I decided I was dosing too much, so I lowered the dose. Despite discussing it before, I think I'm finally internalizing that my machine has very little headspace and I need to super-down-dose. So I dosed 18 grams into a 22gVST. The shot came out great, and the puck did not expand up into the screen. I repeated this 2 more times and received great shots both times. I solved all my espresso woes!

Went on a 2 week vacation.

I tried to do the same exact thing, but now the puck is super-expanding way up into the screen, hard and I'm getting channeling and gross shots. The beans are from the same batch (frozen in separate mason jars) and I am using freshly defrosted beans (pulled the jar out yesterday, defrosted completely before opening the jar) The age of the beans is the only thing I can think of that is different than 2 weeks ago, but I can't imagine 2 weeks in the freezer would cause the puck to behave like this.

I redid the nickel test and the dose is definitely small enough that it shouldn't expand and push up hard against the screen like it is. Any ideas on what could cause super-puck-expansion?

I suppose there was no chance you lost power while you were gone and you had a major defrost? Because a defrost and refreeze would not do nice things for your coffee.

Ambient humidity changes, grind changes, temperature change?

a couple of bags of stumptown today. 7 days old.
I tried multiple baskets (ridged, ridgeless, VST, HQ), different grinders, different doses, it's all super-expanding. About 15 seconds into the shot, the cone turns into a tornado and everything just collapses from there. I bet thats when the puck hits the screen.

It is drier now than it was 2 weeks ago. Not sure what to do about that.

I'm going to try super-low doses tomorrow. start at 14g in a 22g basket and work up from there. See how that works tomorrow.

I went through more than a bag of beans today and not one decent shot. I'm about 3 days from selling everything and kicking this espresso thing to the curb!. arggh!

thinking simply...expanding coffee usually has to do with the degassing of the coffee...so...maybe it's just the coffee(the stumptown too)?

btw wondering if youre doing any sort of preinfusion and what kind of tamp you're doing. i know the pressure of the tamp isnt important but wondering how high the grounds are after your tamp.

i wonder if using a larger basket is actually making it worse. considering that it would require more volume of water to fill up the basket before full pressure is achieved, maybe all that water is just creating more outgassing?

these are just guesses in the dark. im hoping someone with more experience can chime in.

btw i regularly dose 18g into a 14g HQ double basket without issues. i do see the screw indent but it doesnt cause any issues with my flow or extraction.

I started out with the "nickel test" to find the supposed upper limit of dosing. It still seemed low, so I'm assuming my machine just has a less-than-typical amount of headspace. No preinfusion, normal tamp, 25#

I'll try a wider range of doses tomorrow to see if that makes a difference. I'll try 14g - 22 g in 1 gram increments.

It's just not a screw-indent for me. The screen is caked with coffee and there is a lot of channeling in the shot. I've also been trying the WDT, since it's really difficult to distribute with such low doses without a needle.

I use the filtre's dose: 8gr for an 8gr filter, 14gr for a 14gr filtre, 18gr for a 18gr one.
As coffee ages, and in need to updose to compensate, I'll go, maximum, up to two more grams, if more than this quantity is needed, I take a bigger filter.
Leveling is significantly more difficult with a big filter and little coffee, as the tamper is "buried" deep in the filter and far away from the filter's border, that serves as the reference level.
Normally, due to the filter's (conical) format, tamping also calls for a smaller tamper, as the standard one will not go as deep as required.
With incorrect leveling and tamping, extraction problems are to be expected ...