# laser particle analysis - group project to understand grinders a bit better



## dsc (Jun 7, 2013)

I've had this idea for a while and with the new year approaching I thought it might be fun to finally do something with it.

A while back I was looking for a lab which can do laser particle analysis to try and understand grinding a bit better. I've dropped Colonna & Smalls an email, they passed me onto Chris Hendon, who then suggested contacting Erol Uman at Meritics (http://www.meritics.com) , which is a company specialising in particle characterisation. Erol and I talked for a bit via email and eventually agreed to meet up for half a day and do as much analysing as possible, all this in exchange for £200 (which is mighty cheap btw). Due to time constrains on both ends, this never came to fruition, but I still think it would be rather beneficial, especially if a large enough sample pot was supplied.

As sample prep takes time and the fact that I might actually have to take a day off work to take the grinders over to Meritics HQs, I was curious if anyone else would be interested in chipping in and splitting the costs in exchange for full access to the analysis results? At one point I was contemplating getting @Glenn involved and making this into a forum wide open access kind of project, but I'm not sure if that's possible.

If anyone has any ideas on what might work in this case, or is simply happy to contribute, drop a reply below and we can at least assess the interest.

T.


----------



## the_partisan (Feb 29, 2016)

I'm happy to make a contribution. How many grinders do you think you can analyse in a day? Me and @MWJB already made some effort with this using Kruve sifter: https://docs.google.com/spreadsheets/d/1cYpaG-4eNmhRxdgctOl0atZnw6nEK80Z68FR9Cy1fjA/edit#gid=0


----------



## dsc (Jun 7, 2013)

Much appreciated @the_partisan, I'd say perhaps 3, more would probably be pushing it, although it depends how it's ran, whether we send samples in, or take the kit over and have a "live" session in the lab (which from what Erol was saying would be better as you avoid sample compression).

We could do a large flat espresso grinder vs conic vs EK43? Here's a list of things which I think would be nice to find out more about:

- single dosing vs hopper dosing - how it affects distribution, this is easily doable on all grinders

- speed vs distribution - this would currently only work on the ZR

- bean feeding vs dose drop - easily doable on all grinders

- alignment vs distribution - doable on all grinders, but would require a lot of time to set up

If anyone else has any more ideas add them below and we can discuss further.

As for the Kruve I can't see it working for espresso as the fine filters clog up too quickly and it takes too long to clean them.

T.


----------



## MWJB (Feb 28, 2012)

I'd be happy to chip in.

Speed vs distribution seems bit esoteric, considering you can count on one hand the number of grinders where this can be adjusted? Isn't this really an area for manufacturers to work on?

Single dosing vs hopper? What would be the metric here? It's been done before but results were inconclusive/showed no clear difference.

The most realistic test would be to establish what was a realistic expectation for the different burr type/sizes, when used in the same fashion (hopper, or no/same brew ratio & best tasting EY)? For the mighty few plots available publicly, there doesn't seem to be any basic definition of 'normal'?

Kruve can be used at the coarser end, larger meshes (also easier to clean), to mark the larger cut-off points, but can't tell us anything about average grind size & smaller end for espresso. Also, people have them in their homes & they don't cost money/days off/lab time to use, so maybe a couple of minutes shaking might show some correlation that might prove useful between the LPA plots and a Kruve sieve (even if it's just the 800)?

Alignment issues - again, most folk probably don't have a clue as to how to go about aligning their grinders, nor any idea what typical factory alignment tolerance is, I don't know how useful it would be to watch folk disappear down rabbit holes aligning their particular grinder.


----------



## fluffles (Sep 4, 2012)

I'd be interested to see distribution graphs at both espresso and brewed settings and what variation there is between grinders and also within the same grinder


----------



## dsc (Jun 7, 2013)

Some more info and reasoning behind what I wrote above:

- Speed vs distribution - the whole idea is to run the same dose and bean through the same grinder at different speeds to see how that affects distribution. I believe that burrsets are made to be ran at specific speeds, or at least a speed range and I've seen some evidence of this in the experiments I've done so far, so more data would be helpful here. At some point it in the past it was assumed that slow grinding is better than fast grinding and it would be good to either confirms this or bust the myth.

- single dosing vs hopper - there's a huge difference in what settings needs to be used for single dosing vs hopper. I'm curious if the particle distribution is the same if you compensate for the method (ie. run the grinder finer when single dosing) or whether you get two different distributions. I do think that single dosing produces different particle shapes, which of course LPA won't pick up, but there might be more difference in the sizing for example

- alignment vs distribution - I've seen many statements re alignment and how it doesn't affect much, so proving how tight the link is would be good, especially since it's possible to measure misalignment, so you can introduce a known error and test the output.

Brew vs espresso might be a bit harder as I can only really do espresso well, brewed isn't my daily thing. Generally it mighty be tricky to test the grinders in the lab without an ability to brew the coffee to double check the settings, so perhaps postage is the only way out of this (ie. brew at a given setting, confirm taste wise brew is fine and grind a sample). On the ZR I can easily go from one setting to another as it's repeatable, but on a Mazzer for example I'd be going in blind as the scale on the collar is pretty much useless.

T.


----------



## MWJB (Feb 28, 2012)

dsc said:


> Some more info and reasoning behind what I wrote above:
> 
> - Speed vs distribution - the whole idea is to run the same dose and bean through the same grinder at different speeds to see how that affects distribution. I believe that burrsets are made to be ran at specific speeds, or at least a speed range and I've seen some evidence of this in the experiments I've done so far, so more data would be helpful here. At some point it in the past it was assumed that slow grinding is better than fast grinding and it would be good to either confirms this or bust the myth.


Grinders that work run from ~240RPM to ~1700RPM. Flats use higher speeds to evacuate the burrs. We (the public) have virtually no choice in RPM. If slower speeds result in better flavour from cooler grinding, we may not see any evidence of this from LPA...we'll just see what the grinders grind.



dsc said:


> alignment vs distribution - I've seen many statements re alignment and how it doesn't affect much, so proving how tight the link is would be good, especially since it's possible to measure misalignment, so you can introduce a known error and test the output.


I haven't, from memory, seen any statements saying alignment doesn't matter. I've seen a few saying the EK needs to be aligned to 10um parallelism at the finishing area, but not anything to disclose what typical factory alignment is, or reasonable tolerance, or any LPA plots to show the difference. So, I'm just not sure what would be a realistic known error. I guess I'm asking what is the benefit to the community from this, when means of measuring tolerance & adjusting then have to be worked out..."Your grind could be better, it might not, either way we're not in a position to help you determine that, nor to fix it"  I've no doubt it matters at some point, just for 99.9% of folk it's going to be pretty much moot.

I like charts, so I'm still in in terms of contributing  But I'd say look at all the plots available online, what have we really learned from any of them, other than the EK goes finer/makes less big chunks at espresso settings?

I'd also be happy to supply samples of brew grind.

I appreciate my thoughts on the matter aren't as sexy as some of the others, but information you can't use doesn't help anyone and more often than not becomes fuel for more myths. If this is grinder research, why are we doing it, not the manufacturers who have LPA equipment in their factories (they probably have done it)? Wouldn't it be better to give folks useful tools to sanity check & improve their coffee at home (I think the hopper/non hopper & maybe even different burr size/sets could do this, if particular trends are shown).


----------



## dsc (Jun 7, 2013)

MWJB said:


> Grinders that work run from ~240RPM to ~1700RPM. Flats use higher speeds to evacuate the burrs. We (the public) have virtually no choice in RPM. If slower speeds result in better flavour from cooler grinding, we may not see any evidence of this from LPA...we'll just see what the grinders grind.


I'm simply curious what the effect of speed is on LPA and I want to clash the results with heavily unproven statements that slow is better to clear that up for once.



MWJB said:


> I haven't, from memory, seen any statements saying alignment doesn't matter. I've seen a few saying the EK needs to be aligned to 10um parallelism at the finishing area, but not anything to disclose what typical factory alignment is, or reasonable tolerance, or any LPA plots to show the difference. So, I'm just not sure what would be a realistic known error. I guess I'm asking what is the benefit to the community from this, when means of measuring tolerance & adjusting then have to be worked out..."Your grind could be better, it might not, either way we're not in a position to help you determine that, nor to fix it"  I've no doubt it matters at some point, just for 99.9% of folk it's going to be pretty much moot.


The whole idea is to find out how bad the misalignment can be without having too much effect on the distribution as this is not really known at this point. Again there's discussions where people ask whether for example 0.05mm misalignment is bad or how bad hand grinders are for espresso as those quite often suffer from misalignment as well (having no support for the lower bearing), at this stage no one really knows, so minimising misalignment seems to be the only reasonable idea.

Another thing I skipped altogether is that any grinder which is used in the study would need aligning as otherwise you don't know if the differences in LPA are from different burrsets or whether it's because one grinder is more aligned than the other.

I'd say the more we can test the better, if there's limited time and money we can prioritise certain tests of course.

T.


----------



## the_partisan (Feb 29, 2016)

I would be curious to see something like the distribution of Ek43 vs Feldgrind both dialled in for filter. We can then correlate the Feldgrind results to our Kruve results.

How does the actual measurement process work and how long does it take? Do you just put in a sample and get the distribution results?


----------



## dsc (Jun 7, 2013)

Some info on the process alone:

"Transport by royal mail will expose your samples to vibration based compaction and large temperature swings. This may cause particles to bind to one another forming lumps or agglomerates. My sizing instrument will separate agglomerates that are weakly bound and this usually is not a problem for coffee but to be precise and "forensic" about the process you need to be aware that transit effects are an added variable that is not included when beans are ground and used in a retail coffee shop. Agglomerates appear on the reported size distribution graphs as low magnitude peaks to the right hand side of the main population. I use microscopy to tell me if such peaks are agglomerates (made of lots of small particles adhered together) or if they are just large discrete particles that are poorly ground.

Re the number of pots and combining enough for 6 analyses (6 teaspoons) into 1 pot. Combining is OK, in fact what's probably best is to put a known constant mass of beans into the feed hopper of your grinder and collect the whole output of grounds into 1 pot. I'll then either sub sample 6 spoons from each pot or simply run the entire pot full through my instrument. By running the entire pot through there is no requirement for sub sampling thereby eradicating that source of statistical anomaly.

Compressing the grounds is not a good idea unless "compression effect" is a parameter that you wish to specifically evaluate with respect to agglomeration. To implement it into the evaluation means we will be attempting to study 2 variables at once, ie, grinder settings and compression simultaneously, this is not good science.

Plan of action: Produce ground samples using enough beans for roughly 6 teaspoons of ground powder. Choose a weight of beans that yields this amount and then always grind the same mass of beans for all of the grinder settings to be evaluated. Place the entire grinder output for each chosen setting into 1 airtight pot and label it. Send the pots by post and the lab will either run 6 samples from each pot (after tumbling each pot to homogenise the contents) or run the entire contents, which ever is deemed best. Whatever method is picked will be replicated throughout all analyses.

Re number of samples the lab can process in an afternoon, the work will proceed with a maximum throughput of around 15 tests per hour."

As you need 6 samples taken per analysis, and speed is 15 samples per hour, you are looking at one full analysis per 24mins, so lets round up to 30min and say that in an hour you could do LPA on two different sample pots which in effect gives you one full comparison in an hour.

T.


----------



## Glenn (Jun 14, 2008)

Keep me posted - keen to find out more


----------



## martyrdon (Dec 13, 2016)

Oh this is funny. I work in a Sand Control lab and I do LPSA tests quite a lot and I've worked a little bit with Erol! Meritics are good people and I'm sure they will be great to work with!


----------



## dsc (Jun 7, 2013)

@martyrdon small world







I'm guessing sand is easier to analyse as the particles are rather round, whereas with coffee you can have all sorts of shapes which is going to have a negative impact on the results.

Erol is having a think on how to plan this well, so for now we all have to wait patiently.

T.


----------

