Alright, I feel like I've improved my coffee as much as possible by myself, and looking for some advice from the coffee experts now.

I'm using a Mypressi Twist (V1 if it matters, without the spouts, so it's bottomless), a Hario Skerton (stepless mod, and lower burr stabilized with food-grade tubing), and some very (after 3 days, before two weeks) freshly roasted beans from my local roaster (Buddy Brew Coffee in Tampa, FL). I'm using a 54mm Cafelat curve tamper. I've been using stockfelth+nutating tamp to distribute.

I am using a .1gram digital scale, and had my shots dialed in to a 65% extraction ratio.

I'm still getting spritzing (sometimes pretty nasty, sometimes not, but there's always at least a little), and the accompanying increase in astringency in the cup. I've had the coffee as an espresso from the baristas at Buddy Brew (Faema E61 machine), so I know the flavour profile I'm shooting for.

Additionally, I cupped a single origin of theirs (to figure out the flavour profile I was shooting for), and then made an espresso from it, and managed to dial it in, except for that same bracing astringency.

What could I be doing wrong? The espresso is "okay" but not good. It's getting a little frustrating.

The grinds clump some, so I usually give the grinder a good shake or two to break those up before I dump into the basket. I usually dose around 20g (I've tried down to 16g and up to 22g and 20g seems to taste the best), so I have to tap it a few times throughout that step. I do sometimes feel like the coffee falls unevenly in the basket during this step, I thought that the stockfelth moves would take care of it, but might this be a weak point in my technique?

As for preheating, I tend to follow this procedure:

1) Heat water
2) Flush grinder with the sacrificial gram or 5 of beans
3) Weigh out the beans for the shot
4) Pout boiling water into water chamber of assembled twist. Let it overflow a bit. Cap.
5) Grind (3 minutes if I'm especially lethargic)
6) Dump water and remover basket from twist.
7) Refill twist and fill demitasse with boiling water.
Carefully dry basket. Dose. Double check weight. Distribute and level. Tamp.
9) Remove (still full) water chamber from body of twist. Insert basket. Dump top, dry screen and assemble.
10) Pour boiling water into twist. Cap. Dump the demitasse and dry it.
11) Pull the shot into demitasse on scale.
12) Note beverage weight and shot time (for repeating and diagnostic). Enjoy (sometimes).

I will have to try and give wdt a shot. I'd tried at some point in the past and just made a mess without noticing a difference. And I'd really rather learn to distribute without relying on disection needles and yogurt cups...

Spritzing is channeling. Channeling is caused by one of two basic things. Either the distribution is off, or the grind is not adequate. While coffee freshness will attribute to the rate of extraction, you can still get a spritzing free extraction from old coffee. I would concentrate on the distribution to start with. Have you tried stirring the grinds in the basket prior to the Stockfelth? If you do, and you are still getting channeling then I would look very hard at the grinder. In fact, see if your roaster will let you pull a few shots from your mypressi ground from their grinder. You may have to tweak the grind a touch but if the extractions are good and the astringency is gone, you may want to get a different grinder.

Hmm, that might be worth a shot Dave. The grind from the hario seems nice a fluffy and very consistent, but I know that appearances can be deceiving.

I'll also give some sort of WDT a try next time I can sit down and make a few shots back-to-back. I'll report back with the results.

Alright, I tried a bit of WDT with a needle and the spritzing level stayed about the same. The grinds seems fine too, so I'm a lil' bit befuddled. I'll have to bring my twist next time I head to the roaster.

Grant,

I've used an unmodded Skerton with the mypressi with mediocre results. I'm sure it's better with the lower burr stabilized but I don't know how much. The Kyocera CM-45 is a bit better when new, but it doesn't hold its grind setting once the plastic tabs wear down. So trying that may not turn out any better. If you go to a roaster and use their pro grinder, be sure to ask for their patience as you attempt to find the right grind for your TWIST. It may take a few tries.

The problem may not be your grinder, though. Here are a couple other suggestions that could help:

1. Take your dose down to 18.7 grams and grind one step finer on the Skerton. You may need more fines from a finer grind to get the puck to hold together. Tamp at a firm 25 lbs.

2. Do the WDT and Stockfleth (or circular distribution) before tamping. A nutating tamp is not necessary and makes the puck more uneven in my opinion if not done totally evenly. Better just to tamp and twist, IMO.

3. If you have access to a steam wand, use it to bring the water in the TWIST's bowl up to a real boil before pulling the shot. If you are getting an astringent taste, it could be because your coffee is too lightly roasted or your shot is not hot enough, or both. Maybe filling the bowl with boiling water and dumping is not quite enough with the coffee you are using.

In the absence of using steam to heat the water in the chamber, try putting the top bowl of the TWIST (with screen firmly in place) on a hot plate while it's filled with the boiling water. It will continue to heat as you prep your coffee. A perfect hot plate is the "keep warm" plate on a ceramic/glass stovetop. It's hot but not so hot that it will burn the TWIST, at least not on my stovetop! It does keep the whole chamber toasty hot, but try this at your own risk!

Dom

Two small details, if you twist your tamper after the tamp, do so with almost no pressure. The only thing that this accomplishes is to remove stray grounds form the tamper face and sides. Don't let it screw up your puck, literally.

The second thing is, your basket is thouroughly dry, yes? I mean, it's the obvious, but no one has asked yet.

Dominic: I will definitely try dosing down and grinding finer. That sounds perfectly reasonable. I will report back with the results.

I might be picking up tools to make WDT a bit cleaner on Monday, but I have to say that the single greatest improvement in my espresso has been from the nutating tamp, (or the Staub tamp when I had a flat tamper).

And no, I don't have access to either a hot plate or a steam wand at this time.

Chris: Yeah, for the twist, I essentially spin the tamper on the bed of coffee with no downward force (other than gravity). And yeah, I dry the portafilter baskey carefully before dosing.

EDIT: Taking my dose down to 18.6g or so didn't do much. Though I need to fine the grind up a bit more to be sure (I ended up pulling 32g of espresso - the same as last time, which threw of my extraction ratio). I'm just getting four or five tiny, brief sprays from the basket. Just a few drops sometimes. Everything else looks good. The espresso looks pretty good, it doesn't taste half bad, but I want to kick this.

Sounds like a conundrum. The only thing I can think of is to fix the dose at 18.5-19g and make the grind finer each time until it doesn't spritz any more. At that point if you are getting your shot in less than 40 seconds and if it doesn't taste bitter due to the amount of fines, you are doing okay. If none of that proves satisfactory it's time to try a higher end grinder.

Your extraction ratio may he higher than you think despite the lower dose. The total dissolved solids should increase with finer grind and longer extraction. I guess you can't know for sure without a refractometer of some sort.

But at the end of the day, if taste and mouthfeel are okay, then it doesn't really matter.

Dom