Cheap Coffee Beans and Grinder Static

May 23, 2022 6:10 PM

Grinding beans in my burr grinder causes a lot of static so that the grounds fly everywhere - but only if I buy cheap beans. Why?

When I use cheap (e.g. President's Choice) coffee beans, the ground coffee comes out full of static electricity and I get coffee grounds all over my kitchen counter. But if I buy more expensive (e.g. Kicking Horse) beans, there's no static at all. What's the explanation here? Why are fancier beans less electric?

posted by Prunesquallor to Food & Drink (15 answers total)

My guess is that the cheap coffee is not as oily. The fancy coffee I get looks shinier to me and the cheap coffee beans look dry. The oil would obviously help to keep down any explosive coffee dust.
posted by RobinofFrocksley at 6:14 PM on May 23, 2022 [10 favorites]

My theory on this is that the cheaper beans contain less moisture than the fancy ones. I have this problem with darker roasts but not with my preferred light-medium roast. One way to check this would be to compare the volume for the same weight of beans.
posted by fedward at 6:25 PM on May 23, 2022 [2 favorites]

If you're curious, Cook's Illustrated tried a few trucks that are reputed to help get rid of coffee grinder static and found that the best method is just to wait a few minutes after grinding before opening up the receptacle for the grounds.
posted by Johnny Assay at 6:31 PM on May 23, 2022 [5 favorites]

+1 on RobinofFrocksley, though I don't think it's the expensiveness. I buy pretty expensive medium roast coffee and the same thing happens to me. When you lightly roast the beans, the oil isn't extracted from the bean as much. The darker roast coffee is just more oily.

My own way of dealing with this is to tap the side of my grinder a minute or so after it finishes. Then pull out the grounds receptacle, shaking it gently from side to side and tilting it to ride up along the side. I have some vague memory of high school science where that helped the spare electrons creating the static restabilize with whatever material they'd popped off of. I do this, and the grounds "calm down," responding to gravity and settles at the bottom. It's easier to dump it into the coffeemaker after that.
posted by SoundInhabitant at 6:44 PM on May 23, 2022

The so-called Ross Droplet Technique (or RDT) is a somewhat silly way of saying "spray your beans with a little water before grinding." Because water is a polar substance, this will bind to extra electrons and prevent static. I use a tiny little misting bottle and find that about one spray per 10g of beans eliminates static altogether.

As to what's causing it: generally, darker roasts are more prone to static, because they've had more moisture driven off of them during the roasting process. Cheaper brands tend to roast darker as that covers up imperfections in the underlying beans (at the expense of not being able to taste the subtle flavors prized in the specialty coffee community). That might account for what you're seeing. Also, the older the bean, the more likely they are to have driven off various volatile organic compounds. My bet is that your fancier beans are closer to their roast date and thus are less stale and less prone to static.

If you're interested, you can check out the ... extensive ... home-barista threads on the topic.
posted by kdar at 6:57 PM on May 23, 2022 [8 favorites]

+1 on RobinofFrocksley, though I don't think it's the expensiveness. I buy pretty expensive medium roast coffee and the same thing happens to me. When you lightly roast the beans, the oil isn't extracted from the bean as much. The darker roast coffee is just more oily.

Another +1 to this. I use very expensive beans (pricier, apparently, than Kicking Horse, but not like limited Geisha varietals usually), typically light to medium roast, roasted in the past week, and have hellacious problems with chaff going everywhere. I actually called Baratza USA and discussed it with them, and the response was super friendly and basically "no we haven't been able to solve it either, but here are some things to try" and nothing has really worked.

My solution? A brush to wipe down the grinder and a decorative tray underneath that I can periodically empty.
posted by Special Agent Dale Cooper at 7:07 PM on May 23, 2022 [3 favorites]

I see this with beans of various levels of expensive- the less oily, the more static. I sprinkle a few drops of water on my beans before grinding (just run my fingers under the tap briefly and flick a few drops after I pour the beans in) and it works for me!
posted by MadamM at 7:12 PM on May 23, 2022

I buy fancy-ish fair trade beans at my local Coop and haven't encountered this problem. I add a bit of ground salt, cinnamon and cocoa to the grinder with the beans but don't know how that would impact the static effect.
posted by Scout405 at 7:58 PM on May 23, 2022

I had a cheap ass Capresso burr grinder that threw grounds everywhere. Replaced it with an OXO burr grinder (with a low static stainless steel container) and now have almost zero fines.
posted by cyndigo at 8:08 PM on May 23, 2022

All burr grinders generate static, they just have more or less mitigation built in. RDT is “the” way to get rid of it, even on grinders that claim to be grounded. Grinders that don’t have apparent static are either generating less, usually by spinning at lower RPMs (I assume we’re not talking in the 2k+ range of variable speed large-flat-burr single-dosing grinders), or by hiding it from you by putting a chute of some sort between the burr chamber and the grounds outlet. There, the grounds are allowed to clump and stick to each other instead of flying away, or just stick to the inside of doserless funnels that look like this.

I agree that it seems likely that very stale beans would have more static than fresher beans due to moisture content. There’s also pre-roast aging of the green, where I can imagine cheap beans being less meticulously controlled for humidity.

I don’t have a good sense of how roast level would impact static; I haven’t ground an oily bean in years, thank goodness. Origin probably has an effect, and altitude (which positively affects density).
posted by supercres at 8:33 PM on May 23, 2022

(Personally, I live with it on my single-dose grinder. I RDT each dose with a small mist bottle and brush out the hopper and use a bellows every time, with a dose of compressed air in the chute about once a day. I updose by about 0.7g, depending on the bean, but I have put tracked what kinds of beans need more or less “extra”.)
posted by supercres at 8:35 PM on May 23, 2022

Cheaper beans may be heavily roasted then also held before sale for a long time so there's even less moisture. I've taken, like many here, to getting a few droplets of water into the beans in the hopper before grinding -- though I wonder why can't the metal burrs themselves be grounded to eliminate this static charge?
posted by k3ninho at 3:38 AM on May 24, 2022

kdar and supercres have it. RDT is the way to go. It's also worth noting that different grinders have better or worse ways of dealing with this issue through a combination of design and materials. I have a Niche Zero, which is probably the most economical single-dosing grinder with retention below 0.2g on average, although it is by no means inexpensive. I haven't experienced any static issues but other Niche Zero owners, particularly those living in dry climates, seem to have quite a few static issues on coarse grinds.
posted by slkinsey at 7:54 AM on May 24, 2022 [1 favorite]

Another data point. In my (grudgingly) "French Roast" household, my Baratza Sette 270i grinder (what was I thinking?) generates static-y grounds sometimes, sometimes not. But one factor that helps is waiting some seconds after the grinding completes. The static charge can dissipate somewhat over time. Then, tap the grounds container a couple of times to help it along.

This problem can be worse with lighter-roast beans, though the grinder is less likely to clog with those lighter roast beans.

Question for Baratza: does RDT introduce destructive moisture into the grinder?
posted by Citizen Cane Juice at 5:05 PM on May 24, 2022

The amount of moisture in RDT is incredibly minute. Think the amount that would be in one short spray from a little perfume bottle. I have done it by running water over my finger, shaking it off and then swirling my barely damp finger in the beans just prior to grinding.
posted by slkinsey at 8:45 PM on May 24, 2022