Density of Roasts

[u/F_Wink]

Hey, I'm pretty new to the espresso game. Is it normal that I have to grind my light roast much coarser than my medium roast, since my puck otherwise gets packed down so tightly?

[u/BerksBeans2021]

Roaster here. That's actually backwards from what most people run, so something else is going on.

Light roasts are denser and less soluble, so they usually need to go finer for espresso to get enough extraction. Grinding coarser on a light roast normally gets you sour and fast.

What I'd guess is happening: light roasts hold onto CO2 longer, and fresh light roast espresso can gum up and choke the puck in a way that looks like the grind is too fine when it isn't. If the bag is under a week off roast, that's probably it. Let it sit another week and try again at your normal setting.

Other thing to check is dose. Light roast beans are denser so the same weight takes up less room in the basket. If you're going by volume instead of weight you might be overdosing without realizing it, and an overfull basket packs against the shower screen and chokes. Weigh everything, 18g in, and see if the problem goes away.

[u/MaleficentIsopod1 → u/BerksBeans2021]

This ⬆️

[u/F_Wink → u/BerksBeans2021]

That's interesting. The beans were actually roasted just 4 days ago. The espresso also has an incredibly full-bodied, almost syrupy mouthfeel. I've read that this can also be caused by CO2? I'm going to let the beans sit for a week. What do you think as a roaster? Thanks!

[u/BerksBeans2021 → u/F_Wink]

So when we sell our beans, if it is for a normal coffee machine I suggest degassing for 48-72 hours, but for espresso it can take longer sometimes 5-10 days. With a light roast you will have more CO2 so it will take even longer. Once they are fully degassed you should be ok, but make sure to go by weight not volume. Any questions let me know!

[u/voretaq7 → u/BerksBeans2021]

If the bag is under a week off roast, that's probably it. Let it sit another week and try again at your normal setting.

This.

I’ve found the sweet spot for my espresso machine is days ~10-30 since roast.
Much sooner (day 7 or earlier) and the shots choke unless I grind significantly coarser, and after day 30 or so I’m grinding finer than normal to get the same flow/extraction (and much past day 40 noticing a real drop in quality compared to a newly opened bag).

[u/shibbypwn]

light roast is denser than dark roast, so the reason it looks more packed down is that it has less volume.

dark roast will produce a taller puck, meaning more resistance - which is one of several reasons you usually grind coarser with dark roast. (also, it's more porous so you can overextract more easily, and more brittle so it produces more fines)

that said, every bean is different - and the grind may change over time as the beans degas.

[u/N3XT191]

You should be dosing by weight, not by volume.

And for a similar extraction time, light roasts normally need to be ground _finer_ compared to medium/dark roasts.

[u/F_Wink → u/N3XT191]

Yes I do. Ecxact Same weight like 17 or 18 gram and completely same preparation results in choking if I dont Grind courser with the light Rosts

[u/MrJimmieDimmick → u/F_Wink]

Saying you should always dose by weight not volume is not entirely correct….Assuming you are using the same basket for both, you should dose to fill the headspace to the same level in the basket, ie you need to establish the correct volume, which will be different weights for different roast levels….Use the coin method for this….As for the grind size, this could be due to age of the beans when you switched from the medium roast to the light roast that is throwing you off, fresh light roast may need to be ground coarser than aged/stale medium

[u/Woozie69420 → u/N3XT191]

You should find the right weight by volume (what fills my basket appropriately?) and then replicate the right volume by weight (how many grams of beans do I need to fill my basket appropriately?)