JohnB. wrote:I'm also aware that once those areas get filled after a thorough burrs out cleaning the grounds stay put & don't come flying out each time you run the grinder.

What makes you so confident in this statement?
You feel that there is no contamination? Based on what?

Finding out how the grinds packed in the chamber interact with those going through is a non-trivial experiment; one that, to my knowledge has not been done. Until it is, the basic age distribution of the grinds in your PF is unknown; as is the effectiveness of the various means of keeping the grinds fresh.

One advantage of cheap home grinders, like the basic Baratza or Capresso Infinity, is that the burrs can be removed entirely, and the grinder knocked out, in about 30 seconds. Fresh grinds are guaranteed. The M3 and Vario only hold around 3 grams total in the grinder, so sacrificial grinding more or less guarantee that probably all but one gram is fresh. A commercial grinder holds 10 to 30 grams compacted in the chamber. How much of that is exchanged at each grind, 1%, 5%, 10% ? Nobody knows.

But at the cost of going on like a broken record: even at 10%, it really isn't such a big deal. Take a coffee, grind a few grams, put it away for a day. Then brew two cups of coffee fresh ground, and one with 20 percent of the day old ground. Pick out the odd cup. For most people, 20% to 25% will be the low limit of being reliable on this exercise. Moreover, I have yet to get "thin and bitter" doing this exercise even if I use 100% day old coffee. "Thin and bitter" is just not something properly brewed day old ground coffee does. That is why it is possible to sell tens of millions of pounds of preground coffee each year. Now if the people all worried about this had described their purportedly stale shots as "unaromatic and bland," I might be laughing a little less hard.

another_jim wrote:Now if the people all worried about this had described their purportedly stale shots as "unaromatic and bland," I might be laughing a little less hard.

Mock me if you like. I've freely admitted that I'm not very good at describing flavors. Semantically, Bland does not seem all that far removed from Thin. The shot wasn't bitter like Lavazza at a Shell Station bitter, just relatively bitter compared to the 2nd and 3rd. Or perhaps by Bland you mean Unemotional

Thanks for the validation that perhaps 20% old grounds is the detectable threshold in the cup. The extra grounds I've measured are around 1~2g in a timed 1s pulse. In a 8.5g single, that's hitting the 20~25% range.

another_jim wrote:But at the cost of going on like a broken record: even at 10%, it really isn't such a big deal... Moreover, I have yet to get "thin and bitter" doing this exercise even if I use 100% day old coffee. "Thin and bitter" is just not something properly brewed day old ground coffee does.

I agree that 10% stale grinds is not of great significance. But 100%? For espresso? Whenever I've tried using day old grinds for espresso, I get pours that look like this - and taste the way they look.

RapidCoffee wrote:I agree that 10% stale grinds is not of great significance. But 100%? For espresso?

Yes, Abe and Jim's report Experiments with Preground Coffee for Espresso makes that claim. Barry Jarrett and others have suggested that ultra-fresh coffee is less unruly if ground and allowed to degas for 15-30 minutes. I haven't tried it, but it makes sense.

Yes, I read (and responded on) that thread. However, espresso differs from non-espresso brewing, and 15 minutes is significantly less time than a day. It's likely that the type of coffee beans, and degree/age of roast, also have an impact.

I try to keep an open mind. But for now, I'm sticking with freshly ground coffee for espresso.

I apologize for my tone here and in some my recent posts. When things get confused, I get mad.

The confusion here is that we are not distinguishing two kinds of bad shots: sink shots and "why bother" shots. For instance, a properly pulled shot made from completely stale coffee is like a lot of espresso in Italy, by no means a sink shot, but instead a "why bother" shot -- fine at a pinch, but not what we signed on for when we made espresso our hobby.

My belief is that not making this distinction is becoming a real hurdle on HB when newbies and experienced members are exchanging views. Newbies, on the whole, would be happy to make consistent "why bother" shots like they got in Italy; and they are looking for the skills, grinders, and machines that will give them this instead of sink shots they are plagued with when starting out. Skilled home baristas rarely pull sink shots. Instead they want to get beyond "why bother" shots, and are hoping to achieve exciting tasting and distinctly pleasurable shots every time they walk up to their machine.

Newbies can achieve their goal by getting a naked PF and learning how to be consistent. They may need a second generation of machine and grinder if they bought blind, but the entry level equipment we recommend is fine if their goal is no sink shots and good consistent "espresso Italiano" quality. I've been getting annoyed, on occasion, because a lot of the advice to newbies has been well beyond this basic step.

For the people looking for consistently pleasurable shots; getting great coffees and blends is the first step. Then revising ones technique and getting the right equipment to do those great coffees justice are steps two through a fairly large N.

Purging the grinder is certainly one of the extra steps to consistently great shots. But it's just one refinement among many. If people go further and do a full court OCD press on a few of these details, their shots will not improve. If they make all these efforts using mediocre coffees, their shots will not improve. I will continue pointing this out; improved espresso comes from great coffee and making the appropriate small refinements to every prep detail, not in over the top precision to just a few.

On the other hand, when a newbie finds espresso happiness with fully staled Lavazza Rosso with 30% Robusta, I guess we still need to tell them that despite the marvelously consistent shots, it's probably not the way to go in the long run.

Bravo

another_jim wrote:I apologize for my tone here and in some my recent posts. When things get confused, I get mad.

At the same time, the question (as I understand it) is: Can you make a shot that isn't compromised without sacrificing two or three grams before every individually ground dose?

Whether it is compromised to the point that it is a 'why bother' or a 'sink' shot is somewhat immaterial (well, not really, just as it pertains to this question) and possibly a result of some hyperbole.
My answer has been, along with many others, that it is possible to clean out a grinder so that you're using all fresh ground coffee (within measurable parameters outside a laboratory) for every shot.

My guess is on a commercial grinder, if you empty the hopper, then pulse the grinder until you can no longer sweep out any grinds, you will still get around .75 to 1.5 grams of past grinds in each shot. I base this on the variance I get shot to shot feeding in say 15 grams and getting X grams out. FWIW, I sacrifice grind in the morning, but not during the day. I doubt this makes, but I'm a fan of imperfect but reasonable compromises.