The Karlsbad coffee maker
A coffee maker made entirely of porcelain whose filter is a slotted porcelain grid, with no paper or metal, topped by a water distributor. It is the filter coffee of Viennese and Bohemian homes, poured by hand in a service that is also the carafe.
How can a porcelain filter hold back the grounds?
Start the scene or choose a stage. The animation simplifies the mechanism; what follows gives the details and the available references.
The bottom of the filter is a double wall of porcelain slotted in a cross. There is neither paper nor metal between the coffee and the pot.
Read the stages without animation
- The slotted gridThe bottom of the filter is a double wall of porcelain slotted in a cross. There is neither paper nor metal between the coffee and the pot.
- Flaring slotsEach slot is very fine on the side of the grounds and widens toward the underside. The grounds stay on top, and nothing gets wedged in the slot.
- Grind coarseA coarse grind rests on the grid, more abundant than with paper, 8 to 10 g per cup. The grains do not pass through, but more coffee is needed.
- The distributorWater poured onto a disc pierced with large holes falls like rain on the grounds. The bed is not dug into, the water passes through it everywhere.
- ServeThe filter is lifted off, the lid is put on the porcelain pot. The coffee is served from the pot it dripped into.
To remember: A slot that is fine at the top and wide at the bottom holds the grounds without ever clogging: you only have to grind coarse, and use more.
In history: In 1878, at the porcelain factory of Count Oswald von Thun, in Klösterle, Bohemia.
Read the full article and its sources ↓History
German patent 3105, “innovations in the manufacture of porcelain sieves,” was filed on April 4, 1878 by the privileged porcelain factory of Count Oswald von Thun, in Klösterle, Bohemia, today Klášterec nad Ohří (source 1). Ukers writes in 1922 that the first Vienna coffee machine “seems to have been patented in Germany in 1879” (source 2); the one-year gap probably comes from the difference between filing and publication, which the record consulted does not specify.
Ukers describes the device without dating it. Known in the United States as the Bohemian coffee maker and elsewhere under the name Karlsbad, it is made of porcelain, and its European maker holds a patent on the grid: very fine slots on the inner side, which widen toward the outside to hold back well and be easy to clean. He adds that it “met with much favor” in America (source 2).
The article in the online encyclopedia Wikipedia, for want of better, gives the sequel: other porcelain makers take up the principle, the pear shape number 599 of the SPM factory, which became Walküre, becomes standard from 1913, and the coffee maker reigns in Viennese cafés before electric machines make people forget it; a revival begins around 2000 (source 3). These facts were not verified in the manufacturers' catalogs, whose sites refused access on the day of the search.
The motion
The device has four porcelain pieces: the pot, the filter, the water distributor and the lid (source 3). The filter grid is double, slotted in a cross and glazed throughout; the distributor, pierced with large round holes, spreads the water and avoids stirring the grounds (source 3).
A coarse grind goes into the filter, about 8 to 10 g per cup, a little water is poured to let the grounds bloom, then the rest in several stages onto the distributor (source 3). In 1917, Aborn noted that a porcelain sieve cannot be as fine as a metal sieve nor hold back a grind as fine as cotton can: more coffee is therefore needed for the same strength (source 2).
The settings
- Grindcoarse (source 3); a porcelain sieve does not hold back a fine grind (source 2)
- Dose8 to 10 g per cup (source 3)
- Brew rationot documented, the cup size not being given (source 3)
- Temperaturenot documented in the sources read; in 1921, Prescott preferred 85 to 93 °C to boiling water (source 2)
- Timenot documented in the sources read
- Pressurenone: gravity alone
What it has going for it
- Everything is porcelain: nothing imparts taste, and Prescott in 1921 put porcelain and glass at the head of the materials for making coffee (source 2).
- There is no paper to buy and no cloth to maintain, and the grid washes like a plate.
- The slots that widen toward the outside were designed to hold back the grounds while being easy to clean (source 2).
- The distributor keeps the pouring from digging into the grounds (source 3).
What is held against it
- The grid does not hold back a fine grind: you must grind coarse and use more coffee for the same strength (source 2).
- Porcelain breaks, and a slotted grid can be replaced only with a piece of the same shape.
- Parts are hard to find: the last major maker, Friesland, saw its Varel factory burn on June 29, 2023, according to the online encyclopedia (source 3).
What it gives in the cup
Without paper, the grid lets through more oils than a paper filter; its very fine slots nevertheless hold back most of the grounds (source 2). A rounder cup than with paper and a clearer one than with a French press can be expected; this is a deduction from the mechanism, as no measurement of yield, concentration or diterpenes specific to this coffee maker was found.
The coarse grind, imposed by the grid, calls for more coffee (source 2), which goes with a contact long enough for the water to extract these large particles.
Anecdotes
- In 1922, Ukers uses “Vienna coffee machine” for two different devices: the Karlsbad porcelain coffee maker, and the percolator used in Austrian homes (source 2).
The sources for this sheet
- Graf Oswald von Thun'sche Porzellanfabrik, Klösterle in Böhmen, German patent DE 3105 “Neuerungen in der Herstellung von Porzellansieben,” filed April 4, 1878, DEPATISnet bibliographic record (patent text not read) · online · primary · reading: record
- William H. Ukers, All About Coffee, New York, 1922, ch. XXXIV (German devices, 1877 to 1885; Bohemian or Karlsbad coffee maker), ch. XXXV (Austria) and ch. XXXVI (Aborn 1917; Prescott 1921) · online · primary
- Wikipedia (en), “Karlsbad-style coffee maker,” accessed October 21, 2026 · online · tertiary