Going against conventional wisdom, researchers at the University of Portsmouth in the UK say the way to consistently make better espresso is by using fewer beans and grinding them more coarsely, reports Interesting Engineering:
"When beans were ground finely, the particles were so small that in some regions of the bed they clogged up the space where the water should be flowing," Dr. Foster said in a press release announcing the research. "These clogged sections of the bed are wasted because the water cannot flow through them and access that tasty coffee that you want in your cup. If we grind a bit coarser, we can access the whole bed and have a more efficient extraction. It's also cheaper, because when the grind setting is changed, we can use fewer beans and be kinder to the environment. Once we found a way to make shots efficiently, we realised that as well as making coffee shots that stayed reliably the same, we were using less coffee."