For the last three years, I've been urging people to experiment with their dosing, trying lower and higher weights of coffee. I was (slightly) wrong; I should have been urging people to experiment with grind settings, trying finer and coarser grinds.

Six of one, half dozen of the other? Not really. Suppose you had a great shot yesterday at a certain grind and dose. The next day, the shot chokes or goes too fast. Here's my argument: change the grind and keep your dose the same, and the shot will no longer be great; keeping the grind the same, and change your dose, and the shot will stay great.

I'll illustrate this with an example; and then make an argument on why this is so.

I'm comparing roasts of the same coffee with Ken Fox. Today I was comparing the Agua Tibia, a Fraijanes we got from SM. The roast color levels were close to the same, both whole bean and ground, indicating functionally equivalent roast profiles. When the coffees first arrived, the grind settings were also the same. But today, a typical air versus drum roast difference appeared -- put the beans on a cutting board, and slice them with a chef's knife, the drum roasted beans tend to shatter more than slice, while the airroasted ones slice more than shatter. This means the drum roasted beans created more fines and the same dose and grind flowed slower than those from the air roaster.

As it happens, Ken's drum roast flowed right, and tasted like Kirsch and Kahlua; while mine flowed fast and tasted sour. The Kirsch and Kahlua thing is the reason we bought these beans. I might have screwed up the roast, but first I needed to make a proper shot. When I tightened up the grind, and maintained the same dose, what I got was overly bitter. When I raised the dose to get the right flow, and kept the grind the same, the shot tasted as it should.

In espresso extraction, the flow rate is largely determined by the amount of fines in the puck, while the extraction rate is determined by the average size of the coarse particles. When you tighten the grind, you do two things: create more fines, slowing down the flow, and make the average size of the coarse particles smaller, raising the extraction rate. This means that if the flow rate is wrong, and the extraction rate is right, changing the grind will make the flow rate right at the cost of screwing up the extraction rate. Once the extraction rate is right, the grind setting should be sacrosanct, and you should control the flow rate by changing the dose.

Makes a lot of sense Jim, for sure.

Ive been doing this, but I suppose without realizing "why". For instance, when I open a new bag, lets us Black Cat Organic for an example, Ill start out with a dose of 19gr.. Thats the dose I want to use for this blend. So, Ill tailor my grind setting to that dose, for the shot Im after. Now, the Major doesnt really need adjustment for about three days at a time, but as the coffee ages, changes need to be made. And I make those changes in the dose, whether it be up or down, and its usually going down some. By the time I was done with the pound, I was dosing about 18.4/18.5gr

And here all this time I thought I was just being lazy. Good to know I was also being smart

It's a doddle with a 0.1s timer. [ with the proviso that one runs a short clearing grind and clears the chute ]

Makes sense, but shouldn't the title be "Dose, not Grind"? Also, the first paragraph seems to be saying we should experiment with grind, while the rest of the piece talks about varying dose. Can you clarify?

When the flow rate goes bad, how much dose adjustment would you try with each iteration? .5g?

I guess the limiting factor on adjusting the dose is headspace. If you need to go up in dose, but that will cause the puck to smash into the shower screen, then it won't work. Perhaps this is an argument for not cramming huge doses into double baskets, or at least leaving enough head room to increase the dose if necessary.

What I'm saying may be too simple to understand the first time around:

Once you find the best tasting dose and grind setting for your coffee, keep the grind setting the same and vary your dose to keep the flow and timing correct, rather than the usual method of changing the grind setting.

This advice assumes you are varying the dose to optimize taste as a matter of course. If you are not, go back to espresso 202.

I've been pretty compulsive with my digital scale to make my dose constant while adjusting my grinder as needed. I will give this method a try and see if my drinks become more consistent. I must say that the drinks do vary somewhat though I try to keep things the same from day to day. Perhaps this is why though we will see.

Question- for those of you (Jim?) dosing directly without weighing for each shot are you really that precise about changing the dose up or down?

So, if I understand well. If my shot time is right, but blond early, I should coarsen the grind and raise the dose to keep my shot time right? If then, the dose needed hit the screen, I should consider roasting darker (more fines?) or changing roasting method (air bed vs drum?)

-Hugo

HugeOne wrote:So, if I understand well. If my shot time is right, but blond early, I should coarsen the grind and raise the dose to keep my shot time right?

I'm not giving diagnostic advice here. I'm not telling you how to make a bad shot better. I'm talking about keeping good shots good. Do this by keeping the grind setting fixed and adjusting the dose to counteract variations in flow rate.

About your scenario: I'm guessing you mean something like the flow rate being right, but the shot goes blond after, say 18, seconds. So your shot ends up too short in volume and too fast in time. You can keep the rate of flow the same either be coarsening the grind and upping the dose, or tightening the grind and lowering the dose. Either may be the right thing to do. If the grind is already too coarse, it blonded because it didn't fully extract, if the grind was too fine, it blonded because it finished extracting too fast. You can tell by the taste.

Varying dose may be the way full dosers are handled in Italy. If the flow changes due to humidity, etc, it's too late to change the grind setting, but one can click the dose volume control knob inside the doser and change the dose 1/3 gram or so per click.

another_jim wrote:In espresso extraction, the flow rate is largely determined by the amount of fines in the puck, while the extraction rate is determined by the average size of the coarse particles. When you tighten the grind, you do two things: create more fines, slowing down the flow, and make the average size of the coarse particles smaller, raising the extraction rate. This means that if the flow rate is wrong, and the extraction rate is right, changing the grind will make the flow rate right at the cost of screwing up the extraction rate. Once the extraction rate is right, the grind setting should be sacrosanct, and you should control the flow rate by changing the dose.

Great post, Jim. I'm going to have to spend more time with this.

BTW, are you saying that drum roasts always produce more fines than air roasts, or is that just true for you and Ken?