It's holy writ: espresso grinders need to be adjusted frequently and precisely. Holy writ is wrong; instead, you only need to adjust the grinder when you change the dose, the blend, or the style of shot (e.g. from ristretto to normale). All other grinder adjustments are a sign of sub-par technique.

How can this be? We all know that a grinder with too few grind settings will produce inconsistent shots, and we all know any cafe where grind adjustments are not allowed will have espresso that sucks. It turns out that frequent grinder adjustment is what economists and engineers call a 2nd best solution, something you do when the best solution is unavailable:

• As the weather changes, as the coffee ages, as the static charges on the grinder wax and wane, the ground coffee becomes fluffier or less fluffy, and also more or less compressible.
• These changes affect the density of the prepared puck.
• So, if you dose by volume, it will vary the weight of coffee you use from shot to shot.
• But the flow rate depends almost entirely on the weight of coffee.
• So if you dose by volume, you will see frequent changes in the shot's flow, and have to make frequent grind adjustments.
• Since these grind adjustments are retrospective and cannot anticipate how the ground coffee characteristics will change for the next shot; volume dosing will always be jittery, both in shot by shot flow rates, and in the compensating grind adjustments.

If you dose by weight, the jitters go away. Instead, the same dose from the same blend will always get you the same flow. Call this the principle of grind-weight invariance.

How do I know this? I first noticed it when I was doing the TGP. I could pencil in the grind settings on the grinders, come back to them four to five days later, and still be perfectly dialed in. You have to be more precise on the weight and the grind adjustment for smaller burrs or flats than for larger burrs or conical ones; but the principle of grind-weight invariance holds. Since then, for the past two years, I've been weighing doses. I've found, without exception, that when dosing by weight, once a blend is dialed in, it stays dialed in.

Consequently, I believe that the overwhelming reason for inconsistent shots in high end cafes is dosing by volume or grind time. Once they find a way to routinely dose by weight, the consistency of the shots will improve tremendously.

I read your previous thread on the subject, and decided to give it a go a little while back. Once I have a blend dialed in nicely at a mid-range dose, I vary my shots by altering the dose in small amounts as I go through a bag. When I pull a new bag out of the freezer, I just lower my dose a little to compensate for the freshness. I have a pretty consistent technique where I just pop the PF basket, grind and dose by eye, and check the weight with a 0.1g scale.

Jim, I agree 100%. Consistency of my shots improved immensely when I started single dosing. Now I can't imaging doing it any other way since I tried timed and volume dosing and it was way too inconsistent.

I have also observed what you are saying about grinder adjustment. My grinder is same or within couple of notches even for different blends as long as I am making same style shots...

Interesting that you would post this....because I came to a similar conclusion a few months ago.

Now I only adjust my grinders when dialing in a new bean or blend, or if I want to change the dose (or sometimes if I go to a different style of basket). Also, now I usually make adjustments in dose weight to alter the flow instead of adjusting the grind setting.

I agree on weighing the the dose each time. The difference in volume for the same weight is noticeable day to day, or shot to shot. The differences when switching beans is amazing some make big fluffy piles, some dense little cones.

But I have to say that I really appreciate the flexibility that a stepless grinder gives me. Once I dial a shot in to where I like it, I rarely have to adjust the grind, but having the option to make 1/2 (or even occasionally 1/4) turn adjustments to get there is great.

Even though it seems like such small adjustments shouldn't make a difference: a full turn of the worm gear is moving the top burr maybe a 1/2" along the threads, which has an impact on the space between the burrs that's imperceptible, I doubt I have hands steady enough to even measure it if I wanted to (especially after a couple espressos).

Thank you Jim, I have thought this many times myself.

I have read numerous times about the "frequent grind adjustments" required by the Mazzer Mini or even flat burr grinders in general, and I simply don't find that to be the case. I rarely need to move more than a notch away from the sweet spot, and that's only when changing coffees, i.e. from a washed to a natural.

TrlstanC wrote:But I have to say that I really appreciate the flexibility that a stepless grinder gives me.

Oh no, I don't appreciate it. I consider this a MUST HAVE for an espresso grinder.

Don't me wrong. I still make adjustments for bean age, etc., just not as much as I once did. And sometimes it's not required at all, possibly depending on how long beans end up sitting in a hopper.

And so I'll quantify a bit, because I actually disagree with the statement that it is only the weight that controls the flow. It is the density, porosity (with volume OR weight) of the puck that controls pressure and flow of extraction. These two quantities just go one step further than simply saying "weight"

I do think you can still get away with dosing by volume, if you tap on the forks to settle. This eliminates the fluffiness variable to some extent. I typically dose by volume and feel (finger strike distribution) but I also get out the scale when I'm trying to be extra-precise.

On the Baratza Vario, I dose by time & weight because the Vario creates a pile of grinds that is much denser than the Mazzers and thus harder to judge by volume.

There is more than one way to skin a cat.

With all due respect, there isn't any other good way.

It's proof to how backward grinders really are that we are even arguing about this. Nobody doses drugs by anything but weight, nobody buys groceries by anything but weight (except count for some fruit -- a grinder that counts beans would work too), and every competent baker weighs rather than using volumes. A doser filled with staled grounds might be accurate to 1/3 gram; but eyeballing the basket, in a busy work setting -- there's no way.

I know you want to stick up for baristas, but this is not the way -- they don't have microscopes for eyes or scales for fingers. To ask for consistent dosing in a busy cafe setting is to ask the impossible; to assert it can be done, is to set up working baristas for failure.

I can't even see how this is up for argument. Except for dose and blend changes, I haven't had to readjust the grinder for over two years. All others who weigh their dose have had roughly the same experience. Therefore, every occasion the grinder is reset in a cafe in response to flow irregularities is further proof that dosing is not consistent.

It's not up to baristas or cafe owners to fix this, it's up to grinder manufacturers.