K7 wrote:From what I've seen on Internet and my own Specialita, +1.5 from true zero for lighter coffee is perfectly normal.

Having to grind right near touching point (for normal double shot, I assume) is abnormal. But the operative phrase here is "on my current beans". If this happens with only this coffee, maybe the coffee is stale or compromised in some way (exposed to too much humidity). I would try another freshly roasted coffee before assuming the grinder needs adjustment.

If you use the grinder with hopper, the exist pathway needs fairly regular cleaning IMO, especially for darker oily roasts. I single dose with a bellows partly because I don't have to clean as often (puffing keeps the chute cleaner), but I still clean it every month or two.

I do use it with the hopper although I never fill it much and blow air/tap it frequently to make sure nothing gets stuck. I've been exclusively using medium to medium roasts (I'd say anywhere from 3 to 6 out of 10 on a magic roast scale ) Always grinding for a double, 18.5g on the stock Breville Dual Boiler basket (with naked portafilter). Very little clumps, always using a WDT and rarely see major signs of channeling.

The current beans are 'optimal' as were the previous ones which gave me even more grief (those however seemed like an extremely light roast to me) ie, 10 days post roasting. I'd say those are about a 4-5 out of 10 on the roast scale. I'd say I'm grinding them at roughly +0.75 . On that topic is there such a thing as a 'too light for espresso' roast ? I was under the impression that with long pre-infusion and extra fine ground anything was doable but maybe I'm just going a little too crazy.

Maybe adding the shims would bump things to the proper place in the end. I'm glad to hear from different users though, that's quite helpful in narrowing the issue if there is one.

Yeah I think +0.75 is within a reasonable range for light roasts if you are going for long PI with very fine grinds. I drink light roasts almost exclusively these days and I'm at around +1.5 for most of them, but I'm not doing long PI (I used to, but not anymore) and my pressure maxes out probably ~6 bar. With long PI and higher pressure, I'm not surprised you are grinding finer than me, especially if it's one of those light roasts like Kenyans that tend to produce little fines to provide puck resistance.

Burr alignment is probably still worthwhile if it looks like way off.

You bring up an interesting point so.. I'm derailing my own topic but is there a correlation between PI time and grind size then ? I was always under the impression that long PI and fine ground was the way to go for lighter roasts ? I'm going 25 seconds PI and maintaining a pressure of roughly 7.5 bar at +0.75 grind size. I always thought that shorter PI meant higher risk for channeling with lighter roast. Must have gotten that wrong Still learning!

Astralmind wrote:You bring up an interesting point so.. I'm derailing my own topic but is there a correlation between PI time and grind size then ?

Of course. When grind is too fine for a given puck thickness, it chokes the machine. Without long PI, you cannot extract. With long enough PI, it softens up the puck and you can then get some flow. Long PI is a mere necessity for extra fine grind, not a goal in itself.

I was always under the impression that long PI and fine ground was the way to go for lighter roasts ?

Like Jeff said above, light roasts need fine grind. Problem is it's often too fine for the puck thickness of typical triple dosing in the US (>=18g). Long PI is just one trick to work around the grinds being too fine. Another popular trick is to use a faster flowing basket like VST. Yet another popular approach is to utilize a grinder that produces less fines for the same grind size. They all share the same goal of working around the choking problem.

But there's a simpler approach to this: stick with double (14g) or maybe even a bit lower. For the same grind size, you don't have the choking problem to begin with! That's what I do.

I'm going 25 seconds PI and maintaining a pressure of roughly 7.5 bar at +0.75 grind size.

Yeah 25sec is pretty long and aligns with very fine grind you are using. I've played with long PI, and maybe it's just me, but I found many coffees don't taste as good with long water contact time. YMMV.

I always thought that shorter PI meant higher risk for channeling with lighter roast. Must have gotten that wrong

Yes, higher risk of channeling. Puck prep needs to be good, but I found it manageable after a while with the Mignon. Also, for light roasts, I found the bottomless pour doesn't need to look very pretty to taste good. It helps that I have a manual lever so I can adapt the flow/pressure on the fly in response to channeling. You might try shortening PI time (20, 15, or 10 sec) with slightly coarser grind and see how it works out. Maybe use even lower pressure like 6 bar just for light roasts to prevent channeling.

Still learning!

Aren't we all here lol.

Thank you both for the replies, much appreciated!

I usually leave my tomato set to 203F (can't believe I'm stuck in F when speaking of liquids even though I'm from Canada...but somehow my brain is locked in) for most of the beans I use as they are medium going on lighter, usually. Did push to 205 for the lightest with a good result.

I'll definitely look into shorter PI and slightly coarser grind. As for smaller shots, my wallet would certainly thank me but I'm a terrible sipper and need a bit of content in my cup I went for the super long PI strategy regardless of the roast after reading all I could find on the BDB modding and profiling. I've given up on the Slayer approach for now (ironically started off with it) but stuck to PI until beads form on bottomless or needle moves a bit. Depending on the beans it usually goes anywhere from 15 to 30 seconds. Ultimately, I liked this video from Slayer to make up my mind about PI vs extraction time balance based on roast. http://www.youtube.com/watch?v=3nnK0paSulc On the BDB I've set the PI to the lower power setting of 55 which is close in flow rate to their suggested medium roast (can't go any lower unless I properly mod it).

100% right that lighter roasts look pretty bad on the bottomless no matter how my puck prep is but I've accepted that fact and stopped staring at the pour. As for the puck itself I certainly won't pretend to be a world class barista puck prepper but I think it's 'not a problem' after 4 months of obsessive attempts. WDT, force tamper, the Mignon itself is a good grinder (when adjusted!) etc.. fluffy even and no signs of obvious channeling. I recall my first attempts with a bottomless on my BBE and I went through massive gushers (wife wasn't too impressed). The BDB and practice fixed that.

To add one more data point here, the burrs on my Specialita touch pretty close to zero, and my typical espresso range is between 1.5 and 2.5 "steps" above that.

I made some measurements of the burr spacing a little while back using a caliper depth attachment and measuring through the hole in the top burr. It seems like the spacing changes by about 50 μm per "step" (1/6 of a turn). Figuring a burr outfall depth of about 100 μm, I reckon that puts my espresso range around 200 μm particle size, which is again pretty typical for espresso:



(Image is apparently from Chapter 13 in "The Craft and Science of Coffee", Brita Folmer.)

I would think a setting of 5 steps above zero would correspond with about 350 μm particle size, which is on the high end for espresso, but perhaps not impossible if someone is doing turbo shots?

Regarding burr alignment, I followed this video for the Specialita and had good results:

crwper wrote:To add one more data point here, the burrs on my Specialita touch pretty close to zero, and my typical espresso range is between 1.5 and 2.5 "steps" above that.

I made some measurements of the burr spacing a little while back using a caliper depth attachment and measuring through the hole in the top burr. It seems like the spacing changes by about 50 μm per "step" (1/6 of a turn). Figuring a burr outfall depth of about 100 μm, I reckon that puts my espresso range around 200 μm particle size, which is again pretty typical for espresso:
image

Thanks for sharing your data. Everything makes sense. With medium roasts, I'm usually at ~2.5 "step" which puts the particle size at 50*2.5 + 100 = 225 μm, pretty much in line with the chart. With light roasts, I'm at ~1.5 so that would be ~200 175 μm which is roughly where the espresso range starts in the chart.

crwper wrote:I made some measurements of the burr spacing a little while back using a caliper depth attachment and measuring through the hole in the top burr. It seems like the spacing changes by about 50 μm per "step" (1/6 of a turn). Figuring a burr outfall depth of about 100 μm, I reckon that puts my espresso range around 200 μm particle size, which is again pretty typical for espresso:

This is really useful information, thanks! In practice, I find that the Eureka dial has "reproducibility" up to about a 1/4 of a step (it's very difficult to make smaller adjustments, let alone see what one is doing). That would be 12.5 µm, which I believe is what the clicks on some of the 1Zpresso grinders correspond to, for example.

What I don't understand so well is how one goes from this information to median particle size, as reported in the diagram.

Awesome info @crwper thanks for sharing!

I had watched the very same calibration video (same guy that gave the +4-5 full steps for espresso in his review on the specialita). Finally decided to give it a try and it was worth the effort. My 0 is now clearly sitting at 4.5 and seems to have evened out the grind size a bit. Too late in the PM to go nuts with multiple shots (bye bye sleep) but my last shot came out ok if a bit quick (+1 step on the Eureka, 18.5g in, 18 sec PI, 22 sec Ext,45g out) taste was much more balanced than before shimming. Honestly I'm thinking placebo a bit here as it shouldn't have much of a perceptible impact but good nonetheless.

Great discussion!