In 2018, we came across the first espresso machines with thin-film heaters. Meanwhile, thin-film heater technology, known as Flow Through Heater (FTH), Fast Through Heater, or ThermoJet, has arrived in the espresso machine and Kaffeemacher market. Thin-film heaters have not only surpassed the classic thermoblock in terms of performance and flexibility, but are increasingly putting pressure on manufacturers of traditional espresso machines with boilers.
In 2018, we tested the Sage Bambino from Australian manufacturer Breville, which operates in Europe under the name Sage Appliances. The machine was impressively fast at reaching temperature, but left something to be desired in terms of temperature consistency. Shortly thereafter, the Sage Barista Pro also landed on our test bench, and by then it was clear: the potential of thin-film heaters is enormous.
Both machines were equipped with a thin-film heater from Dutch company Ferro Techniek. While Sage introduced its thin-film heaters with the trendy marketing name "ThermoJet", the heating elements are called Flow Through Heaters by the manufacturer itself. How the Flow Through Heater works, which machines it now appears in, and what this means for the market is the subject of this article.
Maro, Zuriga, Sage and Co.
What do Maro, Zuriga Generation 2, and Unica have in common with Sage Bambino and Sage Barista Pro? They share a heating technology: the thin-film heater. And they're in good company. The Tone filter coffee machine, the Aiden Precision Coffee Maker, and the ETNA milk system also rely on thin-film heaters. The roster of manufacturers using thin-film heaters from Ferro will soon be expanded by two more innovative espresso machines: Roxy Espresso and nunc.
What an amazing success story the Dutch company from Gaanderen in Gelderland can boast. The company specializes in thick-film heating elements printed on metal substrates and offers customized solutions for various industries. Ferro is part of the Otter Control Group and operates production facilities in the Netherlands, Hungary, the United Kingdom, and China. Around 50 employees work at the headquarters in Gaanderen, with another 80 in Budapest at Ferro Electronics. The Otter Group employs approximately 1,500 people worldwide.
The history of Ferro's Flow Through Heater gained momentum in 2013. The manufacturer put together a "developer kit" containing everything needed to build prototype applications. Part of the kit, in addition to the FTH MK2, was a pump, a flow meter, and a control board. This kit was ordered by around 100 companies.
Interestingly, Ferro had already developed an older version of the FTH, the so-called "FTH MK1", back in 2007. However, this could handle a maximum of 2.5 bar of pressure and was therefore used in machines with pads. Espresso brewing requires pressure standards of up to 15 bar depending on the pump.
The "FTH MK2", which is suitable for espresso and can also generate steam for frothing milk, was completed in 2010 as a proof of principle. FTH production was then ramped up in 2015, with Sage/Breville being central to the success story of thin-film heaters as a first mover.
What are the strengths of thin-film heaters?
Thin-film heaters have significant advantages over boiler and thermoblock systems:
How do thin-film heaters work?
The water to be heated flows through a flat channel that is directly integrated into the substrate of the thin-film heater. This channel is designed to optimize water flow and maximize heat transfer.
| Component | Design Detail |
|---|---|
| Material | The channel typically consists of the same material as the substrate (usually stainless steel). |
| Shape & Geometry | Tubular or branched geometries to create targeted turbulence for optimal heating. |
| Manufacturing | Deep drawing and special joining processes to seamlessly integrate into the heating element. |
| Pressure resistance | Designed for the espresso pressure range of up to 15 bar (MK2 generation). |
By directly integrating the channel into the FTH substrate, immediate and highly efficient heat transfer from the printed resistance element to the flowing water is ensured.
Temperature sensor integration and control
The flat design and fast reaction time require highly precise sensor technology and control systems. With little thermal mass available for buffering, the control must adjust in real time:
Modern FTH systems use microcontrollers that reconcile values in the millisecond range:
Different systems, different FTHs
Depending on the application, different FTH models from Ferro are used:
| Machine system | Installed thin-film heater | Application area |
|---|---|---|
| Maro Model 1 | FTH II 2300 W | Maximum performance for flow & steam |
| Sage Bambino | FTH II 1500 W / 2300 W | Compact household ThermoJet |
| Zuriga E2 Gen 2 | FTH II 1400 W + 600 W brew group | Separate heating for water/steam & group |
Challenges and future prospects
Precise FTH control is one of the biggest challenges: without buffering thermal mass, inaccurate control loops immediately cause temperature fluctuations. The difficulty of integration became apparent in early Sage/Breville models. While earlier generations still showed fluctuations, the continued development demonstrates the enormous potential.
Manufacturers like Zuriga and Maro impressively demonstrate the performance inherent in this technology. The thin-film heater flexibly handles all tasks: heating brew water, generating steam, and heating the brew group and portafilter.
With the thin-film heater, a new era has begun in the espresso machine market. Especially in the home segment, the FTH offers almost exclusively advantages over classic boiler systems: it heats up in minutes, saves massive amounts of energy, and allows precise temperature profiles.
First applications are also coming to the commercial sector. Manufacturers like Tone are already working on commercial concepts with thin-film heaters, and durability tests with the Maro show excellent temperature consistency even under high frequency use.
Overview: Machines with thin-film heaters
| Year of release | Machine / Model | Features / Heating element |
|---|---|---|
| 2018 | Sage / Breville Bambino Plus | FTH II 2300W ("ThermoJet") |
| 2019 | Sage / Breville Bambino | FTH II 2300W |
| 2020 | Sage / Breville Barista Pro | FTH ThermoJet System |
| 2021 | Sage / Breville Barista Touch | FTH ThermoJet System |
| 2022 | Unica Pro | FTH II 1800W |
| 2022 / 2023 | Tone filter coffee machine | Commercial through-flow heater FTH |
| 2024 | Maro Model 1 | FTH II 2300W – High precision |
| 2024 | Zuriga Generation 2 (E2) | FTH II 1400W + 600W group heating |
| 2024 | Sage / Breville Oracle Jet | ThermoJet dual system |
| 2024 | Aiden Precision Coffee Maker | Precision filter coffee machine |
| In development | Roxy Espresso | Compact portafilter with FTH |
| In development | nunc. coffee | Smart espresso system |
| In development | datum.coffee | Innovation project |
| Other systems | ETNA milk system | FTH for milk heating |
