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Thanks to all who have taken their precious time to reply and enlightened this poor soul.
I deep-cleaned my grinder yesterday and used my usual medium/light beans tonight and couldn't be happier with the cleanliness of the taste and of the shot.
The dark roast is totally for espresso, not filter, not here anyway. You might find dark roasts in filter/brewed coffee in some other countries but why would you?
The expansion of beans during first crack is due mostly to internal steam pressure being driven out of the bean. there is an overall expansion of the cell structure
with a violent expulsion of pent up steam through small cracks in the bean ends and the centre crease. Second crack is a build up of carbon dioxide pressure which causes the
cellulite in the ever expanding cell wall to disintegrate and physically start to crack. The sounds that first and second crack make are also different, first crack is a popping, popcorn like sound while second crack is more a rustling sound , like coco pops. If you remove the sampler from a roaster during first crack it's not unusual to have beans jump right out of the roaster due to the more violent nature of first crack.
If that's the case, is it possible that these beans were meant for, say, filter rather than espresso? I did try the same beans in that Tokyo coffee shop, they served it filtered and it was good, hence I bought a bag to bring home.
Beans have enough woody fibre/cellulose to hold their shape while the oils and gases burn-off and eventually the fibres turn to ash. You can get them to glow red like little heatbeads but that's not a normal roast depth for most people
Andy thanks to you too. There you go. I learned a lot this morning. I thought (stupidly) that longer roast time equates to smaller beans as the fluid from the beans evaporate! 😄
crazyhakins thank you so much for taking the time and replying!
Re: number two: I think it is very oily. My grinder normally is pretty clean, but with these beans, they clogged the chute! I will do a deep clean tonight now that these beans have finished.
Thanks again.
Last edited by rooroadbikes; 13 November 2022, 11:44 AM.
Reason: Typo
1. Sorta. Some light roasts are not developed enough for the beans to swell, most medium roasts are fully swollen and as you roast darker they get lighter until they turn to ash (or combust)
2: Darker = more brittle but as above, higher volume. Your grinder will take longer because there is more volume to get through.
3: You bought very dark roast! Rubber, BBQ, tar, ashtray... plenty of descriptors that suit what you asked for and you won't find floral, fruity, bright in any
4: that's the brittleness, the beans shatter in the grinder.
5: Yep.
(edit: I need to type faster. +1 for crazyhakins reply that appeared after I hit Post Reply)
Hi rooroadbikes, 1. yes the darker roasted beans are usually bigger because the roasting process causes them to expand due to internal moisture causing a pressure build up - that's what the cracking sound is during 1st and 2nd crack. If a bean has been taken through 2nd crack it will be larger than a bean that hasn't (generally speaking).
2. My experience is that darker beans are easier to grind for exactly the reason you describe, but if they are roasted really dark and are oily on the surface of the bean, that might affect grinding? I'm not into dark roasts so don't have a lot of experience grinding them.
3. It sounds like not a great roast, overdeveloped. That is normal if you scorch the beegeebus out of beans.
4. Sounds like increased static to what you're used to. Do you RDT? That should help.
5. I generally find I need to grind dark(er) roasts finer to get the same extraction time. But my version of a dark roast is nowhere near 2nd crack, and it sounds like your beans might be well on the other side of 2nd crack. If your grinder was struggling to grind them, then you might have got some increased particle distribution, leading to more opportunity for channeling?
Probs a good decision to move on from those beans if you like medium roasts!
A super n00b here, so the following may be a good laugh to the experts, something to mock about on a Sunday morning, so here we go:
I bought a bag of artisan roaster beans from Tokyo. They were very dark roast. About a month later since the roasted date, I opened it, weigh them 20 grams and place them in my capped glass vials. The vials normally fit 20 grams of my usual lighter roast with around 10mm space between the beans and the cap.
To my surprise, 20 grams of these Tokyo beans didn't fit the vials. It can only fit around 12 to 13 grams.
Questions:
1. Are darker beans swell more than lighter ones? I would have thought the opposite as darker roast means dryer, hence should be smaller.
2. My Eureka Mignon Single Dose takes longer to grind 20 grams of these, compared to the usual lighter roast. Why? Again, if my assumption above was correct, then darker roast = dryer = more brittle = easier to grind?
3. After ground, they smell rather unpleasant, almost kin to burned rubber. Is this normal?
4. They were also messier to grind. Heaps of coffee particles shoot off from the grinder's chute. It doesn't normally like that with my usual lighter roast beans.
5. They were also more unforgiving during puck preparation. If I didn't do WDT enough, I got very awful channelling. Very, very messy.
Needless to say, I won't be buying them anymore (not that I go to Japan that often anyway), but I wonder what causes the above?
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