company) (Weiden, Germany), Carl Teichert (MEISSEN) (Meißen, Germany), Villeroy & Boch (V.&thinsp;B.) (Luxemburg), Fayencerie Sarreguemines (France), Pillivuyt (France), and Porzellanfabrik Siegmund Paul Meyer (SPM) / Porzellanfabrik Walküre (Bayreuth, Germany) / Friesland Porzellan (FPM) (Varel, Germany).

Karlsbad coffee makers consist of four parts (a coffee pot, a coffee strainer/filter, a water spreader/distributor, and a lid) all made out of porcelain, and they exist in a number of different shapes of unknown origin. The original shape appears to have been a cylindrical filter with two squarish handles combined with a ball-shaped pot. Another style featured a somewhat trapezoid shape known as neukonisch ("neoconic").

In 1910, SPM incorporated the slitted Karlsbad filter into the design of a coffee maker with cylindrical filter (form 523). In 1913, SPM introduced the now classical somewhat pear-shaped rounded form (form 599). This design was copied by other porcelain manufacturers. Over the years it was available in various sizes ranging from 250 ml to 2.25 litres.

In 2007, the so-called Bayreuth coffee makers were created by designer Daniel Eltner for Walküre. A slick modernized style (form 699) following the same general four-piece porcelain construction principles as traditional Karlsbad coffee makers, the design received the "Good Design Award 2008" of the Chicago Athenaeum Museum of Architecture and Design and the "Coffee Innovations Award 2008" in the category "coffee machines and mills" at the domotechnica fair in Cologne. However, due to its non-symmetrical design it may be difficult to handle for left-handers. It has been available in two sizes (350 ml and 700 ml) produced by Walküre up to 2019,       and since 2020 by Friesland (400 ml and 700 ml).

, Friesland was the only remaining manufacturer of any of them, however, their Varel production site burnt down in a fire in June 2023,    pending its reconstruction.

Preparation
To avoid clogging, coarsly ground coffee with about salt- or sugar-sized grains (about semolina-grade), ideally evenly ground and without fines or added coffee surrogates, has to be used.

Forms and sizes
Siegmund Paul Meyer (1899–1920) (SPM):
 * Form 523/1 (1910–1940): ? (smallest)
 * Form 523/2 (1910–1940): ?
 * Form 523/3 (1910–1940): ?
 * Form 523/4 (1910–1940): ?
 * Form 523/5 (1910–1940): ?
 * Form 523/6 (1910–1940): ?
 * Form 523/7 (1910–1940): ? (largest)
 * Form 599/0: c. 2.0 l (20? cups) (largest)
 * Form 599/1 (1913–?): c. 1.6 l (old)
 * Form 599/1 (?–1942) : c. 1.8 l (new)
 * Form 599/2 (1913–1942): ?
 * Form 599/3 (1913–1942): ?
 * Form 599/4 (1913–1942): ?
 * Form 599/5 (1913–1942): ?
 * Form 599/6 (1913–1942): ?
 * Form 599/7 (1913–1942): ? (smallest)
 * Form 628 (1928–1942): ?
 * Form 629 (1929–1942): ? (cup filter)
 * Form 800 (1957–1965): ? (aroma pot)

Porzellanfabrik Walküre (1920–2019):


 * Form 599-028 (?–2019): 280 ml
 * Form 599-038 (?–2019): 380 ml
 * Form 599-085 (?–2019): 850 ml
 * Form 599-115 (?–2019): 1150 ml
 * Form 699-035 (2007–2019): 350 ml
 * Form 699-070 (2007–2019): 700 ml
 * Form 799-020 (2010–2019): 200 ml (cup filter)
 * Form 890-050 (c. 2017): 500 ml (tea pot)
 * Form 890-100 (c. 2017): 1000 ml (tea pot)
 * Form 899-050 (c. 2017): 500 ml (tea pot)
 * Form 899-100 (c. 2017): 1000 ml (tea pot)
 * Form 999-035 (2015–2019): 350 ml (aroma pot)

Friesland Porzellan (FPM):
 * Form "599" (2020–2021): 380 ml, 850 ml
 * Form "599" (2021–2023): 250 ml, 350 ml, 800 ml, 1100 ml
 * Form "699" (2020–2023): 400 ml, 700 ml
 * Form "799" (2020–2023): 200 ml  (cup filter)

Rosenthal (similar to SPM/Walküre form "599" without ribs):
 * Size 0: 2250 ml (12 cups)
 * Size 1: 1750 ml (8 cups)
 * Size 2: 1350 ml (6 cups)
 * Size 3: 1100 ml (5 cups)
 * Size 4: 800 ml (4 cups)
 * Size 5: 500 ml (3 cups)
 * Size 6: 350 ml (2 cups)
 * Cup filter: ? (1 cup)

Hutschenreuther (similar to SPM/Walküre form "599" without ribs):
 * Size 5: 1.25 l (with filter), 1.4 l (pot only)


 * Size 7: ?
 * Size 8: 1.5? l

Georg Haas von Hasenfels & Johann Czjzek von Smidaich (H.&thinsp;&&thinsp;C.), Schlaggenwald:
 * Size 4 (1942): c. 850 ml

TK Thun (Thun Karlovarsky):
 * Size 4: c. 950 ml

Unidentified:
 * Form "599" size 8: c. 1/8 l (1 cup)
 * Form "599" size 5½

Similar coffee makers
In the 1880s, Max Thürmer, a coffee roaster of Dresden, Germany, advertised Karlsbad coffee and somewhat later also coffee makers in various newspapers. In the early 1900s, he marketed his own invention of a manual coffee maker (the so called Kaffeeaufgußkanne Max Thürmer), which, from its outer appearance, looked quite similar to cylindrical Karlsbad coffee makers but featured an air-tight joint (through a lid with a thin film of water) between the permanent filter part and the coffee pot below, and it came with a manual valving mechanism (by closing the spout (teapot) of the coffee pot) to combine steeping (full immersion) with drip-filtering (percolation). The devices were manufactured by Villeroy & Boch for him. While the permanent filter in early of his devices still featured round drilled holes like in French drip coffee makers, later units used a double-layered cross-slitted filter construction similar to that found in Karlsbad coffee makers, but with a much coarser grid, with a large air gap between the layers, and using ceramics instead of porcelain.

Since 1926, the idea to combine steeping with drip-filtering was also utilized by Berlin-based coffee roaster Carl Artur Büttner in his invention of a manual coffee maker. While his construction was considerably different, it also featured a valving mechanism (through a rotatable saucer), a through-glazed porcelain filter with triangularly-arranged slits and with an air space below. These so called "System Büttner" coffee makers were available up into, at least, the 1940s as stand-alone devices for home use, but were also adopted by various other German coffee roasters as part of larger coffee machines produced by the porcelain manufacturer Bauscher (company) for heavy-duty batch use in restaurants and canteens.

Since c. 1952 (and up into the 1970s) the Neuerer Porzellanfabrik in Oberkotzau, Germany, the successor of Porzellanfabrik Greiner & Herda, manufactured coffee percolators named Aromator, which featured double-layered cross-slitted porcelain filters similar to those used in Karlsbad coffee makers, and thus not requiring any paper filter rings.

Modern manual coffee makers sometimes associated with Karlsbad-style coffee makers include Coffee Consulate's intense extraction cup filter RS16 GlasFilter by Steffen Schwarz (2015) and the borosilicate carafe coffee maker "The Pure Over" by glass artist Etai Rahmil (2020). However, whilst they are zero-bypass flat-bottom French drip coffee pots with permanent filters, they too cannot be counted as Karlsbad-style coffee makers because they do not feature a cross-slitted double-layered filter sieve and also because they are not made out of porcelain.