I've had my Vetrano for a month or so, and I've been trying different beans from local roasters. Quite often I notice that my pucks are pretty wet, often with a little puddle on top.

This week I went to a new cafe where the owner has studied with David Schomer and they do latte art. This is the first time I've seen a barista of this calibre and I was watching closely while she did her thing. One thing that I noticed was how dry the puck was when she banged out the PF.

I bought some of their beans that were delivered that day fresh from the roaster, and to my surprise my pucks are just as dry. This is the first time I've had pucks like this since I bought my machine.

Do the beans make a difference or is it just my imagination?

Cheers,

Andrew

In my experience, wet pucks result when the puck does not expand properly through the shot (or during the preinfusion) to fill the space between the shower screen and the puck. A different coffee (more oils?) may help, but I believe it's primarily a dosing and grinding and tamping question. Ultimately, i believe it's a dosing question. Lately i've been varying tamp pressure rather than fine tuning my super jolly. I'm getting pretty accurate at just looking at my dose and grind and feeling the pressure as i tamp to be able to adjust variables on the fly to arrive at a 25-30 second shot (with a dry puck, of course) A wet puck is not bad because it's a wet puck, a wet puck is bad because it means that your variables are off.

I started with a Silvia and for the first month or so I was getting soupy and wet pucks. I think some of was due to underdosing but it must have been technique as well. After a good bit of practice dosing, distributing and tamping the pucks started to dry out and the wet pucks stopped altogether.

I've got a Vetrano now and she's much more forgiving than the Silvia. I think working on technique is good advice. Probably really soon you'll prepare a shot that'll extract well and end up with a dry puck and the wet pucks will end. There's a lot of different techniques to end up with the same result of good even extractions. Trying them all and choosing one that gets you good results and practicing it helps.

It's a dosing and/or grind problem. Some coffees do expand more than others, depending on age of beans, beans involved, etc. By dosing the same amount (visually) you can keep one constant. Alter your grind a little bit finer but dose the same amount. It's a combination of puck density before extraction and puck expansion during extraction (I think ).

Basically, when I get a wet puck, I screw with the grind a bit, and it always seems to work out.

Might be related to grind or dose, last few days I've been switching from if the standard E61 double basket to the LM double, I do get wet pucks on the LM, I'm gonna vary the grind this week-end and experiment a bit.


Sylvain

I assume that a wet puck means either (i) not enough coffee (dosing) or (ii) grind too coarse. So, to solve the problem, the solutin would be to put in more coffee or tighten the grind. Do I have this right, or is it the other way round.

It seems to be happening the other way around for me. The faster the extraction (coarser grind) the dryer the puck seems to be. Although yesterday I had a nice dry puck, and this morning the puck had water on top, and I didn't touch anything on the grinder and I weigh my beans so I get exactly 18 grams every time. I don't know if it matters how long the PF sits in the machine after the pull, but this morning I think it was in the machine a little longer than yesterday.

Andrew

There's a good new article on tampers/tamping on Coffeegeek. I used to get well timed shots with a Silvia but every once in a while the same grind and tamp would get me a ristretto or even choke the machine. I think it had to do with dose, distribution and tamp.

I think when the dose was just on to allow a good puck expansion and the distribution was very even and level and the tamp was level and sealed the edges well the even density and resistance affected the extraction. In reference to the Coffeegeek tamping article a point is made that tamping a full basket only compacts maybe the upper 1/3 or so of the grinds. Below that there may be not a lot of compacting going on so if the bottom of your basket isn't distributed well when extractions gets down there the pressurized water will find a path of least resistance. Distribute evenly, though, and the even density will evenly resist water pressure and most likely end up with a good extraction. That's maybe why some shots start out well but blond quickly and don't show obvious channeling on the surface of the spent puck.

Work on a good dose, even distribution and even tamp to seal up the puck surface and that will probably help.

Is your machine absolutely positively up to temp before you pull your shots. I often see them on cold machines, though don't really know why.
Please bear in mind that most, if not all, of the expansion happens once you finish pulling the shot and the solenoid releases the pressure out of the top of the group.

mrgnomer wrote:In reference to the Coffeegeek tamping article a point is made that tamping a full basket only compacts maybe the upper 1/3 or so of the grinds. Below that there may be not a lot of compacting going on so if the bottom of your basket isn't distributed well when extractions gets down there the pressurized water will find a path of least resistance.

We were discussing Mark's article at our usual Friday espresso get-together, specifically about how force is transmitted through different mediums. Ironically Lino had a meeting later the same morning to discuss the minimum nutation necessary to properly compact asphalt, the same principals applying loosely to coffee pucks. I won't attempt to summarize Lino's explanation, other than to say the multiple angles of attack contribute more to the tighter compaction than simply how hard one presses; this may also explain why Michael Teahan's SCAA presentation reported no significant difference between a 30 and 300 pound tamp.