NYC_Crema Senior Member Joined: 13 Oct 2004 Posts: 1,493 Location: New York City Expertise: I love coffee
Espresso: Miss Silvia Grinder: Mazzer Mini Roaster: I <3 Gorilla Coffee
Posted Wed Dec 29, 2004, 8:41am Subject: How does a ROCK get into a GRINDER?
I've read a few posts on how their grinder was ruined by a rock. How is this possible? How does a rock get into a grinder? I ask this because I want to make sure this doesn't happen to me. I can't really see how it is possible a rock can make its way into the grinder. I guess a rock could tag along in those huge burlap coffee bags and then into your 1lb bag to take home...
For those that have had this problem, please share, so the rest of us can know what to look for. I'd cry if my new Mazzer meet a rock.
Fred_Astaire Senior Member Joined: 18 Jan 2003 Posts: 174 Location: NY/NJ Expertise: I love coffee
Espresso: Isomac Tea Grinder: Solis Maestro; NS MCF Vac Pot: none Drip: Braun (love my drip) Roaster: Hottop
Posted Wed Dec 29, 2004, 8:46am Subject: Re: How does a ROCK get into a GRINDER?
If you home roast, you can sometimes find a small stone or two in a bag of green beans. It's pretty rare in my experience, but I've had a few. The stones can go unnoticed through the roasting process, right into the grinder. If you don't home roast I wouldn't worry about it.
Posted Wed Dec 29, 2004, 9:26am Subject: Re: How does a ROCK get into a GRINDER?
Fred_Astaire Said:
If you home roast, you can sometimes find a small stone or two in a bag of green beans. It's pretty rare in my experience, but I've had a few. The stones can go unnoticed through the roasting process, right into the grinder. If you don't home roast I wouldn't worry about it.
I doubt that home roasting makes this any more likely. I inspect my home roast -- I doubt anyone visually inspects commercially roasted coffee as closely as most home roasters do.
Posted Wed Dec 29, 2004, 9:32am Subject: Re: How does a ROCK get into a GRINDER?
Do a search in any home roasting coffee forum for rocks or foreign objects in greens, you will see it does happen. There is a thread at greencoffee.coop about different objects people have found in greens. I too find it a little difficult to imagine it passing by me as I home roast, but I have never done 5lb batches. I think there would be a higher chance of it going by me if I did bigger batches. I have only heard about it in homeroasting, although I don't doubt it could happen in commercial roasts as well.
brugeswalker Senior Member Joined: 15 Jan 2003 Posts: 145 Location: Delaware Expertise: I love coffee
Espresso: Expobar Pulser Grinder: Cunill Tranquilo SS Drip: Only in the office :-( Roaster: Thinking about it
Posted Wed Dec 29, 2004, 9:39am Subject: Re: How does a ROCK get into a GRINDER?
Coffee break time!
I had the unfortunate experience of getting not just a rock but a BOULDER in my grinder a couple of weeks ago. It locked up the burr set, perhaps bouncing around there for a while getting polished before shutting down the machine. I never ate dirt as a kid, but as an adult I now get my mineral supplements through my espresso intake. ;-)))
My personal rock was large ( approx. 3/4" X 1/2" and irregularly cylindrical) and, perhaps most importantly, not very heavy.
The fact is that coffee is not a very clean product. You can expect to get twigs, stems, leaves, dust, dirt, and yes, the rare boulder intermixed with those beans.
If you buy ground coffee you will likely never notice impurities, they will be as fine as the grind and intermixed. Brew and enjoy the earthy flavor!
If you buy roasted whole beans, you will still find debris intermixed, but it will not be particularly common. However, what is there will be hard to detect because it will inevitably be the same color as the roasted beans.
If you buy green beans, you are likely to find more stuff and be better able to identify what doesn't belong there. Rocks, twigs, etc. will be a different color, shape, etc. than the beans. If you are buying a blended bean selection, it may be more difficult to pick out debris because it will be mixed in with various shades of raw beans.
Raw coffee off the plantation does go through some rough cleaning, but, as with any agricultural product that is hand harvested, extra stuff is gathered in. The harvested coffee is then often spread on concrete or stone drying platforms, and this is where your rocks may creep in. Once the raw coffee is bagged and shipped, it may get a bit of a dusting through the commonly used raw burlap.
The most effective cleaning often occurs at the commercial roastery. If you buy raw coffee to roast yourself, you are pretty much responsible for this cleaning stage. The commercial roasters may or may not use a conveyer belt that passes the beans over a blower. The dried beans are light and they get blown up, while the heavier debris, like rocks, gets left behind. The blowing action may also blow off dust and twigs, but unless there is a second stage blower or filtration mechanism, that light debris may just settle back in among the beans. There is also a constant visual monitoring of the beans but as anyone who has stared at a conveyer belt for long can attest, it is easy for small items to pass by. There may also be a sieve type mechanism that allows the smaller beans to get through, while holding back boulders and twigs.
How to avoid the boulder in the grinder problem? Simply examine all the whole bean coffee you use. A slow pour into the hopper will usually reveal garbage. I usually stir the poured coffee beans as well to see what separates out.
How did that miscreant rock get into my grinder? I had a 1/4 bag of coffee remaining and in my rush one morning I just dumped it in without looking. In my own defense, that rock was stained the same color as the dark roasted beans I was using, so it is possible that even if I were looking for it I would have missed it.
I was lucky in that there seems to be no damage to the grinder - got to love that heavy duty Cunill build! If your grinder stops grinding all of a sudden - stop and take it apart to find out if you might have a rock jammed in the burrs. No reason to continue to strain the motor and possibly damage the burr set by trying to force garbage through.
My final point is that despite everyone's good effort, the rare rock or twig will get through. You minimize your chance for an early grinder death by making sure you have a heavy duty grinder to begin with - those large commercial grinders take a lickin and keep on tickin, same for the semi-pro units by the likes of Cunill, Rancilio, Mazzer, Macap. Lighter duty machines with softer metal burrs, plastic collars, weak motors will suffer significantly more damage and require repair or replacement. I guess this is one more reason to spend the money for a good grinder up front, rather than after the "bargain" has died.
default Senior Member Joined: 1 Jun 2004 Posts: 247 Location: bkk Expertise: I live coffee
Espresso: Dalla Corte Mini Grinder: Anfim Caimano Vac Pot: Hario Drip: Hario Roaster: Gene Cafe
Posted Wed Dec 29, 2004, 9:43am Subject: Re: How does a ROCK get into a GRINDER?
i've got it once, the burr stopped, and i quickly switch off the grinder. i removed it to find a small, bean size, stone, resulting in one blade of the lower burr got small dent. should that yeild problem in grinding? should i change my grinder? (i'm eyeing on mini or cimbali jr)
so i believe it's possible when buy lower grade beans from the roaster because they roast larger batch and it's hard to sort that culprit out. my solution is to look for it while i scoop the beans out to the hopper. in smaller amount it's easier to see.
Posted Wed Dec 29, 2004, 9:55am Subject: Re: How does a ROCK get into a GRINDER?
I have visions of the urban legend regarding the scuba man found dead in a tree. (Supposedly scouped up by one of those big helicopter buckets used to put out fires; CSI episode anyone) Any creative ways for a rock to get into the grinder rather than less than perfect quality control at the supermarkets? Maybe a renagade hamster or kitten destined to ruin you mornings and take over the world? A pinky and the brain plot idea perhaps?
DEchelbarger Senior Member Joined: 12 Feb 2004 Posts: 416 Location: Negaunee, MI Expertise: I live coffee
Espresso: Solis SL-70 Grinder: Macap M 4, Rocky,... Vac Pot: Bodum Santos, Nicro Drip: pour over, Chemex, FR Press,... Roaster: RK Drum, I-roast, manual...
Posted Wed Dec 29, 2004, 10:24am Subject: Re: How does a ROCK get into a GRINDER?
I have found a number of stones in Yemen -- yes, I look for them post roast; and one in Harar. Dry Process I think is a higher risk -- should say these are very high grade coffees. Just keep your eyes open.
Posted Wed Dec 29, 2004, 2:15pm Subject: Re: How does a ROCK get into a GRINDER?
I roast in 1lb or less batches, so it's obviously a lot easier for me to identify such stowaways. I too look when I'm scooping the beans into the hopper as well. I've been lucky so far! I don't know what I'd do if my poor Mini's burrs were compromised...
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