Hi All, Last week I was invited on a tour of a local coffee farm. While there I purchased 2 packs of freshly dark roasted beans (Arabica). One for my home setup Isomac Millenium and Mazzer Mini grinder and one for work where I have a small Pavoni Lever machine and a noname brand grinder. First grind when I tamped I found very little give in the coffee and when I came to pull he shot on both machines there was no flow. It was like a solid block in the porta filter. I set my grinders coarser and coarser until I eventually got a 25s flow. The coffee came out a muddy colour with no tiger striping.
Then last night my Mazzer grinder slowed down to a dead stop. I stripped it down and found the delivery chute caked solid. Cleaned it out and turfed all the remaining beans. Fresh beans from regular roaster and all is well.

I am intrigued to know if anyone has experienced a similar problem? I have a feeling that possibly the moisture content of the beans was too high, is this possible after dark roasting?

Jay wrote:Hi All, Last week I was invited on a tour of a local coffee farm. While there I purchased 2 packs of freshly dark roasted beans (Arabica). ....... I am intrigued to know if anyone has experienced a similar problem? I have a feeling that possibly the moisture content of the beans was too high, is this possible after dark roasting?

"Dark Roasted" doesn't tell us much. personally, I avoid "dark roasted" coffee. I have often used coffee I home roasted on the day of roasting, or the day after and have no such problems as you described. If the beans you bought were dark and very oily on their surface, that would possibly explain part of your problem in that it was not a moisture problem but an oil problem.

If anything.... the moisture content should be lower from darker roasted beans. Purely speculation on my part but if they are using a water spray quench to halt the roast at end of process AND if the quench was excessive... it could in theory lead to higher moisture content. I'm not saying that's what happened in that case and it should be noted that, properly used, a very brief water spray quench can be useful (especially in air roasters like a Sivetz).

I'm more inclined to think that it's just a problem related to the excessively dark roast level.

Jay wrote:Then last night my Mazzer grinder slowed down to a dead stop. I stripped it down and found the delivery chute caked solid. Cleaned it out and turfed all the remaining beans. Fresh beans from regular roaster and all is well.

Weird, I've never seen a Mazzer choked to a dead stop (I've seen it with the Macap doserless). Maybe dark roasted coffees have a higher oil-to-cellulose ratio, which accounts for their propensity to clog grinders?

another_jim wrote:Excessive water makes sense as a possible cause, since it would have turned the ground coffee into a sludge or cement like a wet puck.

Reminds me of one very early morning a few years back. Out of bed, I headed into the kitchen, more asleep than awake, and was going to top off Silvia's reservoir. Pulled out the pitcher and took the hopper lid off Rocky. Came within about 4 degrees of the pour point from finding Rocky's fluid capacity.

Randy G. wrote:Reminds me of one very early morning a few years back. Out of bed, I headed into the kitchen, more asleep than awake, and was going to top off Silvia's reservoir. Pulled out the pitcher and took the hopper lid off Rocky. Came within about 4 degrees of the pour point from finding Rocky's fluid capacity.

Same here.(different grinder) Glad to know I'm not alone

another_jim wrote:An interesting event.

I actually doubt it's the dark roast alone, since it doesn't happen regularly at Starbucks, or other cafes where the hoppers look like something out of post apocalyptic sci-fi movies.

Excessive water makes sense as a possible cause, since it would have turned the ground coffee into a sludge or cement like a wet puck.

Moisture is my thought as well.
I water spritz (shows ya what reading a Ken Davids book gets ya ) when roasting with my Stir Crazy combo. I overdid it one day with some Brasil. Nearly stopped my Maestro, but the SJ seemed unaffected.
That bean of the OP's must have REALLY bean moist...and oily.

Randy G. wrote:Pulled out the pitcher and took the hopper lid off Rocky. Came within about 4 degrees of the pour point from finding Rocky's fluid capacity.

-sheepish- A few times, I've caught myself almost pouring water into the grinder instead of the water heater. They're right next to each other, and about the same height. I've always managed not to measure out beans into the water heater.

Making coffee before having coffee is quite challenging some days.

Making coffee before having coffee is quite challenging some days.

Quote of the day.. Ill be stealing that for sure