Greetings Caffeinati,

I've just begun the process of dialing in my new rig, and am keen to network with fellow home-baristas with the same set-up -- i.e. the Duetto II and Vario grinder. I have read many of the outstanding intros and how-tos on the site, and certainly welcome tips and techniques from all, but would like to introduce myself to this subset of users in particular.

Q: Has anyone heard of a kitchen-friendly, objective way to evaluate grind size, and size distribution?

We all have the tools to compare temperature and time (and some of us, pressure), but with so much emphasis on grind... and justifiably so... I'm coming up short on methodology here.

I smell an experiment!

Aaron

Aaron

As a home user, if you have chosen a grinder the most productive thing you can do is to get your dose and shot timing down consistently where you get a drink that tastes good to you. I've dismissed the prospect of having a laser spectrometer in my home. I have taken samples and examined them under dissecting microscopes to visualize grind size but this is qualitative without any statistical comparisons. I did learn that a Baratza Virtuoso produces a more consistent grind over wide sizes then a Capresso Infinity but that was quite obvious and not espresso based but brew size ranges. I'd stick to getting the best drinks you can with your equipment and technique and be happy with that.

The best way to judge particle size is to watch the extraction and adjust grind accordingly. Particle distribution is a function of the grinder's design and manufacturing precision, quality and condition of the burrs, and age and roast of the coffee.

Your best tools if you are diagnosing problems or trying to improve:
- a gram scale for weighing dose
- a dissecting needle to assure proper distribution
- a bottomless portafilter for watching the extraction
- a clock with a second hand (or equivalent) to time the shot
- your palate

And as far as all that goes, since this is all new equipment to you, then the best tool for now would be about 250 grams of patience. It only comes in kilos, so you might as well use it all before going on.

With the last of those (palate) being the most valuable of them.

Hello fellow Canuck,

I've had the Duetto II for almost 2 months and last week I got the Vario. I think I've gotten really close to dialing in the latest batch of Ambrosia and Luna Nuova though I'm still experimenting with doses. So far my best shots with L.N. were at 14 grams.

I don't know about measuring particle size but your post caught my attention because it seems like there is a bit of a "powdery" taste in my shots that I don't remember experiencing with the other grinder. So I wondered if the grinder is producing detectable amounts of dust? I don't know. (E.g. I noticed it this evening with about 14.5 grams of Ambrosia producing 2.0-2.5 oz in 24 seconds.)

Some points that might be relevant:

• I could be totally wrong about what I'm tasting; I'm still relatively new to brewing my own shots and still learning.
• I am single-dosing; popcorning is supposed to be minimal with the Vario but maybe this is what's happening? One of these mornings I'll load 2-3 doses worth and see if there is a difference.

d

Question: is the difference in grind size between a short and long shot detectable by a magnifying glass?

Perhaps this is just some tiredness talking, but I wonder if you could compare the particles to some sort of standard like a white paper with super small precise dots. There would be all kinds of problems because the particles fall in a range of sizes, each type of grinder would vary, perhaps even each machine would want a different grind, etc. It would be absurdly hard to develop.

But hypothetically, if you had a speckled piece of paper with each speck representing the "largest recommended particle size" (for your machine, for a specific style of shot with your grinder), could you carefully compare the specks to some grinds in any meaningful way?

Feel free to say no.

Assuming you could, would you actually need to examine the "average recommended particle size" dots instead?

mini wrote:Question: is the difference in grind size between a short and long shot detectable by a magnifying glass?

One click on the Rocky grinder, as an example, is a change is distance between the burrs of difference of approximately 0.001". Once click on that grinder is approximately a change of 4 seconds of extraction time with Silvia. So it depends on your definition of "short" and "long" but a change of 12 seconds of extraction time (all other things being equal) would be only .003" in grinder adjustment.

... so you would need a microscope

mini wrote:... so you would need a microscope

To get any sort of quantitative idea of actual size and distribution you would also need calibrated sets of spheres of known size. From photos or using digital software you would need to measure a statistically significant number of coffee grounds (representitive of the sample) and control spheres and plot the size and the distribution.

Why not just dial in taste by shot timing and dose variation?