A simple trick to make better coffee: cut the static!


You’d think that coffee afficionados had tried everything by now, and that few if any tricks remained undiscovered. Well, you could be right–but there’s one trick that most ordinary coffee drinkers probably don’t know, and it’s remarkably easy to do.

I’ll jump right to the punchline, and then I’ll explain the (new) science that explains it. To make richer coffee in the morning, simply spritz a little water on your beans before grinding them. That’s it!

So what happens when you do this, and why does it make better coffee? Well, as explained in this new paper in the journal Matter, by Christopher Hendon and colleagues at the University of Oregon, it’s all about reducing the static electricity that the grinding process creates.

Grinding coffee causes triboelectrification. If you’ve never heard of that, not to worry–neither had I, until I read the paper. Basically, when the beans rub together, they create static, and that makes the ground coffee clump together (and sometimes fly into the air).

Then when you make the coffee, the clumping means that the water flows through the grounds unevenly, absorbing less of the coffee particles than it might. Ideally, all the coffee grounds should be evenly and densely packed, and static electricity prevents that.

Water reduces triboelectrification quite a bit, it turns out.

So what happens? Well, after extensive experimentation–and I do mean extensive–the scientists found that the amount of coffee solids in a cup of espresso increased from 8.2% to 8.9% when adding a bit of water to the beans before grinding. That’s a relative increase of 8.5%. Richer coffee!

Reading the paper, I realized these scientists had a lot of fun doing these experiments. They measured the water content in 31 types of coffees, and tried a wide range of settings for their grinders, for the water temperature, and more.

They also roasted their own beans to varying degrees of darkness. They tried dozens of combinations of beans and roasting strategies, measuring the water content after roasting and the amount of static electricity generated upon grinding. They observed that darker roast coffees usually generate finer ground particles, and finer particles in turn generate more static electricity.

They drank a lot of coffee to get this right! But hey, sometimes science requires sacrifices, right?

I should mention that the trick of adding a little water to the beans is already known to some experts, although the precise science behind it was unknown until now. It even has a name (as the paper points out): the “Ross Droplet Technique.”

As the paper concludes, “a few simple squirts of water [may] have solved the problems of clumping, channeling, and poor extractions while aiding in the pursuit of attaining the tastiest espresso.” You only need a few drops of water–give it a try.

One important caveat is that if you use the French press method to make coffee, where the grounds are immersed in water, then this trick won’t make any difference.

What’s next? Well, I should point out that this study focused entirely on espresso. Does it work for regular coffee as well? Probably so, but more research is needed.