I consider myself fairly well read on espresso, though I lack the cold-hard experience. I have an issue I can't seem to figure out...

My first shot out of the machine for a session (e.g., first shot of the morning) comes out perfect (35s @ 2oz approx.), tastes good. Then I go to make a second shot, using the same ground coffee from the doser (no stale grounds initially, doser cleaned out daily), and it simply gushes to a blond spew within 10 seconds. Same grind, same dose, same distribution, same tamp, dry basket before each... I cannot figure it out.

I was thinking it was some sort of severe channeling issue, as I sometimes get a quick side squirt as the gush commences. I'll sink this shot, and then (as the case last night) pull two more shots, with the same gush results (1 good first shot, 3 gushers in a row). The only way I can seem to stem the gushing is to grind a bit finer, but then this results in a severe change to say 45 secs. @ 1.5oz (which makes sense in relation to the first good shot). Perhaps due to this particular coffee? I didn't have this issue with Black Cat. Is there something else I'm missing?

Why are these second and third shots behaving so erratically? This doesn't always happen, only during some sessions in last week.

Machine: La Spaz S1 VII
Grinder: Cimbali Jr. (@ approx. 3.5)
Coffee: Paradise Espresso Classico (fresh within a few days out of freezer; frozen 2 days after roast, tight in mason jars)
Dose: 15gr. using a 0.1gr scale (leaves a moderately soupy puck, sometimes tighter than others)
Tamp: 20# consistent using scale
Brew pressure: 9 bar
Method: I dose into a ramkin, weigh precisely, spoon coffee into dry PF, distribute with a dissection needle (a la WDT, sans yogurt cup funnel), tamp, pull.

I also have filters and pressure regulator on the incoming water line for the machine. So inconsistent pressure shouldn't be an issue.

jmvdigital wrote:Then I go to make a second shot, using the same ground coffee from the doser (no stale grounds initially, doser cleaned out daily), and it simply gushes to a blond spew within 10 seconds.

Um, just checking. Do you mean you grind once and fill the doser in the morning, then come back later to make shots from that coffee?

jmvdigital wrote:Paradise Espresso Classico (fresh within a few days out of freezer; frozen 2 days after roast, tight in mason jars)

How long has that coffee been kept in the freezer and how cold is your freezer?

As you are learning there are an awful lot of variables.

- Are you filling the hopper or just putting in enough beans for current use? The popcorn effect caused by a nearly-empty hopper can cause grind problems. If you suspect grind, then grind for current use, remove it all from doser, and mix the coffee, then dose from there. See if that makes a difference.

- A 20 pound tamp is fairly light and requires a very fine grind. Try a 14 gram dose (leaves more headspace), and a heavy tamp, and then adjust grind to match. This might help eliminate any other problems...

Here's an off-the-wall guess- after the first grind the grinder develops some heat and static increases- this causes more clumping in the coffee as it sits in the doser and the channeling problems and fast flow...

Have you been wearing your official issue Home-Barista.com aluminum foil cone hat when tamping?

Another_jim: I usually grind enough beans for 3-4 shots at once, and let it sit in the doser in the morning while I make various drinks and shots. After I'm done making espressos for the morning I'll clear out the doser and grinder completely (brush it all out) and scrub the screen and backflush the machine a few times and shut it off. Sometimes I make espresso at night, sometimes not, so I usually just clean up with the assumption that I won't.

Stuggi: The Paradise coffee was roasted Sept. 17th, and in my freezer since the 19th. I split up a 5lbs. bag into smaller mason jar and froze them. I don't know the exact temp of the freezer right now, but it was around 0-deg. It's bottom door freezer on your standard fridge. It gets opened and closed randomly in our household (I know, not the ideal for a deep freeze ) .

Randy: Good lord there is a lot of variables. My fiance thinks I'm insane. I don't fill the hopper, I usually just pour in enough beans for 3-4 shots worth. I never thought about it, but I can see how the popcorn effect might impact the grind. In this particular instance though, I was using grounds from mid-grind (i.e., not from the tail end w/ popcorning).

A 20# tamp is pretty light. But considering I have been able to get (what I think, anyway) decent pulls, would there be a reason I would need to adjust the tamp if I have the grind set sufficiently tight? My understanding was that the tamp really didn't much matter as long as you were consistent? For what it's worth, I'm using a convex Bumper tamper from Chris'.

I definitely notice clumping in the doser from the grinder. I haven't attributed any clump characteristics to grind time, but I can pay attention next time. I have noticed, fwiw, that if the chute is clear on the Cimbali Jr., the grounds come flying into the doser and hit the doser wall closest to you; after a second or two of grinding however, the chute cakes up and grounds just start falling clumsily into the doser. I was hoping that my stirring with the needle (WDT style) would render these clumps impotent. Perhaps not?

I appreciate all of your feedback so far. Keep it coming. Thanks again.

-Justin

Ground coffee stales in minutes, and its flow will increase at that point. Grind fresh for each shot.

Jim, we're talking about coffee that has been ground within minutes of being used. You really think that is the culprit?

jmvdigital wrote:Jim, we're talking about coffee that has been ground within minutes of being used. You really think that is the culprit?

I thought you meant you grind the coffee, and use it over the course of the morning, i.e. several hours. If you are making several shots at once, disregard what I said.

Randy probably has it here: Popcorning is the likeliest culprit, since the grind needs to be finer when the beans are not loaded down.

another_jim wrote:I thought you meant you grind the coffee, and use it over the course of the morning, i.e. several hours. If you are making several shots at once, disregard what I said.

Randy probably has it here: Popcorning is the likeliest culprit, since the grind needs to be finer when the beans are not loaded down.

If the shots are back to back, sure, grind a little extra.. if not immediate, grind per drink.

The Cimbali grinder hopper is not well designed for running empty (and maybe none are meant to grind empty, see the corresponding poll, Do you dose and then run the grinder until empty for each espresso?). I like to keep it about ~0.25 lb in the Cimbali hopper all the time whenever I can.

As an interesting side note, the Mazzer Super Jolly grinder also seems to change as it approaches empty. I've been using a small paper cup as a hopper and a tamper for weight on the beans. I've not taken time to correlate the effect of the hopper going empty on shot time, but, contrary to what I would've guessed, once the tamper weight is off the beans, it actually grinds a bit FASTER. I've noticed this several times now, since I count to 8 or 9 for about 15-16g. A couple times when the grinder was near empty, I had lots extra in the doser (a scale confirmed I still had the dose I was looking for in the basket).

Randy G wrote:Have you been wearing your official issue Home-Barista.com aluminum foil cone hat when tamping?

Some days, I need one of those too...

IMHO, what you probably got with your first shot was your God shot. Yes, grinds stale quickly so maybe your subsequent shots suffered from some staling but I think you got the dose, distribution, tamp really on for your first shot and you were off on your next shots.

Going finer with the grind got you a ristretto. Makes sense if the grind before was fast because of channeling.

Practice makes for better control. The control is in the hand if your roast is fresh and your grind is good. Yeah, popcorning could be an issue but if you put weight on your beans to prevent popcorning and still get channeling I'd say it's your hand.

How did the subsequent fast shots compare in taste to your first shot?