When it comes to brewing espresso precision and consistency is key. Once you’ve dialed in the ratios and temperatures that you think best suit your equipment and desired brew method, you want to know that you can keep replicating them.
Among the variables to be controlled for is brewing temp. Too cool and the shot you pull will be weak and underdeveloped, too hot and you risk over-extracting the beans and bringing forward less pleasant notes. Just how well you’ll be able to control your water temperature and the types of drinks you can make comes down to the type of heating element you are using. For most home coffee systems water is heated with a single, twin or heat exchanger boiler.
Single boilers, as the name would suggest, have one boiler. This means that they’re capable of heating one source of liquid to your desired temperature. It also means that they might not be ideal for cappuccino or latte lovers as the system means it isn’t possible to steam milk while pulling shots. There are single boiler systems that come with steamer attachments, they just typically require the user to flip a switch to change where the heat is sent. Single boilers are usually recommended as a great option for those who are primarily interesting in drinking straight espresso.
Double boilers, while more expensive, can allow for a little more versatility of application. Multiple boilers allow one boiler to keep water at temperature while the other produces steam. The double boiler system can also be a must have for people wanting to make multiple drinks at a time. With a single boiler, the water will continue cooling for however long it takes you to froth your milk making it so you will have to reheat the water before pulling another shot. This isn’t a problem a problem with double boiler systems as the one boiler remains able to maintain the water’s temperature, allowing you to pull multiple shots back to back while creating latte art to your heart’s content.
Heat exchanger systems have a single boiler heating the water container. Cold water is then pumped through in a separate tube within the main boiler. That water is heated and pumped out to be used for making espresso, typically after being combined with cool water in order to achieve the desired temperature. This is because the water in the main boiler section is usually far too hot for espresso, a design feature that allows it to be used for creating steam. Heat exchanger systems are therefore able to have the functionality of a double boiler, with one less heating element.
Thermoblocks are a less conventional option, but one that can often be found in low-cost all-in-one systems. They work by channeling water through a narrow pipe within a metal block that is heated to the desired temperature, which in turn heats the water,before piping it to where it’s needed for brewing. This method has the advantage of only needing to heat small amounts of water at a time and can sometimes be quicker and more energy efficient than traditional methods. However, there is a downside that comes with thermoblocks’ reliance on narrow pipes and less expensive materials. They typically use aluminum pipes which are more prone to scaling issues. Using aluminum on its own isn’t necessarily bad, the material is better than the frequently used brass at retaining heat (but worse at making steam). The problem arises from being combined with the narrow form factor of the thermoblock, meaning that even small amounts of sediment can clog the system. Thermoblocks reliability can vary wildly depending on their materials and build quality, but the upkeep needed and potential longevity issues can make them an unwise investment for many.
When you’re looking to buy a coffee or espresso maker, it’s tempting to get drawn in by convenience features and design. But if these things aren’t supported by quality materials and build, you may not get the quality of coffee or longevity of use that you think you’re paying for. For most people, a single or double boiler will give you the best combination of versatility and quality. Their ability to produce steam and hot water, as well as their superior reliability, mean that an investment in one is a far less risky proposition than a similar thermoblock system. Hopefully, understanding the kinds of heating implements availableon the market and the features they offer will give you a better idea of which is the right choice for you.