The Bloom

One way of improving extraction in a “percolation” method (one where the water becomes coffee and comes through the other side without stopping) is to add a bloom phase. Blooming is a pause at the beginning of brewing, after adding a small percentage of the water that will be used for brewing, typically 1-3 times the weight of the grounds. The intent of this is to get all of the grounds wet without much water dripping through.

The reason for the bloom is that when coffee, particularly if it is fresh, is dampened, carbon dioxide that is in the beans will start to come out. You will often see coffee bubbling or inflating into a pillow of coffee and air. This is a good sign (of freshness), but it makes it really difficult to extract anything from the coffee beans. If you add water too quickly, a lot of water will pass through the coffee bed without extracting very much and your overall brew will either be under-extracted or watery.