This issue came up in a sifting/sieving thread a while back (starting here) but didn't gain much traction. I'd like to circle back to it now that I'm in full "hand grinder evaluation" mode--hausgrind vs. LIDOs 1 and 2, which reigns supreme?--in hopes that the discussion might shed light on a set of best practices for such evaluation with respect to filter coffee grinders in particular.

Motivation: you have two grinders and would like to identify which one produces a more consistent grind. Or, alternatively, you'd like to determine which makes for a better-tasting cup and feel confident that any difference you perceive isn't due to one grinder not being as well dialed in.

Problem: doing so seems to presuppose the ability to match the grinders being compared in terms of grind "setting" to start with. Loaded term, I know.

In that earlier thread linked above I mentioned one attempt I'd seen to address this sort of problem during the Titan Grinder Project:

RapidCoffee wrote:The samples were prepared by adjusting each grinder to yield a specific type of shot on one espresso machine. In this case, a ridgeless double basket was dosed with 19g coffee, and the grind adjusted to yield a 60ml shot in 30 seconds on a QuickMill Vetrano. After adjustment, three samples were ground on each grinder. Sample size ranges from 10g (1/8 cup) for wet analysis to 40g (1/2 cup) for dry analysis

Doesn't help for brewed coffee, but it's the same general idea.

Anyone have some insight to share?

I notice a lot of eyeballing going on in grinder comparisons--sometimes with the aid of admittedly sexy macro pics--but I'd strongly prefer a more systematic, valid way of measuring grind consistency.

For espresso, same flow from the same dose, basket, machine, coffee is as good anything. The same can be done for pourover; but I've never tried it.

Thanks, Jim. Right, re: pourover I was thinking aloud back in Nov. along those lines, e.g.

jbviau wrote:My first inclination would be to use a consistent-as-possible pourover routine and rely on drawdown time as a guide, e.g. adjust the grinders' settings until their coffee (unsieved) gives me equally long pourover drawdowns and then sieve to compare. Hmm, now that I've written that out I'm unsure if it makes any sense. Little help, please?

Not crazy, I guess!

Thanks for bringing this up again, jbviau. I am in the exact same position as you (trying to decide between the Lido 1/2 and Hausgrind for a grinder in use as a pourover, and interested in a scientific evaluation of grind size).

While it's where my mind immediately went as well, I'm unsure of accurate drawdown time will be. Imagine that you have taken these two grinders and dialed them in to where they finishing dripping at the exact same time with all other parameters equal. Couldn't it be possible that one of the grinders is on a coarser setting but has more fines that are slowing down the flow of water to make it equal to that of the other grinder, making them appear to be on the same setting? How would you control for this possibility if you used the drawdown comparison? (or is this even an issue....)

Maybe there's some way you can ultra-precisely measure the distance between the burrs (or contact OE and Knock to get distances between burrs for each setting.

Just my two cents; keep in mind that I'm very new to grinder science, but very interested.

Each grind is a unique distribution of particles; so there is no way of making them identical. You are looking for the identical setting a central measure like a mean or median.

Using the draw down time is one way to get at a such a central measure. Another way is to take an arbitrary screen, the closer to the average grind size the better, and set the grinds so the same proportion is sieved. The final method is to use immersion brewing (i.e FP) and set the grind so you get the same extraction properties. You don't need to know the units, and you are using the same coffee for the same steep time, so you can equalize with a TDS meter or a refractometer or even oven drying a set weight of the brew

If you want to turn this into a major project, you can do all three methods and see how close the settings are are.

I know for certain that in terms of taste in espresso, I can get two grinders the closest by equalizing the flow, and not by the other methods. But I haven't tried it for brewing.

jbviau wrote:My first inclination would be to use a consistent-as-possible pourover routine and rely on drawdown time as a guide, e.g. adjust the grinders' settings until their coffee (unsieved) gives me equally long pourover drawdowns and then sieve to compare. Hmm, now that I've written that out I'm unsure if it makes any sense. Little help, please?!

CCD (or variations) would be the easiest way to achieve consistency. You can use any kind of filter, whether swiss gold, cloth, oxygenated, or trader joe's paper bags with handles. Get both grinders to result in equal draw down time, then sift each set of dry grounds. When you sift, use the same amount of time for both (e.g. 60s, 90s, 120s, whatever) Make sure to weigh the sifted before and after. Also, inspect the sifted grounds, of course.

One thing I'd urge, try to do at least a one-level blind taste test of the draw-down product, and do several test cases. You'll be surprised with the results. Watch the caffeine intake, too.

Alternatively, invest in a laser diffraction machine doohickey

I'm hoping that someday the http://www.coffeenotes.net/ Android app will be available to do some sort of photographic grind size analysis. I signed up for their Kickstarter last year, but it failed to reach the funding goal, but Greg Mayworm is apparently continuing to work on developing this app for commercial release. Here's a photo that he posted quite some time ago to Twitter:



I would love to use this app to compare grinders, but to dial in grinders to compare the flavors produced for manual pour-over you'd have to equalize the draw down time or go through a lot of iterations with different grind sizes to find the best flavor for each grinder by grind size and pour-over method.

I think the idea of just doing a CCD, with equal draw down time would probably be the easiest way. You are looking for the end result, which one produces a better cup.

I had to go about a month using my Hario Mini as my only coffee grinder, and after finally getting my Preciso back up and going the first thing I noticed was how much finer I could grind with the Preciso to acheive the same draw down time. I don't need to do analysis of the grind of each or sieve one to know that the Preciso is better or that I didn't have my Hario fine enough. The very process of having to grind coarser to acheive the same results shows you the coarser grinder with it's fines is inferior. The use of a sieve is a crutch to help boost a grinder's ability, a PED!

However, you are just going to have to dust off your entire collection of brewing gear and take them all through the paces of each tho and come to your own conclusions. Perhaps you should be ordering a 5lb bag or two of coffee to keep it constant over the evaluation period.

I've done coffee grind particle analysis with a scientific software called "ImageJ" it's free, lightweight, and easy to use.. you can get it here: http://rsbweb.nih.gov/ij/

Having an android/iOS app such as coffeenotes is definitely more convenient, and i too was hoping it got funded, but ImageJ doesn't take that much of an effort, and lets you export the results as spreadsheet format to graph your results..

Check this youtube video for info on how to use it:
Once you establish an average grind size for your first grinder, you basically should just try to match the same average grind size for your second, third or whatever grinders you want to compare to, that's how i'd do it anyway, i'm sure there are other ways, such as particle weight average instead of particle size.

Thanks, I'm going to have to give ImageJ a try. If there's enough interest, this might make a good stand-alone thread.