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I have to wonder how much this static electricity is in an actual coffee shop... I'd think that the machines would be legally required to be electrically earth-

I have to wonder how much this static electricity is in an actual coffee shop... I'd think that the machines would be legally required to be electrically earth-grounded. Wouldn't this remove the static charge as the coffee is physically ground? And, even if the coffee particles are charged after physical grinding, wouldn't water flowing through them in the espresso maker also electrically ground them, thus removing the charge?

lfuller 3y ago
I consult for a specialty coffee shop, and in my experience the electrical ground of the machine has no impact on static generation - I doubt the burrs themselves are grounded. The amount of static you get very much depends on the specific grinder you use. Our large-batch shop grinder creates massive amounts of static and requires water to be added to not end up with a mess, while our espresso grinders tend to generate less. To your second point, one of the fascinating things about this study is that the static charge during the grinding process causes the coffee to clump - that means that by the time the water hits the coffee puck it is too late to avoid the static-induced clumping.
GuB-42 3y ago
On average, what comes out of the grinder is electrically neutral, so there is no more point in grounding the grinder more than for any other electrical device. The problem is at the particle (coffee grind) level, some are positively charged, others are negatively charged. The result is that if two particles of the same charge come close together, both will shoot out in opposite direction, and that direction is not necessarily where your basket is, and it will make a mess. If however, two particles of opposite charge come close together, they will stick together and neutralize, but by doing so, they will form a clump that may cause uneven extraction. The idea with spraying the beans with water is to prevent static buildup before particles have a chance to form clumps or make a mess.

lfuller 3y ago

I consult for a specialty coffee shop, and in my experience the electrical ground of the machine has no impact on static generation - I doubt the burrs themselves are grounded. The amount of static you get very much depends on the specific grinder you use. Our large-batch shop grinder creates massive amounts of static and requires water to be added to not end up with a mess, while our espresso grinders tend to generate less. To your second point, one of the fascinating things about this study is that the static charge during the grinding process causes the coffee to clump - that means that by the time the water hits the coffee puck it is too late to avoid the static-induced clumping.

GuB-42 3y ago

On average, what comes out of the grinder is electrically neutral, so there is no more point in grounding the grinder more than for any other electrical device. The problem is at the particle (coffee grind) level, some are positively charged, others are negatively charged. The result is that if two particles of the same charge come close together, both will shoot out in opposite direction, and that direction is not necessarily where your basket is, and it will make a mess. If however, two particles of opposite charge come close together, they will stick together and neutralize, but by doing so, they will form a clump that may cause uneven extraction. The idea with spraying the beans with water is to prevent static buildup before particles have a chance to form clumps or make a mess.