Update: Added link for the WDT.
Update 4/8/2009 8:26 am: Added section on dosing and delivery.
Most people say that the number one most important thing in your espresso setup is your grinder. I tend to agree. But the question is: do you need to spend an arm and a leg to get Mazzer or a Rocky?
Now I'm not knocking people who do. The Rocky is supposed to be a pretty good grinder. On the other hand, the reviews are mixed and I've heard plenty of people bash the Rocky. I have no personal experience with the Rocky, but I have to say I wasn't very impressed with the one I saw demonstrated, unlike a lot of Rancilio worshippers.
Maybe that's because I also demoed several Mazzer grinders. Mazzer makes a fine line of grinders, including the most envied Robur. Alas, the Robur is $2,000+ commercial grinder. They do have a "prosumer/low-end commercial" grinder called the Mini. The Mini is $800-900. Okay, so I don't have that kind of money to blow on grinder.
The single most important factor in an espresso grinder is, without a doubt, the burrs. Ken Wilson has a very nice page comparing various burrs.
One that I personally found interesting is the Capresso Infinity. Now I hear all the snobs out there going "that grinder is crap!" Most people online who have knocked the Infinity probably haven't used it.
Funny thing about the Capresso Infinity is that everyone loves to slam it. Why this is, I have no idea. Any statement like "it will only work for machines with pressurized portafilters" or "won't work for commercial-sized portafilters" is just completely wrong. I'm using mine with a machine with a commercial-sized 58 mm non-pressurized portafilter and the grinder can grind fine enough to choke the machine! Other have reported using it with a Rancilio Sylvia or a Gaggia Classic and it works just fine.
The reason I found it so interesting is that, like some grinders costing more than 3-4 times the price, it uses conical burrs made from hardened steel:
Unfortunately, like many cheap grinders (and even some more expensive ones), the burrs are mounted on nylon. Of course this is also the case from the somewhat more accepted (but also in the same price range or slightly more expensive) Baratza Maestro and Starbucks Barista grinders (The Starbucks Barista is simply a rebadged Maestro). the Bodum Antigua, and even the twice as expensive Baratza Virtuoso, which seems to get plenty of love (why? Because it's $200 instead of $89?) I'm not knocking any of these lower-end grinders at all -- from the reviews they all seem pretty good, and, being lower-end, they fit my criteria for this blog.
Here is a picture of Baratza's burrs for the Maestro and Maestro Plus:
The thing about nylon mounts is that this is supposed to cause "burr wobble," which will purportedly cause an inconsistent grind. I have not found this to be the case with my Capresso Infinity, but I've only owned it for about a month or so (and have made wonderful espressos and cappuccinos in that time), so I guess time will tell. I don't expect the thing to last forever, but I can buy 3-4 of these for what an MDF or a Rocky sell for.
Okay, the next thing important about grinders after the burrs is the amount of friction it produces, which causes problems with static and heat. This is the chief reason you can't use a blade grinder for espresso: they spin much too fast, causing a lot of friction, and hence, heat the beans. Beans that are heated lose flavor quickly.
Now here's the thing: most people out there will tell you you need a Gaggia MDF, Rancilio Rocky or even a Mazzer Mini. What's ironic is that when it comes to friction, the lowliest, cheapest conical burrs have the edge here.
All the grinders I just listed are flat burr grinders, or what some call disc burr grinders. Flat burrs spin at around 600 RPM, and some, like the Mazzer Mini, spin at 1600 RPM. Not nearly as bad as a 20,000 RPM blade grinder, but still, these do produce more heat than a conical burr grinder.
The Capresso and the low-end Baratza conical burrs, spin at 420 RPM. Don't get me wrong: other grinder manufacturers, including Mazzer, make conical burr grinders that spin this low. The Mazzer Robur is one such example. The Robur also lists for $2200. I'm sure if you bought one of these beasts (and found room in your kitchen (!?) for it) you'd be quite happy with it and you'd never have to buy another grinder again. On the other hand, unless you're independently wealthy, you'll be saving your pennies for quite sometime to be able to afford to one.
Incidentally, when it comes to static, all grinders have been reported to have some problems with static, depending on the bean. That's because of the friction involved. Of course, the lower speed the motor, the less static. The nylon mountings in the lower-end machines make them a little more staticky, but even the Rocky is known to have some static problems.
As far as clumping goes, from what I can see any doserless grinder, whether the kind that grinds directly into a portafilter or one like the Baratza grinders that grinds into a bin, has problems with clumping. The clumping is a result of the grinds being extruded through some kind of chute, as opposed to just falling out of the grind chamber into a doser, as doser-based models do. This will result clumping, whether we're talking about $100 Baratza or Capresso Infinity, or a $900 Mazzer Mini E Doserless. You can change the grinder, but you cannae change the laws of physics, Cap'n.
The doser on doser-grinders tends to break up clumps and allow for a more even distribution, so clumping isn't really a problem on these grinders.
Clumping is a problem because it can cause your tamped puck to be uneven, which will result in what is known as channeling. Water always takes the path of least resistance, and if there area areas of the puck that are less dense than others, water will rush through resulting in an overextracted shot. Extraction problems like these will cause your espresso to be very bitter.
Clumping can be compensated for, however, with the Weiss Distribution Technique. While not suitable for a cafe because it takes up a lot of time, this technique is fine to use at home. You're not making 6 shots in 10 minutes now, right?
Another big factor is grind adjustability. One complaint about the Infinity is that it just doesn't have enough adjustability. I agree, that, out of the box, the Infnity doesn't have very much adjustability.
Many grinders for the home have stepped adjustability. This means that there are only so many positions that the grinder can be set to. If you don't have enough steps, you don't get enough grind adjustability to fine-tune your espresso grinds. Many grinders, like Rocky, have 40 different settings. The Capresso Infinity has only 16. Some more expensive grinders are stepless, which means they have infinite adjustability.
"Wait! I thought you said you could get the Infinity you keep talking about to grind espresso! Ha! It is useless for espresso!" However, modding the Infinity grinder is actually very, very simpler. Just check out this thread about modding the Infinity to be a stepless grinder. Note that one of the guys in this thread uses his Infinity with a Gaggia (commercial-sized 58 mm non-pressurized portafilter!), which is not supposed to work! And the modder at least claims to be a professional barista. (I know, I know, on the intarwebs, 13-year-old girls are really 45-year-old men...)
Also, even if you aren't willing to mod an Infinity, you can just grind fine enough to choke your machine, and then tamp a little lighter, 10 lbs instead of 30 lbs. In fact, this is pretty standard practice for Italian baristas!
Dosing and Delivery
Probably the least important thing about grinders from the home users' perspective is how the coffee ends up in the portafilter basket.
One thing I discovered about my Infinity last night is that while it has a plastic bin like the Baratza grinders, it will grind directly into a commercial-sized 58 mm portafilter, just like some of the big boys' doserless grinders! The chamber that the plastic bin fits in happens to be exactly the right size for a 58 mm portafilter. I've had this grinder for a month now and I've just noticed this. Doh!
One thing, though, is that I use the WDT, when I put my portafilter basket into the machine, it's got the yogurt cup sitting in it. I think it might be a bit messier if you didn't have the yogurt cup, but I haven't tried it (yet). The thing I noticed about this arrangement is that it way cuts back on the static.
One bad thing about the Infinity is that grinds seem to get stuck in the grind chamber and at the mouth of the delivery chute. I'm working on a mod that will sweep the grounds out of the chamber and into chute.
Putting it all Together
The lower end grinders certain can do just fine for espresso, with modding and/or good compensation skills. Few question the Baratza grinders, and those that question the Infinity just have no idea what they're talking about.
In the next couple of days, I'll talk about low-end espresso machines!