This is a great little (but heavy) grinder. Now retention is an issue, and I will cover this at each step, I trust this is helpful to fellow Mignon owners.

Step 1
Thoroughly clean out retained grinds by removing the top burr, brushing, using a needle to scrape out in crevices, vacuuming from top, and up the exit spout – the vacuum flexible end piece fitted neatly into the spout and was very effective (removing the exit spout after this showed no residual grounds in this area, so for regular cleaning there is no need to remove this for cleaning as far as I can see)

Step 2
Place 35.2 gm of Cafetto Grinder Cleaner pellets into hopper and grind. 26.2 gm of ground up pellets came out. After I brushed the exit spout, and tipped the grinder on its face, with grounds falling into a container, the total out came to 31.1 gm, leaving 4.1 gm inside the machine.

Step 3
Cleaned the machine again as in Step 1

Step 4
Put 70 gm of coffee beans through the grinder. 63.3 gm came out; after tipping the grinder, the total output was 65.5 gm, leaving 4.5gm retained.

Step 5
Cleaned machine again as per Step 1, plus used a hairdryer on full blast (the round end of the hairdryer fitted exactly over the 40mm hole at top) at the top – nothing came out, so any grounds left are resistant to exiting, and would not come out during normal use I suspect.

Step 6
Placed 18 gm of beans into hopper and ground. 12.1 gm came out. Brushed bits of grind at top into grinder and ground again, raising total out to 12.8
gm. After brushing spout while grinder was on its back and tipping forward into a container, the total out was 16.2 gm.

So, with faffing about, the minimum retention is 1.8 gm. This is after only one single dose, putting 70 gm through probably gives a better indicator of retention over a period of a week for example.

Now how was the espresso after all this? Enjoyable cup from La Pavoni Pro. Don’t think I could taste any difference… but I was not drinking pre and post cups side-by-side…