ne simple pleasure that most of us turn to each day, (which in turn relies on water quality) is our daily Coffee. As a coffee consumer purchasing a home coffee maker, there are numerous factors to consider, some of which impact on energy consumption, price and purity
If you have decided to buy a semi-automatic espresso machine, three important aspects to consider are the Heating Technology, Portafilter, and Grouphead. You can follow this link to read about the best espresso machine for home: without the techno-speak, or read on:
Firstly, we should also talk about the pumps found on espresso machines. In many cases, you will find espresso machines with 15-bar or 18-bar pumps, and these configurations should be rejected. The majority of espresso makers are using a similar stock pump which is made by a company called Ulka. Its vibration pumps are reliable and rarely fail, but their stated maximum pressures are meaningless because quality espressos are best extracted around 8 to 10 bars at the Grouphead. In an Espresso machine, pressure is regulated by an Over Pressure Valve that “bleeds” the water away lowering the pressure, so the 15-bar or 18 bar capacity means little.
That is why some of the semi-commercial espresso machines are now using rotary vane pumps. By using rotary vane pumps rather than vibration pumps, they create less noise in operation, are more robust, and users can control the brew pressure by manually altering the built-in release screw.
HEATING TECHNOLOGIES – Thermoblocks, Single Boilers, Double Boilers and Heat Exchangers
Thermoblocks – are basically a heating component which “flash heats” water. The water is drawn from a cold water chamber and goes through the heated Thermoblock, delivering hot water on demand. Thermoblock steaming is achieved when the temperature is raised even higher on the device and the pump delivers small water bursts which again go through the Thermoblock, and are then released as steam.
The advantage of a Thermoblock is that it can heat up really fast, and remains hot, so the production of steam (and therefore espresso) is rarely limited. A major disadvantage of a Thermoblock system is that the temperature is rather unstable due to the small thermal mass.As a result, the extraction temp from Thermoblock systems can vary, and the steam produced is commonly quite wet as well.
It remains a popular choice for makers of many quality, semi-automatic espresso machines, such as Breville, Cuisine Art, Delonghi, Krups among others.
Many of these brands feature in reviewers lists of the best espresso machines for home:
Single Boilers – are made of aluminum, brass or stainless steel. They serve 2 purposes: namely steam production and espresso extraction. They draw the water from the water reservoir and heat it to a preset temperature. If steam is required, the heating component will heat the water to a higher temperature, and create pressure inside the boiler. Steam will then be released by opening the valve that leads to the steaming wand. All facets are mechanical and there is no need for a pump in the production of steam.
The advantages of a single boiler are temperature stability when extracting espressos, and an improved steamer function resulting from dryer steam. The disadvantage is the down time when switching from the extraction of espresso to producing steam (which is the time needed for the water to boil or cool).
Some examples of espresso machines that feature single boilers are Rancilio, Gaggia and Lelit.
That is all most of us need to know, If you wish you can read more about Double Boilers and Heat Exchangers here: