Why Doesn’t the Coffee Bed Swell During Blooming in Pour-Over Brewing?
Whenever I brew a pour-over for a customer, if the coffee bed balloons noticeably during the bloom phase, there’s a good chance someone will ask: “Why doesn’t my coffee bed swell up like that when I brew at home?” This is actually one of my favorite topics to discuss. Strictly speaking, the size of the bloom doesn’t directly reflect how the coffee will taste. But it does reveal a lot of other information — such as the condition of the beans and the brewing parameters used. These factors are precisely what determine how much the coffee bed puffs up. So today, let’s break down how these factors affect the size of the bloom — and why, in the end, a bigger bloom doesn’t necessarily mean better coffee. 1. Bean Freshness and Roast Level First, we need to understand why the bloom happens. The main reason is carbon dioxide (CO₂) . During roasting, coffee beans accumulate a large amount of CO₂, which is slowly released after roasting. When the ground coffee comes into contact with h...