Just finished a pound of stumptown guatemala la concepcion buenavista, which was good stuff.... yummy.

Having finished that, today I switched to another coffee... for the sake of discussion lets leave it unnamed for now, except to say it was roasted locally within the last 10 days and roasted a little darker than the stumptown.

New coffee: Started with 18g in a triple basket as a starting point, because that's what I was using with the stumptown. The grind was pretty clumpy compared to the stumptown. While pulling the shot, I got spritzers from the basket in my bottomless portafilter, which is very rare for me. 2oz shot in about 28 seconds. Crema was gold (I rely on crema color a lot to tune in coffees). Tasted pretty bad... sink shot. When I removed the PF, a big chunk of my puck was stuck to the bottom of the dispersion screen, even though the puck had plenty of headroom!

So another few shots... I tried downdosing to 17.5 and then 16.5g, while tightening up the grind 1.5 clicks, and doing a more aggressive wdt. 1.75oz shot in :30. Still issues with spritzing and coffee sticking to the screen.

This coffee goes in the trash!
Aside from being hard to work with, I don't see much potential with the flavor.
I think I am just spoiled, having had a few pounds of various stumptown coffees recently.

My question is really this: if your technique is consistent, and you can tune the grind to get the same volumetrics, what causes one coffee to be easy to work with, and another to clump/spritz/stick? I suspect it has something to do with "fines"?

If this can easily be explained with some search topics, feel free to just give me some keywords to search for... thanks!

I'm not an expert with roasting or blends at all.

But from my limited experience darker roasts have mostly been oilier beans, and have always made getting the grind adjustment difficult. I've usually struggled between gushers or machine stoppers, and rarely found the inbetween land that produced anything drinkable.

I also have not had a dark roast bean that smelled good to me - But the places I get coffee at don't roast dark... So most of these have been gifts, or random pickups that actually had dates on the package... Still, all have smelled burnt well before I did any prep to make a shot.

Well... these beans weren't a horribly dark roast, but they were darker than a northern italian roast, and they did taste burnt to me. Hence they are in the trash....might be something to your theory!

I've tried some coffees where my usually dosing, distributing, tamping routine wasn't up to the task of getting a good looking shot - I'd get all sorts of spritzers. I've tried distrubiting more thuroughly/carefully which works sometimes, but the most reliable "fix" is to just go down to a 14g double. It's much easier for me to avoide most channeling by using 14g for just about any coffee, and it's been my experience that these "tricky" coffees usually taste better at lower doses anyways. I don't know if that's because the channeling is causing so much overextraction as to ruin the cup at higher doses or if there's something about these "chanelling prone" coffees that works better at lower doses for taste as well. And then there are the beans that will spray like crazy for the whole shot and come out tasting delicious anyways, a good fix for those is to have a kitchen towel ready

My guess is it's the amount (or variablility) of fines that get created when grinding these coffees that makes them more difficult to work with, and also to pull better at lower doses. Of course any time I don't understand something about any beans, or espresso in general, I just blame it on the fines, they're very mysterious.

F.M. wrote: The grind was pretty clumpy... ...I got spritzers... ...Crema was gold... ...Tasted pretty bad... sink shot... ...big chunk of my puck was stuck to the bottom of the dispersion screen

It *sounds* like massive side-channeling and too fine a grind. Especially when I notice clumping, I reach for the WDT, and that usually helps. If you can control the channeling and get the pull to work out, the taste may follow suit.
OTOH, I have had coffees that I just couldn't tame, as well as those that I almost gave up on, and then got something wonderful for my troubles in the end.

I've had a blend of dark roasted arabicas once, dark, shiny, etc. I don't remember now how I adjusted the grind, but remember using low dose (13g) and low temp the lowest setting on Vivaldi - 88C - gave nice fruity-sweet, deep taste. At any higher temp it was undrinkable. The same was with higher dose - terrible.
I think I adjusted the grind to have a moderate flow, but I really do not remember, sorry.

It might be as simple as the coffee is no longer fresh. Some beans pull an acceptable shot at 10 days and some won't. Certainly a lot of what you describe is a hallmark of truly stale coffee. As an experiment, buy a bag of supermarket beans, the cheapest whatever that are clearly old. Aside from the taste, you will find that it's hard to find a good grind setting or achieve a consistent pour. It will want to channel more and often sticks to the shower screen too. As to clumping, that might be because it's a darker roast i.e. more oils.

The basic issue in grind changes and prep difficulties is bean brittleness.

If a bean is very brittle, it produces a lot more fines when ground than if it is soft. Since fines block the flow of espresso, brittle beans require a coarser grind (fewer fines) to maintain the same flow as softer beans. The coarser grind ensures that harder beans extract less for the same dose and flow rate, and therefore also taste harder (i.e. with fewer slowly extracting taste buffering compounds like caramels and melanoidins).

Very brittle beans could lead to channeling problems, if the coarse particles become so large they no longer are effective in locking the fines into place. However, I have no evidence of this.

In any case, your pucks sticking to the screen shows the problem is the other way around -- the beans are soft and producing few fines. You needed to grind finer, the puck became more water logged, mushier, and stickier, and so stuck to the shower screen. (By the way, this is neither a problem nor a symptom of anything bad)

If the blend included very soft beans like Sumatras or Monsooned Malabar, the grind needs to be very fine indeed, or the dose very high indeed, to produce enough fines to stop the shot from gushing at the end, or from channeling at the slightest hint of bad technique.

Bottom line, you should have dosed higher and ground finer. No guarantees about the taste; but the flow would have improved and you would have been able to come to a fair judgment rather than one based on poorl technique.

Interesting. It's hard for me to imagine dosing up beyond 19g, especially when coffee is already sticking to the dispersion screen. Your explanation makes sense though, I can see how brittle beans could create channeling issues..... although with better coffee waiting to be used, not really interested in adjusting my technique to compensate.

Fresh bag of hairbender awaits....

F.M. wrote:Started with 18g in a triple basket ... I tried downdosing to 17.5 and then 16.5g...
It's hard for me to imagine dosing up beyond 19g...

You are using routine doses for 58mm double baskets. Can't imagine dosing over 19g? Many would consider a 58mm triple basket to be downdosed below 20g.

Given your use of a triple basket, Jim's suggestion to increase your dose is a very reasonable one.