I'm working on a three-year old Expobar Lever. There has been a recent change in my espresso extraction; I just returned from a two-month overseas trip and the machine was off all that time.

I dose and tamp as per my usual. The extraction starts out fine (I hit the brew switch and start my timer) and after about 4-5 seconds the flow begins. It seems thin and restricted compared to before and I know that in 25 seconds there will not be a complete double shot. I'm only at about one shot when extraction is 4 seconds or so to go.

At that point, there is a change in the sound of the machine (the pump?), and the flow increases dramatically, almost splashing now into the cup. I can still stop at 25 or so seconds and the crema actually looks pretty good. I would say the taste is just okay.

Does this sound like a tamping challenge? I did a backflush and clean, just in case, but that didn't seem to affect it.

I wondered also about my pump; it was replaced by me about a year ago.

Advice is welcome.

Thanks,
Craig

CTurner wrote:At that point, there is a change in the sound of the machine (the pump?), and the flow increases dramatically, almost splashing now into the cup.

Sounds like channeling. Is the coffee fresh? Stale coffee ground extra fine will start dark and slow, and then suddenly "let go" mid-shot as you describe. Could you post a video?

I recently had this happen and my machine (and hopefully my skills) were previously quite consistent, so it may not be the machine.

I agree about the beans and I just picked up a new batch so I'll be trying this out tonight. I suggest getting other beans and trying again.

Canuck wrote:I recently had this happen and my machine (and hopefully my skills) were previously quite consistent, so it may not be the machine.

I agree about the beans and I just picked up a new batch so I'll be trying this out tonight. I suggest getting other beans and trying again.

Tried a new blend tonight and thankfully, it was the beans. This blend poured very nicely and tasted great.

There is almost always a dent or beginning of a depression at the handle edge of the puck after extraction. Different tamping and grinding methods don't seem to affect it at all. There are no holes in the bottom of the puck; could the water be somehow working its way on the edge of the puck suddenly? Can anyone suggest a different method of tamping?

I did a series of about 10 shots this morning and every time, at about 10 seconds (timed from first appearance) the sound changes and the overflow starts.

I'm pretty sure the beans are fresh from my local roaster, but I suppose another pound or two wouldn't hurt to experiment.

Craig

Uh, one more element...

I have never replaced the burrs on my Rocky...three years old, could this be an additional cause?

Thanks,
Craig

CTurner wrote:There is almost always a dent or beginning of a depression at the handle edge of the puck after extraction. Different tamping and grinding methods don't seem to affect it at all. There are no holes in the bottom of the puck; could the water be somehow working its way on the edge of the puck suddenly? Can anyone suggest a different method of tamping?

Unless your tamp is badly canted, the more likely cause is a distribution problem. From the troubleshooting checklist:

Channeling from the edge?

This could be caused by too much tapping or rapping the side of the portafilter after the first tamp; consider a Staub tamping style. Another possibility is the top of the puck is grinding against the dispersion screen during the portafilter lock-in; verify there is adequate clearance to allow the puck to expand up to meet the dispersion screen. If channeling is near the handle, remember to rotate the portafilter while dosing to avoid front-loading the grounds and confirm you are not "working around" the handle when distributing.

CTurner wrote:I have never replaced the burrs on my Rocky...three years old, could this be an additional cause?

A new set of burrs aren't expensive and they are likely overdue for replacement. Rocky burrs are good for ~75 pounds of coffee.

If you want to experiment with distribution and tamping you may want to read, and watch the video's in the Tamp and Dose Techniques Digest.