Since replacing the burrs in the MC4, I've been experimenting with varying effective bean columns above the burrs. On both the MC4 and MXK, using a timer, the doses are more consistent AND, more importantly, the taste is more balanced when the bean effective bean column height is about the mid point of the standard hopper. As the bean column shrinks, the dose becomes more erratic and shot consistency suffers. Bitter flavors are too prevalent, blonding can be hairtrigger and shots tend toward the thin. Adjusting the dose to ±0.1g does not mitigate the defects.Sherman wrote:Popcorning can be mitigated by placing a tamper, backflush insert, or other similarly fitting device in the throat, on top of the beans.
With a heavy weight like a tamper, shots tend toward the muddy and flat.
Typical 57mm tampers range from around 300 to 500 grams. Coffee weighs about 20g per inch in a 57mm diameter, so the effective bean column height is 15 to 25 inches, much higher, and heavier, than beans in a hopper.
For the MC4, a small water bottle with about 75g works well. For the MXK, with its conical burrs, about 150g.
Note : I always purge the grinder for a second before grinding the dose. These are impressions only on e61s pulling medium roast, moderate ristretto, low dose, mid temp singles, and as always YMMV.