A quick little post about "head room."
That's the space you leave above the coffee puck after tamping grounds down in the portafilter basket.
A lot of people are anal about weighing beans before they load their filters. Then that total amount has to go into the basket. Pro baristas especially are taught this, because in a shop "consistency" is a premium. You want people to "know" what a latte is at your particular shop when they come back next time. Weighing beans helps with churning out similar shots. (Of course it also helps with "portion control" if a shop owner is trying to carefully minimize the coffee they're going throughb every day. Luckily most of us at home don't have to worry about that!
Confession. I don't bother to weigh my beans in the morning. This, despite having been seriously told by a high powered "industry professional" once that weighing beans was, "The most important part of making espresso."
I'm not going to argue about that here. The last thing I'm aspiring to be is an "industry professional!" I happen to actually LIKE variation and "surprises" when I make espresso in the morning. "Mistakes" and accidents have arguably taught me more about making espresso I like than any "industry professional" probably ever could. And feeling like you're working on and assembly line in your own house, takes a bit of the fun out of the espresso making experience for most people. At any rate, being loose with my "process" has led to the personal discovery about "dosing" I'm trying to talk about here.
Because, in this non industry pros opinion, it's actually MORE important to leave the right amount of space above your puck, than it is to try to cram in a specific amount of carefully weighed coffee.
Why? Because the flow of espresso your shot is so important.
When you fill a portafilter all the way to the top, tamp it down, and then add even more coffee trying to cram as much as you can into your portafilter, under the assumption that "more is better" (something I once assumed myself) you're much more likely to have to end up grinding coarser to pull a shot. And have WORSE extraction (i.e. "wasted" unextracted coffee from a spent puck tossed in the compost.)
Believe it or not, a grind that seems "too fine" or even "chokes" your machine so much that you can barely get a shot to pour, will actually flow ok if you leave more clearance on top.
This is partly due to a mechanical phenomena that is easy to ignore. When you lock in your portafilter, you are actually screwing it UP into your group. The harder you push the handle over, the HIGHER the coffee bed is going up into the group and even into the screen. In a lot of machines, especially "home" models, this oftern means people are pushing the coffee puck up into the shower screen, blocking it, and compressing the puck even more than you tamped!
There is also obviously some kind fluid dynamics going on that is over my pay grade, and only an engineer could explain properly, about water flow. I can't explain the physics of it. But trust me, it matters.
So when we say at VoltAge110 that, "Espresso making is way more like a Science Project than we ever expected," this is one of the (often ignored) "variables" you need to play with on your particular machine.
Groups can be very different. Even ones that look similar (like an E61) may have the shower screen higher or lower relative to where the portafilter finally locks in than others.
The obvious starting place is to use the "bold trick" of looking for a pattern (from the shower screen) or "hole" (from the center screw/bolt holding the screen in many machines) in your wet puck after pulling a shot. (Or attempting to pull a shot!)
If you can see the holes from the shower screen/bolt in the coffee puck, you may be "overdosing" your portafilter. You're pushing your coffee up into the screen.
Remember it's hard to get great espresso crema without the right grind. Usually that means on the fine end. And you can grind finer by leaving some "head room" above your puck.
The bottom line? "EXPERIMENT."
As with so many aspects of espresso making, you just need to play around and try different stuff with your machine. Once you figure out how to get close to pulling a shot you like, change things up a little just to see how "tinkering at the margins" can make differences that you can actually taste in your cup.
In terms of what we're talking about with "dosing," that means try grinding a little coarser and tamping harder. Or grinding finer and dosing less. Just try leaving some more head room and see what happens.
The recent "scientific" test at a university that "proved" a shorter shot (like 15 seconds!) with a coarser grind actually "tasted better" to most people, than the traditional 30 second shot with a finer grind, got a lot of attention.
What that really "proves," is that you should experiment on your own. Because it doesn't matter what "most people" think. It matters what you like. It's your machine, and your taste. Don't obsess with "experts" once you get comfortable pulling shots. Figure out what YOU like. (This extends to things like bean roasts and brew temps as well, but those are topics for another day!)
Been thinking about writing another short entry on "single" versus "double" baskets, after recently discovering a single basket (which I'd avoided since day I got my first espresso machine as "obviously too small") actually can make a really nice shot. And save some expensive coffee!
That epiphany obviously goes with a discussions "dosing," but with the basket size, it's probably more about how MUCH espresso you want out of a single pull, and how you're going to consume it.
Like if you want a straight shot, or a Cortado/Gibralter, a single basket might be the way to go. Check it out! If you're like me, you probably have a single basket you've never even used!
And finally, dosing, or not "overdosing," matters even more with lever machines. Electric pump machines, especially those with rotary pumps, can really ramp up the brew pressure and force water through some pretty fine grinds, while the lower pressure from a spring (especially the tiny springs in "home" lever machines) really require a much coarser grind. Again, "experiment." I've had spring groups I almost gave up on getting "good crema" from, only to finally hit the "sweet spot" with a magic combination of correct grind and dose, and have beautiful crema suddenly appear from machines I thought were incapable.
So take a Saturday morning out and play around with dosing. You might be pleasantly surprised at the results. You might not only pull better shots, but save bsome crazy expensive coffee as well.