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I have a Gaggia Classic with Grinder Rancilio Rocky.

Last week, I changed coffee in my grinder, and now, coffee flow is very low.

I had to change 3 level of grinder for my new coffee...

Why Grinder level is coffee bean dependent?

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    Welcome to Coffee! Kindly clarify... 1- When you say "coffee flow is very low", do you mean that the flow of coffee grounds out of the grinder is lower, or that the flow of water through the grounds in the espresso machine is lower? 2- Which way did you change the grinder setting: to a finer setting or coarser setting? 3- What kind of beans (old and new) are you using? For my burr grinder, I find that the flow of darker-roast beans (more oily) makes the grinder work more slowly and that the chute gets clogged more often. If this is your situation, I'll expand to an answer.
    – hoc_age
    Jun 26 '15 at 3:01
  • 1. Water is very low ( for the same grinder setting, it seems light coffee is ground thinner - 2. I had to change 3 level coarser. 3 - I don't know the old bean, but the new bean is fresh! Your explanation make sense! I could accept your answer! A friend told me this bean tastes "darker" ! Jun 26 '15 at 5:22
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Expanding comment into a (possible) answer...

On the topic of different beans in a burr grinder: I find that my (admittedly cheap) burr grinder "chokes" on darker-roast beans. When I put dark roast beans into the grinder, the chute gets clogged with coffee grounds more quickly (as compared to lighter-roasted beans). I have a timer-based auto-shutoff model, and much less grounds come out when the grinder is "clogged" in this way. I attribute this clogging to the oil on the surface of the beans that is somehow "sticky" and more prevalent on darker roast beans, but I'm not certain. This article from Coffee Geek talks about cleaning more frequently for darker roast beans, as does this review from Seattle Coffee Gear, as does this one from Coffee Review.

On the topic of espresso pulled from these grounds: This is tricky and I'm really just speculating. Perhaps it's a similar situation: your darker-roast beans respond to tamping differently than your lighter-roast beans. If you're tamping hard and the grounds are clumping together somehow, you might be getting some channeling (resulting in uneven extraction); this could cause a more "watery" shot. You might be able to see evidence of this in the puck after you pull the shot, or you might be able to see it while pulling the shot if you use a naked (bottomless) portafilter. This article from Home-Barista talks about a too-quick extraction being paired with grind flaws; are you seeing that? It also discusses various other flaws and corrections, too various to summarize here.

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  • Tx for your answer! For the record, I use Espro Tamper, so I always tamper at 30, and I have no problem of channeling Jun 26 '15 at 15:15

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