Choosing a Grinder
Originally published: 02/09/2002, last updated 02/01/2007.
This is NOT a grinder review. It is an overview of the most common domestic grinders available to the Australian market as of January 2007. In particular, it is aimed at users of domestic espresso machines, because if you've got a non-superautomatic espresso machine at home, you NEED a grinder. I am not going to try to address the cost and ergonomics of the various machines out there so much as the reasons they work as well (or badly) as they do.
What I AM interested in is the accuracy and repeatability of the grind produced, and how well suited it is to various types of espresso machines. There are some fairly simple physical principles at work in burr grinders. Grind quality depends on 3 main factors.
1) The surface area of the burrs.
2) The sharpness of the burrs.
3) The accuracy with which the gap between the burrs can be maintained during grinding.
(Note that in domestic conical burr grinders the burr surface area each coffee bean is exposed to is large by comparison with flat burr grinders.)
As a general rule, one grinder burr is held still (the STATOR) and one rotates (the ROTOR.) In most designs grind fineness is adjusted by moving the stator closer to the rotor. This is usually (but not always) accomplished by screwing up a threaded burr carrier, again usually the top burr. The quality and heft of this carrier and the accuracy with which the threads hold it in place determine the quality of the grind.
As with my evaluation of domestic espresso machines, I looked "under the skin" of various grinders, and found that there are at most half a dozen burr sets involved. So below is a summary of the ones easily available in Australia, although I've also mentioned USA models where I know the names.
Emide, Gaggia MM, Sunbeam, Breville, Braun, La Pavoni PA (USA).
This particular burr set barely qualifies as a burr set. The actual burrs appear to be made from some sort of sintered metal, and there is nary a sharp edge in sight. Grind adjustment is performed by pushing the bottom burr, motor and all, up against the stator top burr, using a sort of wedge system rather than a threaded carrier. Rather than being sheared, the beans are crushed, resulting in high levels of dust. My frank opinion is that these grinders are totally unsuitable for quality espresso production.
Saeco 2002, G3 Ferrari.
A proper cast steel burr set on a threaded brass carrier, but the burrs are quite small and not as well designed as larger sets (note the gaps.) OK for short term use but they seem to wear fairly quickly. I've seen reports that the Saeco can't grind fine enough for commercial espresso, but had no trouble on the second finest setting.
Solis (All), Dualit , DeLonghi KG100, Starbucks Barista, Bodum.
All these grinders use the standard Solis conical burr set and all (except the Bodum, perhaps) are built by Solis. There is no doubt that this burr set is perfectly capable of producing excellent espresso grinds. Unfortunately the top burr carrier is NOT adjusted using a threaded system but by an inclined plane and wedge system. In my opinion this is less accurate as the top burr has more "play", especially as the grinder wears over time. I have no hesitation in recommending the Solis burrset grinders as a good matching grinder for domestic espresso machines with 53mm or smaller portafilters and pressurized filter baskets, but NOT for machines with larger portafilters and non pressurized baskets.
Grinding fine enough for these machines pushes the Solis burrset to the end of the range, potentially increasing the wear and reducing lifespan, and I simply can't recommend it as a long term match. Note that some of the models listed above cannot grind fine enough for espresso as manufactured, and need to be "tweaked" (internally adjusted) to get the correct fineness. You can find out how to do this at Ken Wilson's UK website, www.kwilson.fsnet.co.uk/coffee_index.htm, as well as much other valuable info on grinders.
Lux, Ascaso Conical, La Pavoni PB, Iberital, Isomac, Sunbeam EM0480 & EM0450, etc.
The one weakness of this conical burr set is that the threaded burr carrier is made from some sort of hard black plastic, however in practice this particular set seems to last as long and work as well as a brass carrier. The oldest model I have in the field is now 10 years old and still performing well, after a recent burr replacement.
Certainly they can grind fine enough and accurately enough to produce excellent espresso on any machine, and do it consistently over a long period of use. The burr carriers used in the Sunbeam grinders are more fragile than those in the Lux type ones, but the burrs themselves are identical.
Rancilio Rocky, Ascaso Flat, Gaggia MDF, Mazzer Minis and so on.
These grinders use standard professional flat burr sets with professional brass threaded burr carriers, and, as you would expect, are fully capable of grinding for professional espresso machines. At this level of grinder (and price) other factors not related directly to the grind come into play, such as doser quality, speed, grind temperature etc.
There are a number of excellent grinder reviews on Coffeegeek (see http://www.coffeegeek.com/detailed/innovagrinder ) and elsewhere, which (in my opinion) do a better job of addressing the "ergonomics" of the various grinder designs and brands than I ever could. As I said at the start, that's not what I was trying to do, my interest is purely in the technical aspects of the burr types and how well they are capable of producing an espresso grind.
Why Do I Need a Grinder?
Freshness: Whole bean coffee stays fresher longer. As soon as you grind a coffee bean you multiply the staling reaction by the number of particles produced, lots in the case of an espresso grind.
Precision: Espresso coffee demands an exacting set of conditions for a perfect extraction. Given a particular espresso machine, you can normally only control your grind, dose and tamp to achieve this. Of the 3 parameters, grind is the most important, followed by dose quantity and then tamp. Coffee is somewhat hygroscopic, absorbing moisture from the atmosphere, so changes in ambient temperature and humidity can have a marked effect on the coffee grind.
Adjustability: Using pre-ground coffee for espresso cripples the ability to adjust to changing conditions. A good shot one day may be only average the next, and undrinkable on the third day. Meanwhile the preground coffee is subject to accelerated staling due to its vastly increased surface area compared to the whole bean. The staling reaction actually changes the way the shot extracts. Without fresh beans and a good grinder it is simply not possible to get consistently good espresso.
Stepless vs. Stepped Adjustment.
Stepless domestic grinders are usually adjusted via a worm gear, and in theory are infinitely adjustable within their range. This can benefit the skilled barista when trying for the perfect shot, but in practice other variables like dose and tamp can swamp the effect of miniscule grind adjustments. Large grind adjustments (for different beans or brewing processes) can be extremely difficult, as can returning to a previous grind setting.
My recommendation for households where the grinder is used for more than one brewing method or the coffee type is changed frequently is to go with a stepped grinder.
Doser vs. Doserless.
The Doser is the cylindrical container on the front of some grinders which receives the ground coffee. Pulling the lever at the side of the doser rotates a set of vaned compartments, allowing the coffee to drop into a portafilter below. On commercial grinders the size of the coffee dose is adjustable so you can get a reliable amount per shot. Domestic dosers are generally not adjustable. In addition, even commercial dosers need to be half to three quarters full to work correctly, which is a lot of coffee to have ground up.
My recommendation is that if you're only making one to two coffees at a time, doserless is better. However, if you have a consistent need to make more than a couple of coffees at a time, a doser saves a LOT of work. This is why commercial cafe grinders have dosers.
