The short answer is this is likely an electricity issue. When coffee beans are ground against metal burrs (we've even seen it with ceramic burrs) they pick up a minor electric charge. No, the amount of static electricity on the ground coffee is not enough to shock you or damage the grinder. Instead, it’s just enough to annoy you. When you pull out your “ground coffee chamber” and find your counter, floor, portafilter, and so-on sprayed with a fine mist of static-y coffee dust. Then, when you go to empty your grounds-holder it leaves behind 1-2 percent of your coffee weight as it clings to the side of the chamber.
Some coffee grinders do have a metal chamber, and we have seen this help with the issue. Metal is much more effective at conducting electricity and less likely to “insulate” the bits of ground coffee and prevents them from keeping their charge.
Generally, the coffee grinder itself gets blamed for causing the static mess that people encounter (because the whole beans showed no signs of static), but the same grinder, in the same room, at the same time, with different beans can show no signs of static, so is the fault that of the beans? There are myriad workarounds shared by many to minimize or eliminate this messy problem. Probably the most universally effective is to momentarily increase the humidity of the whole beans just prior to grinding (this is fancy talk for spray a LITTLE water mist or droplets on them). Obviously, this only works if you have a small number of beans in your hopper, or else the beans on the bottom get no water.
In summary, grinding coffee beans is an activity that occurs in a system made up of numerous uncontrolled variables (varieties of beans, degree of roast, freshness, humidity, temperature, and so-on). With the best grinder technology and some variables in your favor, you will have minimal to no static issues. If a few too many of these variables stack up against you, then you are bound to see a static-ee mess, to some degree. When you encounter static, we encourage you to wait 15-30 seconds after the grind has completed allowing the charge to bleed away, then tap the side of the bin and all the grounds should fall into the bin. Good luck!
