I'm reaching my wits' end trying to figure out what's going wrong here. My shots are consistently gassy no matter what I do -- except for when I pull them within a minute or two of the thermostat light's first clicking off, i.e. when the boiler has gotten up to temp but before the rest of the machine has absorbed all that heat.

Ordinarily I would think that it's best to wait a few extra minutes specifically for the purpose of heating the machine all the way through, for best temp consistency. But when my machine is heated through, the shots are gassy!

I've isolated and adjusted pretty much every other variable I can think of.
Grind: finer, mid-range, coarser
Tamp: lighter, avg, harder
Dose: a bit less, a bit more, usually around 20-21g
Distribution method: WDT, stocksfleth, settling, no settling, etc
Extraction time: Usually around 25-30sec but I've experimented with anywhere from 20-60sec
Roast: city thru FC+
Days off roast: 4-10 and beyond, including store-bought mystery-age
Origin: Yirg, Sumatra, Guatemala, blends, etc, pro & home roasts
Cooling flush: longer, shorter, none
Boiler pressure/water temp: I've tweaked it higher & lower but tend to leave it at a heat cycle peak of about 1.1

No matter what I adjust, my shots have consistently finished with a thickening stream and big gassy bubbles, making for an overblown crema that dissipates down to nearly half the volume the shot originally appeared to be. The pucks are flat & evenly solid, neither soupy nor pitted; no significant issue with channeling jets during extraction; no burn marks on the bottom of the basket. Extractions tend to unify into a single centered stream around 10-12sec, but after the 20sec mark comes the thickening of that stream and big bubbly ooze. The shots do still taste alright by my standards. Rarely amazing, but still better than anything I could be served locally, so I keep at it. But I know my equipment should be able to achieve better, and on this same equipment a year ago I didn't have this problem.

I'm working with a '91 Livietta (old ULKA pump) with bottomless PF (triple basket, I believe), a Baratza Vario and a Behmor. No mods to anything. Roasting with the Behmor I know that peak flavor-balance & espress-ability tends to occur after about 10 days' rest, even though I never actually wait that long.

I pull 2 or 3 shots a day, and I admit I will sometimes go longer than I should between backflushings, however this week I flushed twice and the issue persists. I also notice that when the machine is fully heated, the group solenoid seems to be a little less efficient. At a cold start, turning on/off the pump = water starts & stops, no drips at all, but when fully heated, a few drips will still come after hitting the water switch off. I don't know if this would have anything to do with it; just an observation.

The only thing I can do in order to pull a decently fizz-free shot is to pull that shot before the machine heats through, but this shouldn't have to be the case, and I'm sure I'm not getting the best from my coffee this way. Any advice or ideas from the HB denizens is welcome & appreciated!

Just checking. You are using COFFEE beans, right?

Wait a minute... you mean this isnt the fava forum?

I've never heard anyone blame gas on espresso before, I'll have to try that on the wife tonight!! Sounds to me like you need to re adjust your grind.

sonnyhad wrote:SNIP<<<< Sounds to me like you need to re adjust your grind.

I think OC covered that with his comments on grinds, doses, tamps and shot times.

I know I've been having the very same issues as he does with my Classic paired with a LeLit and beans roasted in a Behmor.

I've tried everything he's done, with the same level of success (still gassy shots) .........................................

""EXCEPT""........... I've never paid attention to how long the machine had been on. Due to when I drink coffee, the machine is always on for 1/2 hr or more before I pull a shot, and it's always after a cooling shot.

This evening when I get home I'm going to try a couple 10 or 15 mins after I turn it on, and will post back results here.

Jamie

These symptoms, for me anyway, have to do with the coffee. Dark roasts with robusta do this for me. More rest helps, ten days to two weeks post roast. I get thee symptoms with a select few blends from Italy and from a local "Italian style" roaster.

Try different coffees (lighter roasts, 100% arabica)

Good luck

Bit left field, but have you been using the same basket as you were before the problem started? I have two double baskets that have almost identical dose but one is a shallower wider one (LM) with larger holes and one is a deeper narrower one with smaller holes (Faema style). The LM allows me to fine up the grind, producing great tiger striping in the first 15s but the subsequent flow rate increases faster than the other basket, often forcing me to cut the shot at a lower total volume than the Faema basket with coarser ground coffee

Just a thought

Thanks for all replies!

Jamie: I look forward to reading your results

Mario: An astute recommendation, but I actually never brew robusta. Been meaning to try it, actually; but my home roast is always Arabica.

Ben: By Jove, I think you're onto something! When I switched to the bottomless PF, I also switched baskets. (see this thread for details and a photo of the 2 baskets, side by side but unfortunately no examination of differences in hole design: Bottomless Portafilter for Vintage Pasquini Livietta) I can't say for sure that this was exactly when I started experiencing the bubbly shot syndrome, but this is actually the one element I overlooked in all my other adjustments! The basket! Due to poo roast scheduling I will be Aeropressing a local roaster's Peru for a few more days to allow my latest roast its adequate rest, but ASAP I will pop my old basket in there, see how it goes and report back after a few shots.

Here's a couple images just to illustrate the bubbly shots I'm talking about. At its worst the bubbly situation is worse than the below, but below is sadly all too typical of shots lately. If I recall, this shot is a Guatemala Huehuetenango SO, Behmor'ed to about FC. It's the 2nd shot of the day, machine's been idling for a while, 21g dose, 25sec extraction, not sure of precise volume. I let it go til the surface of liquid was just about as high as the demi would hold, as you can see from the point where the residue stops in the photo at bottom. That's the same shot a minute or two later, after the overblown crema has dissipated. It dissipated even a bit more after the photo.

Hope it helps, ill be interested to hear.
The bottomless PF by nature will make larger bubbles since they dont get broken up by the spouts but thats some voluminous crema you got there! You can also try shifting the cup over a bit so the stream runs down the side instead of straight to the bottom, should help a little

I've seen this occasionally on my Ellimatic HX, and, aside from the time it was caused by my not having sufficiently tightened the screen bolt after a thorough cleaning, I've always been able to fix it by tightening up the grind, sometimes a bit more than I expected to have to. Since my machine is on solidly from Friday evening to Sunday evening every week, it's temp stable from about a half-hour after i get home from work on Friday until I turn it off late Sunday.