peacecup wrote:JimS always gets angry when I say this, but for all the fanfare for taste differences among grinders, there are very few objective tests that I've seen. In fact Jim's blind test results are the only ones I've seen.

Roeland, since you seem to know a lot about burrs, and have lots of experience with old hand grinders and Titan class conicals - are there easily observable differences in the grind quality between these two extremes? I.e., can you easily see that the small burrs produce more (or less) fines or uneven grinds? Maybe a comparison between these extremes would shed some light on the more subtle differences between two Titan class grinders.

I'm sorry to say that I know very little about burrs, but I like to ponder about them. By looks, I can't distinguish the grinds. Anyone care to guess which one is the 60 year old hand grinder being forced to grind finer than it's designed to do and which one is a $2000 mechanical masterpiece which is supposedly amongst the finest available?

I actually dialed in the PeDe back from drip by just looking at the grinds. First shot was right on the money flow-wise. Can't say that it was any good, but then again, it didn't taste good from the MC either since the beans are a few days past a few days past their prime.

In any case, when I upgraded to the Faema MC, I found that dialing was less finicky and quicker. Also, my amount of sink shots decreased. But then again, I got better at making espresso by experience. It's hard to make a definitive judgment without resorting to rigorous testing. And that is no fun when you've got testing to do all by yourself. Everybody I know just fears my coffee bar.

It's fairly easy to set two commercial grinders so they flow the same for the same amount and then prepare two baskets for blind comparison. This tyoe of testing will reveal two things:

1. One grinder is clearly better tasting than the other
2. One grinder is even slightly easier to use and set than the other

.

The dominance of large conical is due to reason two: they are much easier to use with multiple coffee, doses or machines. This is true even when you compare them to the very best flat grinders, like the K30. In terms of taste quality, it's much harder to tell a difference. It is clear when you compare them with low end grinders, but not with standard commercial flat burrs like a Jolly or better.

Now, when it comes to hand grinders, most models are very poor for making fine adjustments to dose and grind levels. On lever machines, where you can compensate by changing the brewing pressure, this is not vitally important; but I don't know many people who use hand grinders with pump machines.

Bluecold wrote: Anyone care to guess which one is the 60 year old hand grinder being forced to grind finer than it's designed to do and which one is a $2000 mechanical masterpiece which is supposedly amongst the finest available?

Finer grind is no quality feature at all, nor is it a minimum requirement to qualify for a propper grinder.
To get an idea of the quality of a grinder, a picture / microscopy of grounds doesn't tell a lot, just taste and the TDS.
Even a laser defractometry which is able to determine the so called "median" doesn't give enough clues of the "fines" to have a representative result.
IMHO only the pharmaceutical industry is able to give us some more clues by measuring with their "high roller" equipment.

Terranova wrote:Finer grind is no quality feature at all, nor is it a minimum requirement to qualify for a propper grinder.
To get an idea of the quality of a grinder, a picture / microscopy of grounds doesn't tell a lot, just taste and the TDS.
Even a laser defractometry which is able to determine the so called "median" doesn't give enough clues of the "fines" to have a representative result.
IMHO only the pharmaceutical industry is able to give us some more clues by measuring with their "high roller" equipment.

The point of the photo was mostly to show that the grind of one grinder which is wildly different from another grinder looks the same on a regular photo. With 'finer grind' I meant that the PeDe was used outside its designed grind-envelope. I did not mean it as praise for the PeDe.

another_jim wrote: Now, when it comes to hand grinders, most models are very poor for making fine adjustments to dose and grind levels. On lever machines, where you can compensate by changing the brewing pressure, this is not vitally important; but I don't know many people who use hand grinders with pump machines.

With a scale, it is as easy to make dose adjustments on a hand grinder as it is with any grinder. I do agree with the harder to make fine adjustments. And indeed, a lever machine offers much more feedback on the grind fineness. If I feel that the puck saturates very easily, I will elongate the preinfusion time to compensate flow-wise.

One interesting comparison which might lead to some useful hypotheses re:taste would be to measure the solids extracted during brewing. I did this once in a crude way with a PeDe and Caravel, and found it remarkably consistent - the spent puck of a 16 g dose always weighed 13g when after I re-dried it, i.e., 3g of solids were extracted.

Perhaps with a good scale and careful measurements one could detect differences in solid extraction between top-end grinders? The amount of solids extracted surely has a large effect on taste?

I suggested the PeDe and Faema comparison because the grind quality ought to be worlds apart - perhaps Roeland can dry a few pucks from each and report back on percent solid extraction? It requires little alteration from the usual brewing routine - one need only save the pucks in a dry place until there weight loss stabilizes.

I am trying to find a way to get into a big conical hand grinder myself, but I'm afraid it's still going to be a while.

Bluecold wrote:Not quite. What I wanted to say was that apparently flat burrs can cope just fine with seemingly huge defects in the grinding surface, whereas this topic deals with comparatively minute defects in the grinding surface. This to furthermore illustrate that in the public domain, there is very little understanding of burr technology and behaviour.

Bluecold wrote:Why don't Mazzer and Mahlkonig think this is important for espresso grinders? If they would think it's important, they'd come up with a better mounting mechanism such as the magnetic burr carrier of the Mahlkonig Tanzania/Ditting K805/Marco Ubergrinder?

Getting back to the screw issue on the surface of the flat burrs.
Having the screws to mount the burrs is a compromise of the selected steel + hardening process.
After the burrs are made, they get hardened and to get them back in shape after heating them up for more than 1000°C they need to be sanded.
Without the holes there is no grip / mechanical hold to sand each side of them. (engineering technology wise)
The other mentioned burrs without holes but magnetic haven't been hardened, but maybe just Nitrid coated (CrN) or made of cast steel, which is also an expencive process.
So it is a real compromise of a long lasting surface (hardened) or freaking expencive process and even with a coating, as soon as the 0,003-0,005mm thick (.000011"-.000019") coating is gone the burrs are weak under the coating.
Refitting this system to existing grinders would increase their costs substantially since this system includes high precision parts and complex machining. Apart from the fact that it is patented by MK.

Personally I don't know if direct surface treatment of the burrs (coating,glas-pearl-blasting,etc) gives a more significant change in particle size distribution, than avoiding the screwholes.
Some Mahlkönig burrs cost much more then $1000 for each pair.