Wet pucks: Do beans make any difference?

[arossphoto]

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

[popeye]

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.

[mrgnomer]

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.

[John P]

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.

[SylvainMtl]

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

[spender]

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.

[arossphoto]

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

[mrgnomer]

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.

[King Seven]

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.

[HB]

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.

[mrgnomer]

True. I do a NSEW wiggle while applying tamping pressure and it seems to seal the puck much better. Concentrating force at an angle is probably more effective than straight down, I'd imagine, since the force of a straight down tamp would be transferred over the entire surface of the tamper where as tamping on an angle applies the force only on the area of the edge so the force would be greater. Still, according to the findings in Mark's article, tamping with any method or pressure will only compact the grinds so far in a full basket.

I mean if such a low amount of tamping force, 18lbs I believe, is needed to compact grinds for extraction if you tamp continuously as the basket fills then conversely if you can't generate enough pressure with 50 lbs to out do an 18 lb continuous tamp then the 50 lb tamp can't be compacting much of the lower portion of the basket. Intuitively I agree with the articles conclusion and to me it really highlights how dosing and distributing is probably more important than the tamp if you're tamping after filling the basket. Without the know how and equipment to do controlled testing I could never prove anything but from watching extractions and trying to figure out what's going on what I see supports the idea that there's not much compacting going on in the lower portion of the basket.

I guess the next level of control in extraction would be finding a method to ensure even density through the entire volume of the puck from bottom to top or testing how even density extractions compares to varying density extractions shot quality wise.

[HB]

I guess the next level of control in extraction would be finding a method to ensure even density through the entire volume of the puck from bottom to top or testing how even density extractions compares to varying density extractions shot quality wise.

I don't assume that perfectly uniform compaction will mean better extractions, although I have noted many assume uniformity is goodness (e.g., brew temperature, pressure, and now compaction). To look at it another way, no pro barista worries they'll be spanked by a Swift grinder, which arguably has more uniform compaction than any (manual) non-layered compression technique.

For me, it makes intuitive sense that reduced density nearing the exit would result in an overall more even flow rate (but I'm not a physics major or fluid dynamics engineer). I'll bring this up next time I see Bob Barazza, he'll surely have an informed opinion.

[mrgnomer]

I don't assume that perfectly uniform compaction will mean better extractions, although I have noted many assume uniformity is goodness (e.g., brew temperature, pressure, and now compaction). To look at it another way, no pro barista worries they'll be spanked by a Swift grinder, which arguably has more uniform compaction than any (manual) non-layered compression technique.

For me, it makes intuitive sense that reduced density nearing the exit would result in an overall more even flow rate (but I'm not a physics major or fluid dynamics engineer). I'll bring this up next time I see Bob Barazza, he'll surely have an informed opinion.

I'm not sure- how does espresso extract under pressure? It seems to extract from the edges in and from top to bottom. If that's the case it would explain why the first bit of the extraction is dark and dribbles around the center then starts to concentrate to the center, quicken then lighten up. Density at the top of the puck and around the edges would be greater where the extraction seems to start and lower as the extraction works its way in and down. Wouldn't an evenly dense puck extract longer and better given that the rate of extraction/pressure would stay more constant than a puck who's density varied from top to bottom? I don't know, though.

[HB]

Wouldn't an evenly dense puck extract longer and better given that the rate of extraction/pressure would stay more constant than a puck who's density varied from top to bottom? I don't know, though.

Me neither, but here's my layman's thinking: Imagine a copper pipe under pressure with no obstructions. Now bisect it with a porous filter (e.g., a snubber). I would expect the pressure downstream of the porous filter to be lower than the upstream pressure. Now add a second porous filter after the first. The pressure would be highest before the first filter and step down after each filter. Back to our coffee puck, assuming that the amount of solids extracted is proportional to (a) the pressure and (b) flow rate, I conclude that reduced density lower in the puck could be "a good thing" for more evenly distributed extraction pressures.

But it's midnight and I'm exhausted, so take it with a bag of rock salt. Maybe I can convince Lino to machine a basket that can be installed in either orientation (i.e., tamper compression side up or down) and see if it makes a difference in the cup.

[mrgnomer]

Me neither, but here's my layman's thinking: Imagine a copper pipe under pressure with no obstructions. Now bisect it with a porous filter (e.g., a snubber). I would expect the pressure downstream of the porous filter to be lower than the upstream pressure. Now add a second porous filter after the first. The pressure would be highest before the first filter and step down after each filter. Back to our coffee puck, assuming that the amount of solids extracted is proportional to (a) the pressure and (b) flow rate, I conclude that reduced density lower in the puck could be "a good thing" for more evenly distributed extraction pressures.

But it's midnight and I'm exhausted, so take it with a bag of rock salt. Maybe I can convince Lino to machine a basket that can be installed in either orientation (i.e., tamper compression side up or down) and see if it makes a difference in the cup.

Yeah, it was getting late last night. A little late to be thinking about that kind of stuff.

I think your porous analogy makes sense. One thing, though with the pipe there's no back pressure after the filters. In a basket there's the holes of the basket adding some back pressure, I'd imagine, making it possible for the upstream and downstream pressure to stablize. Ultimately even extraction throughout the entire puck could be the goal, I guess. Might differences in puck density lead to different extractions? I mean increased density would result in higher pressure/extraction where as decreased density would mean lower pressure/less extraction. I think I understand your reasoning with the higher density more extraction, lower density less extraction evening out extraction pressure throughout but I still think changes in density might lead to changes in extraction.

Just when you thought espresso couldn't get more controversial or exciting

I just tried evenly distributing and lightly tamping a 1/3 filled double basket then finishing the dose, distribution tamp with a total volume of about 18g. The distribution for the top of the basket was well under the rim so I used my thumb for the Stockfleth's move and tamped normally. The shot poured thick longer and the cup was deeper and more intense. There might be something to compacting the grinds right down to the bottom of the basket- maybe.

[Psyd]

this may also explain why Michael Teahan's SCAA presentation reported no significant difference between a 30 and 300 pound tamp.

Ehm, (true confession time) when I'm in a hurry and the last dose of grinds out of the grinder (usually my shots) is a little light, I might just get out the beans and grind and re-clean the grinder and have the whole process wait, or, like today when I was just out of beans when the dose was light, I might just redouble my efforts on the tamp and hope that it works out to be drinkable. While the shot blonded a bit earlier than a whole dose would have, I did get a nice near-double (about the amount you'd get out of a ristretto) that tasted better than just adequate, it was good, in about twenty seconds.
Now, if I hadn't changed the tamp from my usual thirty to about forty-five (just a guess) I'm sure that this one would have been a gusher. I also know that if I over-tamp my normal dose, it'll take forty-five to fifty seconds before blonding. Am I the only one, or have I misunderstood the statement that there is "no significant difference between a 30 and 300 pound tamp".

[cannonfodder]

Interesting. So if I took the piston off of my tamper, took my dosed basket back to maintenance and used the hydraulic press to smash the coffee down to 300psi, I would have no negligible difference in the percolation I normally get with a 60lb tamp?

Maybe true but I am having a hard time taking that statement at face value.

[RapidCoffee]

Interesting. So if I took the piston off of my tamper, took my dosed basket back to maintenance and used the hydraulic press to smash the coffee down to 300psi, I would have no negligible difference in the percolation I normally get with a 60lb tamp?

Eagerly awaiting the results...

[cannonfodder]

I may try it.

[HB]

I also know that if I over-tamp my normal dose, it'll take forty-five to fifty seconds before blonding. Am I the only one, or have I misunderstood the statement that there is "no significant difference between a 30 and 300 pound tamp".

You understood Michael's claim correctly, and I am equally dubious. Like you, I admit to "modulating" tamper pressure in an emergency, e.g., distracted by the kids, forget a required grinder adjustment for the next shot, and have one minute before flying out the door. I didn't press (ha!) Michael on the point when he brought it up in conversation while leafing through his presentation, but I have to assume there's another factor he didn't mention.

It doesn't surprise me there's some point at which further uni-directional pressure makes little or no difference... that was Lino's point about nutating action and asphalt compression.