another_jim wrote:I don't think this is right. It is not a repeatable measure, for instance, a humidity change will alter the fluff of the grind and the weight you will use. Moreover, a finger strike dose has no bearing on any aspect of the shot.
Jim, thanks for weighing in. Humidity is one reason (other than convenience) to prefer dosing by volume over weight. But I disagree about finger strike dosing. Leveling to the top of the basket (or any specified distance down from the rim) certainly has a bearing on headspace. It provides a fixed, consistent reference point for dosing a basket.
another_jim wrote:I don't think there is a unique natural fill level for a basket. However, in general, I think one can nominate a certain dwell time, e.g. five seconds from pump on to first drop, as optimal for ones machine (or at least the optimal starting point for a new coffee). Since head space determines the dwell time, a fixed dwell time will establish a unique dosing level for each basket, and also the equivalent dose levels across baskets.
Excellent suggestion. It should not be terribly difficult to measure dwell times* for different doses... um, not sure where to go from there. Compare the taste profile of similar dwell times across different baskets, maybe even machines? You'd be much better at that than me.
another_jim wrote:Why use dwell time for picking the natural dosing level of a basket? Longer dwell times reduces the chance of channeling, but arguably adds some over-extraction muddiness to the flavor earlier in the shot. So dwell time is a variable for shot quality. Since the fill level of a basket determines the dwell time, and one can always change baskets to change dose, using dwell time to define the fill level seems to be the "natural" way to go.
Certainly would be interesting to see the correlation between grind, dose, dwell time, and taste. Grind and dose both impact dwell time. I assume you'd want to adjust the grind for the overall extraction, not the dwell time.
* "The dwell time, the time it takes from turning on the pump to seeing the first drops of espresso emerge from the basket varies from machine to machine." The Home Barista's Guide to Espresso