I changed the coffee from Jamaican Blue Mountain to some freshly roasted Mocha Harara and put it in the Macap M4D at the same setting I have for the Blue Mountain. It hardly came out.

As I moved the setting to coarser and coarser the flow slowed more and more ??? This was contrary to what should happen..

Finally I moved the setting from 7.5 to 8.1 (a big move) and things started flowing better.

Then I pulled 2 shots in a row and the first one was correct and the second one hardly flowed again ?? This is a puzzlement. I used the same amount of coffee, same pressure (acaso 30lb tamper) so I'm trying to figure out what I did. Any ideas.

I did measure the amounts by "eye" rather than using the digital doser measuring seconds exactly so that could play. Its definitely weird

No its not weird at all. Its different coffee. Different coffees will require different grind sizes (some seemingly drastically different) beyond the typical adjustments for bean age.

IMBO, when making a significant grind / coffee change, it takes ~3 shots for things to settle to the point that picking the pepper can begin.

Welcome to the elusive and never-ending quest to understand espresso - and to the impossible goal of achieving anything close to repeatability in your shots.

misterdoggy wrote:As I moved the setting to coarser and coarser the flow slowed more and more ??? This was contrary to what should happen..

Something that's often overlooked is the expansion/swelling of the coffee. If, for a particular roast/blend, you have a grind that is so fine that it impedes water flow, you make the grind coarser. But then what can happen is that water flow is improved, and as more water drenches the coffee bed, it swells, which again can impede the flow. The flow may be just as tight as, or tighter than, a finely ground bed which did not get fully saturated. So you make the grind even coarser, and then finally you have both a freer flow and a swelling of the coffee bed from the infusion.... optimal.

Something that's often overlooked is the expansion/swelling of the coffee. If, for a particular roast/blend, you have a grind that is so fine that it impedes water flow, you make the grind coarser. But then what can happen is that water flow is improved, and as more water drenches the coffee bed, it swells, which again can impede the flow. The flow may be just as tight as, or tighter than, a finely ground bed which did not get fully saturated. So you make the grind even coarser, and then finally you have both a freer flow and a swelling of the coffee bed from the infusion.... optimal.

This make sense to me. I would like to find the blend that I really like above all others and stick with one blend one formula to make the great shots and stay in that world of the "sure thing" for while.

Still trying different belnds always 100% Arabica ie: Italian (too bitter), Indian (not bad at all), Jamaican (liked this one too, Now am trying out Mocha which has been the most difficult to regulate tamp.

I'm looking for something sweet and chocolate tasting not bitter but fruity for use only with latte's

timo888 wrote:Something that's often overlooked is the expansion/swelling of the coffee.

The coffee bed expands AFTER extraction has ended (when the 3-way is released).

malachi wrote:The coffee bed expands AFTER extraction has ended (when the 3-way is released).

The coffee swells as it absorbs water. Substantial swelling can occur as early as the preinfusion phase. Depends on the nature/extent of the preinfusion.

http://www.home-barista.com/espre...-t2047.html#p18757

Particles swell, the bed compacts.

I think we oughta get a spy cam in there to settle this

personally I would think that the moment water touches anything it starts to absorb which causes expansion to a degree