A dual boiler espresso machine has two independent boilers, one to brew the espresso and the other to provide steam for frothing the milk. Current models typically have a digital control on the brewing temperature mechanism, allowing precise temperature adjustment for different kinds of coffee.
The dual boiler espresso machine addresses two fundamental facts about espresso:
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You Need Two Different Temperatures
The first of these is that two widely differing temperatures are required for making espresso and steaming milk.
The milk froth on top is an indispensable part of the beverage, and getting it right requires high-temperature steam to produce the foaming effect. However, coffee lovers will agree that the best temperature for brewing the beans is much lower, in the vicinity of 200 degrees F. The difference in optimal temperatures is so great that separate heating is required for the two elements of the drink.
The Temperature Needs to be Optimal
The second fact is that for every kind of coffee, there is an optimal temperature for extracting flavor. For those who wish to obtain the full experience of espresso, this detail is crucial. A change of coffee often requires a change of temperature, and very small adjustments can make a difference. This means that the more precise the temperature control, the better the cup of espresso.
What Are Your Options?
Among the manufacturers of espresso makers, these issues have been dealt with in three ways.
Single Boiler System
The most basic design is the single boiler system in which the coffee is brewed in a chamber and poured out, after which the same chamber is used to heat water to steam temperature for frothing the milk.
If more than one cup is needed, there is an inevitable delay while the temperature adjusts. Since espresso is usually prepared in social or commercial settings where more than one person must be served, single boiler machines are often hopelessly slow.
Heat Exchange Machine
Another way of dealing with the issues of espresso making is the heat exchanger machine which are commonly found in home bean to cup coffee machines.
In this design, there is one chamber in which water is heated to steam temperature for the milk froth. A metal tube runs through the water carrying a separate supply of water for brewing the coffee. Since the water moves through the tube very quickly, it is only heated to about 200 degrees F.
At this temperature, it will make coffee, but what is missing is the crucial fine tuning ability needed to achieve the optimal brew temperature for each kind of coffee.
The concept of individual brewing for maximum flavor and aroma is fundamental to espresso making, so the heat exchanger design will always be lacking something.
Dual Boiler System
The best design for the serious espresso lover is the dual boiler system, which solves the problem by providing two heating chambers.
Since there is no connection between the two other than the pump head, brewed coffee and milk foam can be produced at the same time with no delay for adjustment. For parties or commercial locations where many drinks must be prepared quickly, this is the ideal design.
Dual boiler espresso machines also have digital controls for brewing temperature, permitting that essential element of precision required for espresso. If one changes to a new kind of coffee, the temperature adjustment is simple and quick.
The advantage of a dual boiler is that it is the only unit commercially available that delivers the true espresso experience with a minimum of wait and trouble. At a party, it ensures that no one will be left waiting for the milk to froth when everybody else is finished. In a commercial location, it gives quick service and keeps the customers happy. Wherever it is used, it is obviously the superior design.