Mythos was positioned as one of the lowest retention hopper-fed grinder due to its inclined burrs design. So it happens that one of these came into my possession and I decided to put it to test. What I am measuring is the total retention in the system, disregarding whether it is static or dynamic retention. Dynamic retention (the practical retention) will likely be lower because there'll be some compacted 'ground' that never get mixed into freshly ground coffee.

First, the obvious - chute:



~3.2g in the chute. As you can see in the pic above, the older chute retains quite a bit there. It should be reduced greatly with the new clump crusher.

This was how it looks immediately affter disassembling the upper burr mount. Do note that I can't remove 100% of the beans above the burrs prior to disassembly. So all these were removed and sieved for measurement. The chute's retention was collected first, separately):


Separating the whole beans that I didn't manage to remove prior to disassembly:


Partially ground+fully ground


Separated the bigger chunks using a fork:


~1g of chunks, and ~8.3g of fully ground coffee. Edit: I sieved the 'fully ground' portion with a finer mesh and there are about 2.3g extra chunks(partially ground coffee). So it should be ~3.3g chunk and 6.0g fully ground coffee.

In total, there is a total of about 12-13g coffee retained in the (older) system. With the new clump crusher, I would expect that to be about 9-10g. It's not totally zero retention, but pretty good for a hopper feed system.

Looks like around 60 whole beans...should be around 6 grams no? So where were the 60 beans located that they couldn't get crushed?

Where did you get the 60 whole beans number?

I did not measure the sieved whole beans because those are the beans I didn't manage to remove prior to diassembly. I just want to know how much ground/partially ground beans are in the system. Whole beans are not included.

add on: Oh, if you did this exercise before you will realize you can't remove 100% of the whole beans from the neck/throat. Those whole beans you see are exactly that. They're sitting above the burrs (before being fed into the burrs), together with the partially ground beans.

Nice work!
The "one gram" retention rumour mill has already started, though... so it'll be a tough battle against it!

This is the graphic (5 min MS paint job) representation of what I'd found: