Should be heavily compressed, and there is nothing in the bean structure to support such pressure.
A roasted bean is very porous, just drop water on the surface and see how is absorbed.
Also, most degassing happens next day after roast, about 80%, the rest of 20% happens in the next 3-5 days.
Surely not during grinding.
It's simple to demonstrate that ZERO retention grinding can be obtained with any conical grinder, if well brushing before and after, you will get not even 0.1g loss, so gas weight lost due to grinding is a myth.
Flat burrs are other story though... lots of places to get grounds trapped... and draw wrong conclusions.

The CO2 and CO gas that is trapped in the beans after roasting is actually mostly trapped within the cell walls, not in the porous area between them.
But I find the debate on the weight of this gas and it's effect on retention numbers mostly philosophical, since the weight is really negligible (especially since if you want to weigh something in earth's atmosphere, it has to be denser than air - and that would mean very compressed CO2: air density is 1.29g/L, CO2 density is 1.87g/L, after taking CO2 buoyancy into account you are left with only 0.58g/L that you can weigh)
This is similar to the guy that tried to weigh the human soul by weighing people before and just after they died and came up with an arbitrary number 21g after a lot of bad math, physics and biology.

Right, what we have as tangible evidence is the weight loss during degassing: 2-3 grams @ one kg of roasts after first day, about one more gram next days, exact values depending on roast degree.
This means about 0.3%, and similar ballpark values can be found in scientific papers about coffee roasting.
These 3 grams of CO2 means about 1.5 litres volume, that exhausts through the bag valve during degassing.
This is observable even at home, if the beans are sealed into a large enough (transparent) bag, and vacuumed right after roasting.
If this bag is placed into a glass recipient like French press, the gas volume will be very visible, as the sealed bag inflates and rises.

Daedalus wrote:Question for the folks reporting low retention: I am having tremendous difficulty with retention consistency on mine. I've tried a range of spray or droplets mixed into the beans, and sometimes it works perfectly for a while, then it will retain a full g or more.

Are you using water, RDT, any of that? I can't figure out if I'm doing too much, too little, or luck of the draw.

Yes, I stir beans with the handle of a teaspoon dipped in water with excess shaken off.
Retention without doing this can be as much as 0.5g for me, but after doing this I consistently see 0-0.1g retention only.
Also, helps to remove grinder body from motor once stopped and with the grind catcher in place, and tap on the countertop/teatowel to displace any remaining grinds also - just my workflow.

renatoa wrote:Right, what we have as tangible evidence is the weight loss during degassing: 2-3 grams @ one kg of roasts after first day, about one more gram next days, exact values depending on roast degree.
This means about 0.3%, and similar ballpark values can be found in scientific papers about coffee roasting.
These 3 grams of CO2 means about 1.5 litres volume, that exhausts through the bag valve during degassing.
This is observable even at home, if the beans are sealed into a large enough (transparent) bag, and vacuumed right after roasting.
If this bag is placed into a glass recipient like French press, the gas volume will be very visible, as the sealed bag inflates and rises.

Yes, exactly, there is gas in the coffee, but when you apply these numbers to my morning 12g brew grind of coffee that was roasted 3 weeks ago, you get something that your 250€ Acaia with it's 0.01g (by the way, have ya'll noticed they actually wrote 0.01g readability, not accuracy or repeatability on the bottom - mostly, because the accuracy or repeatability is nowhere near that - and it doesn't need to be for making coffee) can't even dream on picking up on.
So we should really stop this nonsense of talking gas content and how it relates to grind retention number results.

Ok, so I guess i misinterpreted Smrke's slide - the 1.0±0.2% figure is only accurate for the beans they used - probably a dark roast. Still, there's upwards 0.2-2.0% gas in freshly roasted beans according to his paper and sources: https://pubs.acs.org/doi/pdf/10.1021/acs.jafc.7b03310

Even dark roasts were still degassing after 16 days. The rates were high enough that weight loss would still be measurable after 2 weeks. The grind setting probably has an impact, sure.

Has any indiegogo backers receive theirs yet by chance?

I doubt... there should be an unique pool for both KS and IGG at Goat warehouses, and this is empty atm, still 700 KS positions to be serviced.

Speaking of the devil I just received my DHL notification this morning. A pleasant surprise yay. I'm #218 on IGG fyi.

Edit: delivered 11/15/22!

Excuse the laziness but this thread is 40+ pages now. What is the consensus setting for espresso (med dark roast)? I saw some yt vids where they suggested going 15 clicks finer than the suggested 0/30-60 on the catch cup. TIA