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

Sure you just didn't have some grounds from the prior grind in the doser circle back around for dosing after the good shot? (Or break loose if using an electronic doser - I haven't seen an MD4 so I don't know what kind of doser we're talking about here.)

I often find that if I'm changing grind shot to shot, especially big changes, I really have to empty it out carefully between shots or I'll end up with in-between shots with some of the current grind and some of the previous grind in the basket.

M4d Macap doesn't have a Doser basket, rather a direct chute so there is hardly any previous grains and the main reason I decided on this model. In fact I don't understand why anyone would buy a doser. Such a pain and always old grains to clean out. This one you run it for 2 or 3 seconds and you have run out the old grinds and ready for the new setting.

I think it has to do more with the freshness of the Roasting as the beans were roasted the day before. It takes about 8-9 seconds before anything comes thru and then woosh it comes very fast. Its packed with the same pressure and same amount each time. Tastes good though So I won't complain. Just not that "honey" pour at that perfect rate I've been looking for.

Well, if the chute has a sweep mechanism and really doesn't hold any grounds (i.e., nothing stuck in there that could have fallen off), sounds like it might be a distribution/dosing problem? If you weren't weighing the beans or timing the grind, perhaps you just got a big enough dose variation to substantially change the flow. (E.g., if the "good" pour was from a fluffy dose with no clumps, and the second from a clumpy dose with substantial higher density areas.)

Well, it has a digital timer so the amount or time is always the same. Something to do with the second pull after the first. The first flows faster than the second. I wait enough time for pressure to come back, not that there isn't sufficient pressure for 2 pulls. The first one flows better than the second which slows down.

I wipe out the basket. tamp exactly the same. 30lbs then 3 turns to solidify after gently tapping to remove edge grinds to the center. The pulls with freshly roasted Mocha are very temperamental.

HB wrote:Less clumping.

Sometimes

misterdoggy wrote:Well, it has a digital timer so the amount or time is always the same. Something to do with the second pull after the first. The first flows faster than the second. I wait enough time for pressure to come back, not that there isn't sufficient pressure for 2 pulls. The first one flows better than the second which slows down.

I wipe out the basket. tamp exactly the same. 30lbs then 3 turns to solidify after gently tapping to remove edge grinds to the center. The pulls with freshly roasted Mocha are very temperamental.

How long has the grinder sat before the first shot? Ground coffee stales very quickly. If you purge the grinder for a second before the first shot, does the shot to shot consistency improve?

malachi wrote:Particles swell, the bed compacts.

OK, fair enough.

The ground coffee takes on water, swells, requiring increased pressure to push water through the swollen coffee. But if the requisite pressure exceeds ~9 bar, flow can diminish or even stall ... probably because the bed compacts under the pressure which results in an even more densely compacted medium. So for a proper extraction you want to find the dose, grind, tamp, and pressure that combine to produce an optimal flow, and as you know from much experience, these factors can vary by roast-depth, roast-freshness, and bean-blend, among other factors (I haven't even mentioned temperature).

misterdoggy wrote:Well, it has a digital timer so the amount or time is always the same. Something to do with the second pull after the first. The first flows faster than the second. I wait enough time for pressure to come back, not that there isn't sufficient pressure for 2 pulls. The first one flows better than the second which slows down.

I wipe out the basket. tamp exactly the same. 30lbs then 3 turns to solidify after gently tapping to remove edge grinds to the center. The pulls with freshly roasted Mocha are very temperamental.

I thought you said you had not used the timer for dosing here? In any event, are you using WDT or another method for distribution consistency?

misterdoggy wrote: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

Between Illy, Nestle, La Spaziale and the myriad enthusiast researchers believe me the research has been done.

Guys guys guys...

You're over-complicating.
This is simple.

misterdoggy wrote: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.

Different coffees (and in fact the same coffee on different days or at different points within a single day) require different grind settings. Fact of life.

misterdoggy wrote: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.

Flow rate is not purely dependent upon grind setting.

misterdoggy wrote: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.

Here is the clue that explains the above. Consistency and repeatability (in flow much less in taste) are NOT simply the result of tamp pressure and grind.

misterdoggy wrote:I did measure the amounts by "eye".

Given that you are relatively unpracticed when it comes to dose it is very unlikely you're consistent with your dose to less than 0.3g (much less the goal of 0.1g).

Dose consistency is far more important that tamp pressure consistency (for example) when it comes to consistent results.

Beyond this - it's likely that your distribution is also inconsistent.

As the old HB saying goes... "the problem is on the handle side of the portafilter".