# 9Barista Stovetop Espresso Source: https://dailyextraction.com/methods/9barista/ Last updated: 2026-10-20 > The 9Barista is a stovetop espresso maker with two boilers. The lower boiler builds up 9 bars of pressure; the upper boiler, open to the air, holds 100°C and cools the brew water, which a finned heat exchanger then brings to about 93°C. That water is pushed through about 20 g of finely ground, tamped coffee, giving roughly a 40 g espresso, with no pump or electronics. ## At a glance - Ratio: 1:2 (about 20 g in, 40 g out) (20 g coffee : 40 g water) - Grind: Extra fine - Water temperature: 93 °C - Category: Pressure & Espresso (Pressure) - Difficulty: Intermediate - Origin: United Kingdom, 2019 - Also known as: 9Barista, 9Barista espresso machine, jet-engineered stovetop espresso ## Steps 1. **Fill the lower boiler**: Fill the lower boiler with water to the fill line, about 120 ml. 2. **Screw on the middle section**: Screw the middle assembly onto the lower boiler; it automatically divides the water between the two boilers. 3. **Dose and tamp**: With the top cup upside down, grind about 20 g of coffee finely into the 53 mm portafilter in its base and tamp it. 4. **Assemble**: Fit the silicone basket cap, flip the top cup over and screw it onto the machine. 5. **Brew on the hob**: Put it on the stove. When the lower boiler reaches 9 bars, the valve opens and about 40 g of espresso brews into the top cup. The **9Barista** is a **stovetop espresso maker** that actually makes espresso. It looks a little like a [moka pot](https://dailyextraction.com/methods/moka-pot/), but inside, a patented **two-boiler** system, designed by a **Cambridge jet engineer**, produces **9 bars of pressure** and brew water at **93°C** on an ordinary hob, with **no pump and no electronics**. The only moving part is a spring-loaded valve. Here's how it works, how to use it, and where it came from. ## The short version - **Two boilers**: one makes the pressure, the other sets the temperature. - **About 9 bars and 93°C**, the espresso standard, on any hob. - **About 20 g of fine coffee** in a 53 mm portafilter, for roughly **40 g** of espresso. - **No pump, no electronics**, one moving part. - **Made in Cambridge, UK**, and designed to be repaired. ## How does the 9Barista work? Daily Coffee News traced the water's journey: 1. **The lower boiler** is sealed. As it heats on the hob, pressure builds until it reaches **9 bars**. 2. At 9 bars, a **calibrated spring-loaded valve** opens and sends super-heated water, at about **179°C**, into a **heat exchanger coiled inside the upper boiler**. 3. **The upper boiler is open to the air** through a small chimney, so its water can't get hotter than **100°C** (at sea level). It cools the brew water to 100°C. You can warm your cups over the steam. 4. A **finned heat exchanger** on the outside cools the water further, to about **93°C**. 5. The water is pushed up through **finely ground, tamped coffee** in a **53 mm** bed, and the espresso collects in the top cup. "The upper boiler uses the property that boiling water open to the air must be at 100°C, at sea level," inventor **Will Playford** told Daily Coffee News. "The pressure and temperature profile are fixed. We wanted to keep the machine as simple and reliable as possible." ## How do you use a 9Barista? 1. **Fill the lower boiler** to the fill line, about **120 ml**. 2. **Screw on the middle section**, which divides the water between the two boilers. 3. **Turn the top cup upside down**: its base is a **53 mm portafilter**. Grind about **20 g** of coffee into it and **tamp**. 4. **Fit the silicone basket cap**, flip the cup and screw it on. (Playford says the cap isn't really needed with a properly fine grind.) 5. **Put it on the hob.** You don't need to adjust the heat; the machine should brew the same way every time, giving about **40 g** of espresso. ![Chart of coffee grind sizes from extra fine to extra coarse, with extra-fine highlighted for the 9Barista](https://dailyextraction.com/diagrams/grind-size.svg#extra-fine "The 9Barista needs an espresso grind, finely ground and tamped.") ## How is it different from a moka pot? | | Moka pot | 9Barista | | --- | --- | --- | | Pressure | About 1 to 2 bars (9Barista's figure) | About 9 bars | | Brew temperature | Not controlled | About 93°C | | Coffee bed | Loose basket | Tamped 53 mm portafilter | | Result | Strong coffee | Espresso | The body is cast **brass**, the seals are standard **metric silicone O-rings**, and there's a **safety valve** that opens at **12 bars**, Daily Coffee News reports. 9Barista says every part is replaceable and that it publishes service guides. ## Who made it? **William Playford** studied jet engineering at the **University of Cambridge**, where his PhD at the **Whittle Laboratory** measured heat transfer in gas turbine engines. The idea came during his PhD, the university's engineering department says: espresso needs high pressure, controlled temperature and precise parts, the same three things as a jet engine. His first sketch dates from **2013**. He used the lab's instruments to measure espresso machines, built and tested dozens of prototypes, and machined some production samples on the Whittle Lab's CNC machines. The company's story adds that he'd been analysing the thermal performance of his own **La Pavoni lever machine** at night in the garden shed. 9Barista launched on **Kickstarter** at the **London Coffee Festival** in **2019**, reached its funding target within **four days**, and raised over **£54,000**, according to Cambridge and Daily Coffee News. The first batch of **170 machines** was due in October 2019. The machine was later named "highly commended" for the most innovative product award at the festival in **2022**, the company says. *General guidance only. The lower boiler is under pressure: never open it while hot, and follow the maker's instructions.* ## 9Barista vs other methods - **[Moka pot](https://dailyextraction.com/methods/moka-pot/):** the classic stovetop coffee maker, at lower pressure. - **[Manual espresso press](https://dailyextraction.com/methods/manual-espresso/):** hand-powered espresso, with a lever or press. - **[Lever espresso](https://dailyextraction.com/methods/lever-espresso/):** spring and direct-lever machines like the La Pavoni. - **[Espresso](https://dailyextraction.com/methods/espresso/):** the full guide to espresso. Explore every pressure method in the [pressure chapter](https://dailyextraction.com/methods/pressure/). ## Words used in this guide - [Portafilter](https://dailyextraction.com/glossary/portafilter/): A portafilter is the handle-and-holder you fill with ground coffee and lock into an espresso machine. - [Tamping](https://dailyextraction.com/glossary/tamping/): Tamping is pressing ground coffee down into a firm, flat, even layer with a tool called a tamper. - [Body](https://dailyextraction.com/glossary/body/): Body is how heavy and textured coffee feels in your mouth, from light and tea-like to thick and syrupy. - [Safety valve](https://dailyextraction.com/glossary/safety-valve/): A safety valve is a small pressure-release valve on the side of a moka pot base. ## FAQs ### Is the 9Barista real espresso? It's designed to be. It brews at about 9 bars and 93°C, the commercial espresso standard. 9Barista notes that a moka pot runs at about 1 to 2 bars, which makes strong coffee rather than espresso. ### Who invented the 9Barista? William Playford, an engineer who did a PhD in jet engine heat transfer at the University of Cambridge's Whittle Laboratory. He first sketched the idea in 2013 and spent about five years developing it. ### Does the 9Barista need electricity? No. It has no electronics and no pump; its only moving part is a spring-loaded valve. The company says it works on any hob. ### How much coffee does the 9Barista use? About 20 g of finely ground coffee in a 53 mm portafilter, which Daily Coffee News says gives a roughly 40 g espresso. ### Can you repair a 9Barista? Yes. The company says every part is replaceable and publishes service guides and spare parts. Daily Coffee News notes the seals are standard metric silicone O-rings. ## Sources - [Alumnus creates the perfect espresso using jet engineering](https://www.eng.cam.ac.uk/node/5113) - [9Barista ushers in a new generation of actual stovetop espresso](https://dailycoffeenews.com/2020/02/13/9barista-ushers-in-a-new-generation-of-actual-stovetop-espresso) - [Our story](https://9barista.com/pages/story)