0.1g or 2g?
What a GU63 Retention Test
Really Tells Us
Same grinder. One small change.
A very different result.
The bellows made a big difference.
In a recent Coffeeness review, the GU63 showed a maximum input-to-output difference of 0.1g with bellows. Without using them, the reviewer reported roughly 2g left behind.
dose-weight difference
left behind
Not all retention
is the same.
A near-perfect dose weight doesn't necessarily mean there's no old coffee left inside. These are three different things worth separating.
Input versus output weight for one dose.
Coffee remaining in the grinder after grinding.
Old coffee mixed into the next dose.
Two brewing styles.
Two different experiences.
Espresso
Sweet · Chocolate notesSyrupy body · Long finish
Pour-over
Enjoyable overallSome fines · Less light-roast clarity
With a medium-roast blend, the reviewer found a rich, chocolate-forward espresso.
For V60 and Chemex, cups were enjoyable, although lighter roasts showed more fines and reduced clarity.
Great coffee.
A few trade-offs.
Strong flavor and build quality, but not a perfect workflow.
Measured by Coffeeness under its test conditions.
The reviewer found the attachment less secure than expected.
Some grounds still clung to the dosing cup.
Does low retention count
if you have to use the bellows?
The GU63 achieved a very small dose-weight difference with bellows. Whether that counts as “low retention” depends on how you define it — and how you use your grinder every morning.
