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Equipment · Brew method

Moka pot

A stove-top coffee maker in which heated air and vapour in a closed lower chamber push water up through a bed of ground coffee into an upper chamber, at far lower pressure than an espresso machine.

Across the chain: History · Science · Equipment

Source-checkedby Coffearium verification pass· Last source-checked 15 Oct 2026· Prepared with AI assistance· 13 sources (9 tier A)· 2 contested· Updated 15 Oct 2026
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Contents
  • A moka pot has a boiler for water, a funnel for the coffee and a collector for the brew; heated air and vapour push the water up.1,2
  • The European standard EN 13248 covers these coffee makers and sets a working pressure between 0.5 and 2.5 bar; espresso pumps build higher pressures.2,3
  • In one study, water was already flowing to the coffee when the boiler water was at about 69–70 °C, well below boiling; it reached 117–121 °C by the end.1
  • In a nine-method comparison, moka coffee held 2.13% total solids, between espresso (above 4%) and filter coffee (1.03%), with the highest extraction yield of all methods.4
  • Alfonso Bialetti invented the moka pot in 1933.1,3,13

How a moka pot works#

A moka pot is a stove-top coffee maker made of a lower tank, a funnel-shaped filter, a gasket, a filter plate and an upper pot.1 The lower part is a closed boiler that holds the water.1,2 Above it sits a funnel-shaped filter with the ground coffee, partly inside the boiler and reaching down into the water.1,5 On top, the collector receives the brew through a pipe that rises from the filter plate.1,5 A rubber gasket seals the collector to the boiler.1

The pot is heated from below. The air and water vapour above the water warm up, and their pressure rises.1 This pressure pushes the water down, up the stem and through the coffee bed.1,3 The brew then rises through the pipe and collects in the upper chamber.1,5 A filter plate under the collector stops the grounds from rising with the liquid.5

The water does not need to boil. In one study, water was already flowing to the coffee when the boiler water was at about 69–70 °C.1 The authors call the belief that boiling is needed a misbelief; the air trapped in the boiler does much of the pushing.1

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  1. Boiler. Holds the water for the brew and is heated from below.1,2 In one study, a three-cup pot had a 220 cm³ boiler.1
  2. Air and vapour. As they heat up, their pressure pushes the water up the stem. Dry air contributes most of this push.1
  3. Safety valve. A pressure-release valve on the boiler.5 EN 13248 defines the safety device as one that keeps the internal pressure below the safety pressure.2
  4. Funnel stem. The lower part of the funnel reaches down into the boiler water; the water rises through it to the coffee.1,5
  5. Coffee bed in the funnel. The funnel-shaped filter holds the ground coffee.1,5 According to a coffee science textbook, the coffee is not compacted.3
  6. Filter plate and gasket. The plate stops the grounds from rising with the brew5; the gasket seals the collector to the boiler.1,2
  7. Spout. A pipe that carries the brew up from the filter plate into the collector.5
  8. Collector. The upper chamber, where the brew collects.1,2
A moka pot cut open along its axis; the dashed line follows the water from the boiler to the collector. Schematic, not to scale.

Pressure and the safety valve#

A moka pot works at low pressure. The European standard for these coffee makers, EN 13248, covers pots that make coffee under steam pressure above 0.5 bar and below 2.5 bar.2 It requires a working pressure between 0.5 and 2.5 bar when tested.2 According to a coffee science textbook, an espresso pump builds higher pressures than the vapour chamber of a moka pot.3 The espresso machine entry covers pump pressure.

The safety valve sits on the boiler.5 EN 13248 defines the safety device as a device that prevents the internal pressure from exceeding the safety pressure.2 The safety pressure is the highest pressure the device allows in operation.2 The standard also tests the sealing system between boiler and collector.2 The opening pressure of the valve was not in the part of the standard opened for this entry, so no value is given.

Extraction compared with espresso and filter#

Moka coffee is strong, but weaker than espresso. In a 2013 comparison of nine methods, moka coffee held 2.13% total solids.4 Espressos held more than 4%, French press coffee 1.43% and filter coffee 1.03%.4 The authors note that 2.13% is, strictly speaking, too low for an espresso.4

The same study measured the highest extraction yield for the moka pot: 31.2% of the coffee dissolved, against 26% for the French press.4 This yield comes from oven-dried total solids, so it is not comparable with refractometer readings (see the extraction yield entry). The authors suggest the higher extraction temperature as a reason.4 A coffee science textbook gives the same explanation.3

The moka coffee had no crema, middle-range sensory scores and the same flavour profile as the capsule coffee in that study.4 According to the textbook, moka coffee can have a harsh character because of the high extraction temperatures. A skilled brewer can balance it by moderating temperature and grind.3

5060708090100110120130°CWater in the boiler, 400 W68.7 → 117.2 (mean 94.3)1 Water in the boiler, 600 W70.2 → 120.6 (mean 97.6)1 Coffee in the spout, 400 W63.0 → 95.8 (mean 78.8)1 Coffee in the spout, 600 W61.8 → 97.7 (mean 80.5)1
Data table
°CSource
Water in the boiler, 400 W68.7 → 117.2 (mean 94.3)1
Water in the boiler, 600 W70.2 → 120.6 (mean 97.6)1
Coffee in the spout, 400 W63.0 → 95.8 (mean 78.8)1
Coffee in the spout, 600 W61.8 → 97.7 (mean 80.5)1
Temperatures in a three-cup moka pot on a 400 W and a 600 W electric hob, means of 10 runs each.1 Boiler water was measured from 10 g to 120 g of water flowed, the coffee in the spout from 50 g to 120 g.1 The boiler water passed 100 °C during extraction; the coffee did not.

Caffeine and strength#

How much caffeine a moka cup holds depends on the coffee, the dose and the cup size. The caffeine entry explains the general rules.

  • Per cup. In the nine-method comparison, a 30 mL cup of moka coffee held 21.6 mg of caffeine. That was the least of the four 30 mL methods.4
  • Per serving, across studies. A 2021 review groups moka with other coffee percolator brews. For arabica, it gives 14–67 mg per 40 mL.7
  • Left in the grounds. Spent moka grounds still held 16.4% of the coffee’s caffeine. Household filter grounds held 5.6%, grounds from restaurant high-pressure machines 21.5–30.8%.6

The studies used different coffees and recipes, so they do not rank the methods (see Contested). In the spent-grounds study, the moka ratio and contact time were unknown.6

Aluminium and stainless steel#

The classic moka pot is made of aluminium.1,12,13 Pots of stainless steel also exist, and one migration study tested one alongside three aluminium pots.8 EN 13248 requires that materials in contact with water, coffee and brew do not adversely affect the sensory properties of the brew.2

What the authorities state. In 2008, the European Food Safety Authority (EFSA) set a tolerable weekly intake (TWI): 1 mg aluminium per kg body weight per week.10 EFSA stated that this TWI is likely to be exceeded in a significant part of the European population.10 For metals and alloys in food contact materials, a 2013 Council of Europe resolution, CM/Res(2013)9, gives a specific release limit (SRL) of 5 mg aluminium per kg of food.9,11 The German Federal Institute for Risk Assessment (BfR) states that these release limits are recommendations only.11 The BfR states that the transfer of aluminium from food contact materials to food is low when they are used properly.11

What was measured. A 2017 study brewed coffee six times in each of four moka pots. The pots were washed in a dishwasher after the fifth brew.8 In the aluminium pots, aluminium in the coffee fell over the first brews, most after the first and second, and rose highly significantly after the dishwasher wash.8 The aluminium pots gave higher aluminium levels than the stainless steel pot in all 18 paired comparisons, 13 of them significant.8 The authors calculated that coffee from an aluminium moka pot contributes at most 4% of the TWI for a 70 kg adult drinking 3.17 L of coffee per week, the average German consumption.8 This held even for pots washed in a dishwasher against the manufacturers’ explicit instructions.8

Making moka coffee#

These steps describe the method as the sources report it. The quantities are examples from studies, not recommendations.

  1. Fill the boiler with water up to the level the manufacturer specifies; EN 13248 defines the usable volume of a pot this way.2 Example: one study used 150 g of water in a three-cup pot.1
  2. Fill the funnel with ground coffee and level it without pressing; a textbook lists no compaction and a medium grind for the moka pot.3 Example doses: 15 g of coarsely ground coffee for stove-top makers1, or 7.5 g for 110 mL of water.4
  3. Screw the collector onto the boiler so that the gasket seals the joint.1
  4. Heat the pot from below. Example: the 2009 study used an electric hob at 400 W or 600 W.1 In the 2013 comparison, a three-cup pot took 224 ± 12 s.4
  5. End the brew in time. According to the textbook, this is when the first water has come up and the brew is dark and syrupy.3 A patent background notes that the stove must be turned off promptly once the coffee has risen.5 A rattling sound marks the late phase, which spoils the cup (see Deep dive).1,3

The example recipes work out at about 15 mL of water per gram of coffee (2013) and 10 g per gram (2009), by our own arithmetic.1,4

History#

The moka pot was invented by Alfonso Bialetti in 1933.1,3,13 A 2009 study describes him as an aluminium technologist and states that his son Renato commercialised the pot from 1946.1 According to a coffee historian, the aluminium stove-top brewer then became popular throughout Italy as coffee drinking at home increased.12 The same historian notes that its publicity claimed coffee of the same quality as at the bar, inaccurately, since the pressures in the pot were much lower.12 A 2017 textbook calls it the most popular household brewing method in Italy.3 The European standard EN 13248 for these coffee makers was approved on 23 October 2002.2

Thermodynamics of the boiler#

A common account holds that the water must reach its atmospheric boiling point to drive it out, and that the pressure rise comes from equilibrium between water and its vapour.1 A 2009 study measured temperatures and pressure in a three-cup pot to test this.1 At the start, the boiler held 20 cm³ of air above the water.1 A noticeable pressure rise appeared when the water was at about 90 °C.1

The gas above the water was considerably cooler than the water itself, which shows that water and vapour were not in thermodynamic equilibrium.1 The authors conclude that dry air makes the major contribution to driving the extraction.1 Extraction therefore starts at fairly low temperatures and depends on the amount of dry air in the boiler at the start.1 The amount of air can change both temperature and flow rate, and with them the quality of the brew.1

Measured temperatures. In 10 runs each on a 400 W and a 600 W electric hob, the boiler water was measured between 10 g and 120 g of water flowed, and the brew in the spout between 50 g and 120 g.1

Parameter 400 W 600 W Source
Boiler water, initial (°C, mean ± SD) 68.7 ± 2.7 70.2 ± 2.9 Navarini et al.1
Boiler water, final 117.2 ± 1.2 120.6 ± 3.0 Navarini et al.1
Boiler water, mean 94.3 ± 1.6 97.6 ± 1.2 Navarini et al.1
Brew in the spout, initial 63.0 ± 2.0 61.8 ± 2.5 Navarini et al.1
Brew in the spout, final 95.8 ± 2.9 97.7 ± 2.4 Navarini et al.1
Brew in the spout, mean 78.8 ± 1.5 80.5 ± 1.3 Navarini et al.1

The study used 15 g of a 100% arabica blend, roasted medium (16% weight loss) and coarsely ground for stove-top makers, with 150 g of water.1 Pressure was read with a differential transducer with a 0–7 bar range; the paper does not state the reference pressure, so its readings are not given here as absolute or gauge values.1

Phases of extraction#

The 2009 study divides the brew into two phases.1 The first drop of brew reached the sensor in the spout after the funnel had filled completely, when about 40 g of water had left the boiler.1

  • Regular extraction phase. Water passes through the bed as liquid, up to about 120 g of water flowed in that study.1 According to a coffee science textbook, this phase is driven by rising air–vapour pressure in the boiler; pressure rises with flow rate and as the bed becomes less permeable.3
  • Strombolian phase. When little water is left, a noisy mixture of boiling water and vapour flows from the spout, announced by a rattling sound.1,3 The study calls the passage of these hot fluids through the bed harmful to the quality of the brew.1 Higher pressure and temperature extract more undesired compounds.1 According to the textbook, this raises bitterness and astringency and strips less volatile, unpleasant odorants into the cup.3

The textbook describes the extraction as hard to control and quick to over-extract, which is why the brew must be ended in time.3

The coffee bed#

The bed is not a fixed filter. In the 2009 study, its permeability fell gradually during the brew towards a steady value, as the coffee changed.1 A coffee science textbook attributes the fall to swelling of the coffee particles.3 During the regular phase it lay at 70–400 mD (millidarcy).1 In SI units that is about 6.9 × 10⁻¹⁴ to 3.9 × 10⁻¹³ m² (our own conversion, 1 D ≈ 9.87 × 10⁻¹³ m²), the same order as packed espresso beds reported in the espresso machine entry. The study reports an earlier value more than ten times higher (see Contested).1

According to the textbook, pressure on any coffee bed is not set independently: it results from the force on top of the bed and the bed’s resistance to flow.3 In a moka pot, the force comes from a pressurised chamber of steam and vapour, and the pressures are somewhat lower than with an espresso pump.3

Reference values#

Parameter Value reported Context Source
Working pressure 0.5–2.5 bar Scope and requirement of EN 13248 CEN2
Boiler volume; funnel volume 220 cm³; 50 cm³ Three-cup pot Navarini et al.1
Air in the boiler at the start 20 cm³ 150 g water fill Navarini et al.1
Noticeable pressure rise Water at about 90 °C Electric hob Navarini et al.1
First brew in the spout After about 40 g of water flowed Funnel completely filled Navarini et al.1
End of regular phase About 120 g of water flowed 150 g water fill Navarini et al.1
Boiler water 68.7–70.2 °C initial; 117.2–120.6 °C final (means) 400 and 600 W Navarini et al.1
Brew in the spout 61.8–63.0 °C initial; 95.8–97.7 °C final (means) 400 and 600 W Navarini et al.1
Bed permeability 70–400 mD Regular extraction phase Navarini et al.1
Dose and water 15 g coffee, 150 g water Three-cup pot Navarini et al.1
Dose and water 7.5 ± 0.1 g coffee, 110 mL water Three-cup pot, three brews combined per sample Gloess et al.4
Dose and water 11.3 g coffee, 80 mL water, 62 mL brew, 3 min One study, as summarised in a review Olechno et al.7
Brew time 224 ± 12 s Three-cup pot Gloess et al.4
Total solids 2.13 ± 0.01% Oven-dried Gloess et al.4
Extraction yield 31.2% From total solids Gloess et al.4
Caffeine per 30 mL cup 21.6 mg Same coffee as the other methods Gloess et al.4
Caffeine in the brew 1.680 ± 0.200 g/L One study, as summarised in a review Olechno et al.7
Caffeine left in spent grounds 16.4% (2.1 mg/g grounds) Ratio and contact time unknown Vandeponseele et al.6
Aluminium, share of TWI At most 4% 70 kg adult, 3.17 L coffee per week, aluminium pots Stahl et al.8

The 2013 comparison gives no temperature or pressure for the moka pot.4 The same paper states that moka coffee was the least acidic brew, with the highest pH, but its ordering of pH values ends with the French press; this entry gives no pH for moka coffee.4

Open questions#

  • Pressure over time. The 2009 study plotted pressure against time, but the values were read from figures only and its reference pressure is not stated, so no pressure curve is shown here.1 No openly available peer-reviewed table of moka pressure over time was found.
  • Heat input and quality. The study links the amount of air, temperature and flow rate to extract quality.1 No sensory study opened for this entry varied heat input or fill level at a fixed recipe.
  • Valve opening pressure. The value at which the safety device must open was not in the part of EN 13248 opened for this entry.2
  • Stainless steel pots. The migration study included one stainless steel pot and reports it only in comparison with the aluminium pots, without its own aluminium levels.8 No study opened for this entry measured several stainless steel pots.

Key studies#

Navarini et al., 2009 – Thermodynamics of the moka. Measured water, gas and brew temperatures, pressure and flow in a three-cup moka on an electric hob. Extraction started well below 100 °C, driven mainly by the air trapped in the boiler, and the bed’s permeability fell during the brew; the late strombolian phase harmed quality.

Applied Thermal Engineering 29, 998–1004 · doi:10.1016/j.applthermaleng.2008.05.014

Gloess et al., 2013 – Nine methods side by side. Brewed one coffee by nine methods, including a three-cup moka pot, and measured strength, yield, caffeine, aroma and sensory profile. The moka pot gave the highest extraction yield, 2.13% total solids and no crema.

European Food Research and Technology 236, 607–627 · doi:10.1007/s00217-013-1917-x

Stahl et al., 2017 – Aluminium from moka pots. Brewed coffee six times in three aluminium pots and one stainless steel pot, with a dishwasher wash after the fifth brew. Aluminium in the coffee fell over the first brews and rose after the wash; for a 70 kg adult drinking 3.17 L a week it reached at most 4% of the EFSA tolerable weekly intake.

Environmental Sciences Europe 29, 18 · doi:10.1186/s12302-017-0118-9

Vandeponseele et al., 2021 – Caffeine left in spent grounds. Measured the caffeine remaining in spent grounds from several brew methods. Moka grounds kept 16.4% of the caffeine, between a household filter and restaurant espresso machines.

Clean Technologies 3(2), 335–350 · doi:10.3390/cleantechnol3020019

Contested
  • Caffeine in moka coffee compared with other methods: in a nine-method comparison, moka coffee had the least caffeine of the four methods compared per 30 mL cup, 21.6 mg4; a review cites a study in which moka coffee held more caffeine per litre than coffee from a filter machine7; and spent moka grounds kept 16.4% of the caffeine, against 5.6% for a household filter.6 Recipes, coffees and bases (per cup, per litre, per gram of grounds) differ, so the figures do not rank the methods.
  • Permeability of the moka coffee bed: one study measured 70–400 mD (millidarcy) during the regular extraction phase and reports that this is more than ten times lower than the 2,300 mD of an earlier study.1 The earlier study was not opened for this entry.
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Sources

  1. ANavarini, L.; Nobile, E.; Pinto, F.; Scheri, A.; Suggi-Liverani, F. (2009). Experimental investigation of steam pressure coffee extraction in a stove-top coffee maker. Applied Thermal Engineering 29(5–6), 998–1004. doi:10.1016/j.applthermaleng.2008.05.014 · other copies
  2. AEuropean Committee for Standardization (CEN) (2002). EN 13248:2002 Cookware – Coffee makers for domestic use with an independent heat source – Definitions, requirements and test methods. CEN; approved 23 October 2002 (preview of the Slovenian adoption SIST EN 13248:2003).
  3. BMestdagh, F.; Glabasnia, A.; Giuliano, P. (2017). The Brew – Extracting for Excellence. In: Folmer, B. (ed.), The Craft and Science of Coffee, Academic Press, ch. 15, pp. 355–380. doi:10.1016/B978-0-12-803520-7.00015-3 · other copies
  4. AGloess, A. N.; Schönbächler, B.; Klopprogge, B.; D’Ambrosio, L.; Chatelain, K.; Bongartz, A.; Strittmatter, A.; Rast, M.; Yeretzian, C. (2013). Comparison of nine common coffee extraction methods: instrumental and sensory analysis. European Food Research and Technology 236, 607–627. doi:10.1007/s00217-013-1917-x · other copies
  5. A/BGiacchino, M. (2017). Improved moka pot provided with a non-metallic boiler (EP 3 130 263 A1). European Patent Office; Italian priority 10 August 2015, published 15 February 2017.
  6. AVandeponseele, A.; Draye, M.; Piot, C.; Chatel, G. (2021). Study of Influential Parameters of the Caffeine Extraction from Spent Coffee Grounds: From Brewing Coffee Method to the Waste Treatment Conditions. Clean Technologies 3(2), 335–350. doi:10.3390/cleantechnol3020019 · other copies
  7. AOlechno, E.; Puścion-Jakubik, A.; Zujko, M. E.; Socha, K. (2021). Influence of Various Factors on Caffeine Content in Coffee Brews. Foods 10(6), 1208. doi:10.3390/foods10061208 · other copies
  8. AStahl, T.; Falk, S.; Rohrbeck, A.; Georgii, S.; Herzog, C.; Wiegand, A.; Hotz, S.; Boschek, B.; Zorn, H.; Brunn, H. (2017). Migration of aluminum from food contact materials to food—a health risk for consumers? Part II of III: migration of aluminum from drinking bottles and moka pots made of aluminum to beverages. Environmental Sciences Europe 29, 18. doi:10.1186/s12302-017-0118-9 · other copies
  9. AStahl, T.; Falk, S.; Rohrbeck, A.; Georgii, S.; Herzog, C.; Wiegand, A.; Hotz, S.; Boschek, B.; Zorn, H.; Brunn, H. (2017). Migration of aluminum from food contact materials to food—a health risk for consumers? Part I of III: exposure to aluminum, release of aluminum, tolerable weekly intake (TWI), toxicological effects of aluminum, study design, and methods. Environmental Sciences Europe 29, 19. doi:10.1186/s12302-017-0116-y · other copies
  10. AEuropean Food Safety Authority (EFSA) (2008). Safety of aluminium from dietary intake – Scientific Opinion of the Panel on Food Additives, Flavourings, Processing Aids and Food Contact Materials (AFC). EFSA Journal 754, 1–34. doi:10.2903/j.efsa.2008.754 · other copies
  11. AMüller, F. (Bundesinstitut für Risikobewertung, BfR) (2014). Aluminium-Exposition aus Lebensmittelkontaktmaterialien (presentation, 15th BfR Forum “Risiken durch Aluminium im Alltag”). German Federal Institute for Risk Assessment (BfR), 26 November 2014.
  12. BMorris, J. (2017). We Consumers – Tastes, Rituals, and Waves. In: Folmer, B. (ed.), The Craft and Science of Coffee, Academic Press, ch. 19 (p. 473 cited). doi:10.1016/B978-0-12-803520-7.00019-0 · other copies
  13. BThe Museum of Modern Art (MoMA), New York (2008). Alfonso Bialetti. Moka Express (object number 431.2008). MoMA collection record, Department of Architecture and Design.

Tier A · authoritative · B · trade and expert · C · general. Supporting quotes for every source are in the data version of this entry. If a publisher’s site refuses access, try the doi link or “other copies”.

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