Indeed, I had thought of rice/grindz as well, but their density and oil content is different, so there's no guarantee that the rice will act the same, as Chris pointed out. Still an interesting experiment that we ought to do on these big grinders--it ought to be at least comparatively interesting.

Speaking of comparatively interesting, I think we should figure out a standard procedure for how to quantify how much rice purging it takes to get all (or almost all) of the coffee out the chute so it flows rice-colored, and then do the same with the coffee beans--how much purging it takes to clear out all the rice from the chute and flow solid brown. I think weighing each of those samples for all the big grinders we can--At least Tom's Major, my Robur, hopefully Chris's and Paul's Robur E's, and my Nino when it arrives next week. I think ultimately that test could be a pretty meaningful one to compare grinders' efficiency at (a) purging stale grinds and (b) switching coffees.

gyro wrote:There are no auger problems as far as I am aware

Ah so it doesn't actually break up any beans around it, just pushed them in whole?

For some reason I got the impression it would be surrounded by a small area of broken beans under the whole beans in the grinding chamber mouth....

Thanks for putting me right on that.

Cheers

Mike

Mike: from what I have seen, the Augur does smash the beans, as I mentioned. However, whether or not this actually causes a staling problem on the scale of fully-ground beans is 100% my speculation. It's entirely possible that it's irrelevant, and that the problem of staleness and the large purging requirement on Paul's Robur E is totally from gradual mixing of the stale coffee with fresh-ground, or something else entirely. Most of this is still speculation at this point.

shadowfax wrote:Interesting notes; I am basing my comments on my friend Paul's Robur E. He's had it for about a year now and he's been dealing with the issue that the first 3 shots of his sessions are always quite sub-par; he thinks he's finally figured out that it's attributed to stale grinds in the path on the Robur E, but it's difficult to tell for sure. I've been suggesting that he start posting; maybe at some point he'll post some pictures of what his grinder looks like.

As has been discussed recently, it seems likely that in a chute full of stale grinds there's some degree of mixing, i.e. if there are 15 grams of stale grinds in the path, it's not necessarily the case that purging 15 grams of coffee through the system will yield in removing all and only those 15 grams of stale grinds.

Suffice it to say, I am suspicious that the Robur E is a low-waste solution for grinding at home. I'm curious how much better the Nino will be. It sounds like it might be significantly better, and I would really like to find out... So I ordered one, "on the cheap." More to follow.

O.K. Nicholas, I'll chime in. I just tried the coffee to rice and then rice to coffee experiment with my Robur E with some interesting results. After grinding all the remaining coffee out of the hopper I poured a generous amount of rice in and watched carefully with the fingerguard removed. With the grinder running, the first appearance of rice was out of the bottom two grids, then quickly and evenly filling upwards toward the top grids as well. Total time was about 3 seconds counting from the first appearance of rice until all rice. Switching back to coffee the opposite occurred. Coffee first appeared out of the top two grids and then quickly filled in towards the bottom, again about 3 sec's. The most obvious reason for this reversal from bottom to top then top to bottom must be due to, as mentioned earlier, the different densities of each. Since my Robur grinds a double (17-18grams) in 3.0 sec's, one could estimate that this is the amount of coffee it would take to displace stale with fresh coffee once that fresh coffee appeared at the chute opening. You would then have to add the weight of stale grinds already in the chute and chamber that was purged before the fresh coffee appeared at the opening. I weighed the amount of grinds left behind in the chamber as well as chute after grinding which equaled a little over 11 grams. Add these two together and you have just shy of 30 grams. Ouch! I speculate that this experiment might not be very accurate, while the displacement of stale to fresh coffee might give dissimilar results with their more similar densities.

Paul, wow! I am surprised that the density difference yields such a different result in terms of how it purges out (rice being much denser than coffee). That makes me wonder if it would be more useful to use Grindz, which I believe is less dense; I believe it was designed to aproximate the hardness/density of coffee, and having used it a couple of times, I recall it being lighter than rice.

In any case, I suspect the test is going to need some revision before the gram numbers that it yields could be a reasonable approximation of the purging that it takes to purge sufficient stale grinds from the system after a long period of idleness (i.e., overnight+). Thanks for weighing in with your findings...

pjones wrote:Since my Robur grinds a double (17-18grams) in 3.0 sec's, one could estimate that this is the amount of coffee it would take to displace stale with fresh coffee once that fresh coffee appeared at the chute opening. You would then have to add the weight of stale grinds already in the chute and chamber that was purged before the fresh coffee appeared at the opening. I weighed the amount of grinds left behind in the chamber as well as chute after grinding which equaled a little over 11 grams. Add these two together and you have just shy of 30 grams.

Thanks for doing this, I think thats quite good to know that there is at least a fairly good purge of the system by a sacrificial seasoning shot. Although the densities are different, if it purged well both ways (ie coffee to rice, and vv) then I don't think it an unreasonable assumption that with equal densities it should do also.

Had a few drinks last night so my head is not as clear as it should be, but if it completely purges the rice, or coffee, in 3 secs, then isn't the total 'stale' coffee going to be around 18 grams as that already counts the weight in the chute (by virtue of clearing it). In other words, if everything has changed from white to brown in 3 secs, then 18 grams of residual grounds? This would tally with my effort (albeit a little flawed) that resulted in 14 grams residual coffee by simply running it until the hopper was empty. I might be missing something here though as I am a bit hazy

michaelbenis wrote:Ah so it doesn't actually break up any beans around it, just pushed them in whole?

It breaks the beans a little, but doesn't do any 'grinding' at all. I doubt the small increase in surface area by the beans breaking in half or quarters has any material effect on staling compared to the massive increase in surface area from 'grinding', if you get my drift.

In mine at least, there are whole beans under the auger as well as a few reasonably large broken pieces.

With my dud burrs, when it choked and didn't feed through, then the auger minced everything in its path as there was no downwards movement. It was basically like a food processor! But thats not the norm thankfully...

gyro wrote:Thanks for doing this, I think thats quite good to know that there is at least a fairly good purge of the system by a sacrificial seasoning shot. Although the densities are different, if it purged well both ways (ie coffee to rice, and vv) then I don't think it an unreasonable assumption that with equal densities it should do also.

Had a few drinks last night so my head is not as clear as it should be, but if it completely purges the rice, or coffee, in 3 secs, then isn't the total 'stale' coffee going to be around 18 grams as that already counts the weight in the chute (by virtue of clearing it). In other words, if everything has changed from white to brown in 3 secs, then 18 grams of residual grounds? This would tally with my effort (albeit a little flawed) that resulted in 14 grams residual coffee by simply running it until the hopper was empty. I might be missing something here though as I am a bit hazy

The three second timing was started once I noticed the first sign of rice appearing at the chute and ended when the coffee was replaced with all rice, not from when I started grinding. Therefore the additional weight of the chute and chamber was added. However, please don't take too much away from this as it was just a rough estimate and not very scientific. Now that my grinder is completely free of any stale grinds, tomorrow I will pull several shots to see if any difference is noted.

Ah, I see, that makes sense. I just had a go on mine... It seems to mix the rice and coffee together for quite some time when grinding the rice (although I had accidentally run it 'dry' beforehand). When switching back to coffee though the change was much faster and 'distinct'. I noticed the coffee coming out the top of the grid first as well when purging the rice with coffee - no mistaking the effect of different density there.

shadowfax wrote:I think we should figure out a standard procedure for how to quantify how much rice purging it takes to get all (or almost all) of the coffee out the chute

1. Grind a bit of coffee to ensure the path is loaded. Use this to verify the grams per second grind rate of the grinder.
2. Remove all beans from top of hopper/burrs with vac. Don't grind with nothing in the hopper.
3. Load up one cup of rice
4. Grind until mostly white grounds exiting chute, remember a little coffee will look like more than it is when mixed with white grounds. If possible, use a pulsed time of 0.5 second to verify timing.
5. Weigh the predominantly coffee coloured grounds. This will give an idea of weight, but will be upset by the higher density of rice grounds.
6. Remove all rice from top of hopper/burrs with vac. Don't grind with nothing in the hopper.
7. Load up with beans again.
8. Grind until its back to almost all coffee out the chute. Again, use a half second pulse.
9. Weigh the predominately white grounds.

Weighing of the grounds will only be useful for a comparison between grinders, since the density of rice and coffee is different. However, the second timing in particular (first grinding of rice may work at a different rate) could be a reasonable approximation of the weight of residual grounds in the system so long as the grind setting has not changed and you know the normal grams per second your grinder runs at.

Thoughts?