When you make espresso, you are extracting material from coffee beans based on a measure called solubility, which is the water's ability to extract these materials. The more a bean is roasted, the more its cellulose is broken up, making the flavor materials easily liberated into the water. Consequently, traditional medium-to-dark roasted beans from Italy give up their flavors very easily, which is why historical cafe recipes utilize smaller doses and standard 30-second extraction times. Conversely, lighter roasts are less soluble, meaning they don't give up their material as easily to the water under the same 30-second recipe.
As water pushes through an espresso puck over a 30-second duration, about 20% of the material disappears, causing the puck to become thinner and offer less resistance to the water. For reasons not fully understood, lighter roast beans fall apart and erode much easier than darker roasts. Traditional darker Italian roasts require less concern regarding grinder quality, puck preparation, or high flow rates because the pucks naturally resist water better over time. Light roasts, however, present a dual challenge: figuring out how to maximize water contact time to combat low solubility, while simultaneously keeping the puck from disintegrating and letting water gush through.
If you maintain a flat, constant nine-bar pressure on a medium-to-dark roast, the water speed will accelerate rapidly during the final 5 to 10 seconds because the puck is losing material and resistance, often degrading the flavor. To avoid this, a lever profile mimics historical lever machines by gently raising pressure and then decreasing it. It reduces the pressure at the same rate that the puck loses its structure, honoring its decreased resistance and yielding a better-tasting shot with a wider flavor compass.
The Allonge style is highly recommended for ultralight roasts that feature no roasting-generated flavors like caramelization. Because these beans have incredibly poor solubility and a high tendency to fall apart, the Allonge recipe uses a coarse grind to push a high water flow rate (typically 4 to 4.5 mL per second) straight through the eroding puck. It targets a high ratio of four-to-one or five-to-one of water to beans while maintaining standard espresso pressures of six to ten bar at its peak. This high-volume, rapid approach effectively addresses the low solubility of ultralight beans without turning the shot into an unpleasantly acidic, low-pressure gusher.
Blooming is an excellent go-to recipe for intermediate, specialty light-to-medium-light roasts that feature subtle fruit or floral notes. It serves as a compromise between the high-flow Allonge and a traditional lever shot. To overcome low solubility, the blooming recipe introduces water into the puck and then pauses entirely for 30 seconds, giving the beans time to give up their material to the water before completing the espresso extraction. While its total run time of roughly 72 seconds makes it too slow for busy cafes, it is ideal for home users because it preserves the thick concentration, crema, and classic two-and-a-half-to-one or three-to-one ratio of a traditional espresso.
Darker-than-medium roasts often bring out unpleasant burn notes, bitter tannins, or oily characteristics. To hide these flaws and emphasize a thick, concentrated chocolate profile, you should utilize shorter extraction ratios (such as 15 grams in to 26–28 grams out) and grind the coffee much finer to slow the shot down to around 40 to 45 seconds. Using a classic lever profile instead of a flat nine-bar profile for these shots will also prevent unpleasant acidity at the end of the extraction.
New owners of advanced espresso machines like the Decent will initially experience issues with bad puck preparation because they aren't used to a machine that provides active feedback. Beginners should initially strive for shorter water-to-coffee ratios—such as pulling 30 to 32 grams of liquid from a 15-gram dose—rather than trying to push for longer, advanced extractions like a 42-gram yield. As puck preparation skills and grinder quality improve over time, users can gradually grind coarser and extend their extraction ratios safely.