Watch out for rocks

by **mike01** on Wed Mar 10, 2010 7:35 pm

I've heard stories about all the things that end up in green coffee (sticks, rocks, nails, etc). When I home roast, I am sure to throughly check for any stray debris. I have not been doing so so when I buy pro-roasted coffee, because I was under the assumption that most are processing their coffee with de-stoners. Well, I was grinding for my shot last night (using coffee from a roaster well known on this site) and all of a sudden I heard a strange rattling from my SJ. The motor continued to run as normal and I shut it off within a couple seconds. I removed the burr carrier and I found a small metallic rock on the lower burr carrier. It apparently was too large to fit between the burrs and the burrs appeared to be ok. I thought I may have escaped damage to the burrs. However, after reassembling the grinder and pulling a shot, the extraction rate was much faster using the identical setting that I had been using for a couple days without adjustment. I now have to grind about 3 notches finer to get the same extraction time. The shots also lack sweetness and are much more bitter than before. I'm not sure how this can be. I'm guessing a chunk of rock broke off and passed through the burrs, dulling them. I ended up ordering a new set and am now using my mini again, which is a definite improvement over the SJ. The worst part is the burrs were only a few months old and very lightly used. Anyways, I've learned to always check for rocks regardless of where I buy my coffee from.

by **JimG** on Wed Mar 10, 2010 9:22 pm

Last time I bought coffee from my local roaster (and I do mean "last"), the bag contained a 1" long piece of a small hardened nail. It jammed in our Mini E grinder. Fortunately my wife was very alert to the situation and flipped off the power immediately.

The burrs were damaged, but luckily no damage to the motor, bearings, or shaft. Replaced the burrs and all was well.

This particular roaster stores their coffee in publicly accessible, floor level bins which are located all over their shop. Dropping items into the bins could be done very easily by anyone wishing to cause malicious damage. After the nail experience, I began to consider all of the other possibilities with the way their bins are arranged. Haven't been back, and don't plan to.

Jim

by **earlgrey_44** on Wed Mar 10, 2010 11:07 pm

It does indeed happen.

I recently found a concrete chip in a bag of roasted beans from a local roaster. About the thickness of a coffee bean and about two to three "bean widths" across.

by **TimEggers** on Thu Mar 11, 2010 3:07 am

I average about a rock a year.

by **SwingT** on Thu Mar 11, 2010 9:07 am

Umm, well - I'm trying to think of other ways - but at this point the only way I can think of to check your beans is visually.

I've never really done this before.

Any tips on procedure?

by **earlgrey_44** on Thu Mar 11, 2010 9:39 am

This should be counted as one of the advantages of grinding per dose.

It's much easier to see an objectionable object when measuring out 15g's than it is when filling a hopper with x times that much coffee.

by **Jeebs** on Thu Mar 11, 2010 12:17 pm

When I roast I toss my beans between colanders, then pour them on a large pizza pan to finish cooling. I once had a hot rock stick to the plastic colander, and I've found 3 rocks and a few sticks while inspecting the pizza pan. I usually do a quick check for quakers and defects, but with certain origins (esp. Yemen) I also keep an eye out for rocks. Luckily I haven't had one make it to the grinder, and I drink a lot of Yemen.

If I got a rock from a roaster that damaged my grinder I'd probably ask them to replace the burrs, and I think most reputable roasters would.

by **yakster** on Thu Mar 11, 2010 1:43 pm

I suspect with more, smaller artisan roasters out there that the chances of this happening will increase. They probably don't have the equipment that the large commercial concerns do to sort and cull foreign objects and even off-colored beans.

I use two aluminum pans to cull and weigh my beans before and after roast, and sometimes hit them with a UV LED flashlight to look for mold and also other defects as the blacklight seems to provide more contrast making it easier to spot them. Luckily, I only buy commercial beans on occasion and only for espresso generally and since I single dose and hand grind, I see each bean in the tray of my jewelry scale before I grind them up. You could use a magnet to catch any ferrous items, but this is probably a corner case and not all that useful anyway. Certain origins are more likely to have rocks and sticks in them (Tom at Sweet Maria's has posted in his reviews on some coffees to specifically check for these for some beans) but for coffees that have been roasted and stored in bins, it may no longer be origin specific.

I could see if your buying commercially roasted beans taking them out of the bags and pouring them into pans for inspection (I've heard that blue pans are good for culling green beans, not sure if it holds up for roasted beans) and then putting the roasted beans into your storage containers, especially if you put them in jars and store them in the freezer, this would work pretty well as an incoming inspection.

This page talks off all the different foreign objects found post-roast at Caffe Calabria and Bird Rock Roasters:

...after the beans cool, when they pass through the "de-stoner" pan, where staffers pluck out debris that was packed in the raw beans' burlap sacks. Caffe Calabria has found stones, nails, wires, a light bulb's metal base. Once they found a cell phone. Everyone plucks out shriveled or rotten beans, and brass shell casings are common. At La Jolla's Bird Rock Roasters, proprietor Chuck Patton once fished from his
de-stoner one well-done reptile.

You must be doing a heck of a volume not to catch a cell phone pre-roast.

by **networkcrasher** on Mon Mar 15, 2010 11:08 am

yakster wrote:You must be doing a heck of a volume not to catch a cell phone pre-roast.

Either that, or it was Zoolander's cell.. :-)

by **mhoy** on Fri Mar 26, 2010 9:32 pm

I picked something that looked a lot like a rock last week. Didn't try crushing it though.

Mark


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