I'm new to espresso making. I have seen on this site advice to the effect that you should set your grind such that it chokes the machine and then dial back from there, until you reach a 25 -30 second extraction. I have also seen advice that says keep the grind fixed and dose up or down to achieve the same 25-30 s extraction.
So, in essence, either keep the compaction constant and vary the granularity; or keep the granularity constant and vary the compaction.

Have I got this right? If so, then these two methods are not equivalent, or are they? Or is there a single point where they are equivalent, but thereafter diverge?

Your help is much appreciated.

PS I'm not asking out of academic interest, so much as getting the best I can out of my machine.

HB thanks for the reply. It seems that the article is using extraction time as the benchmark. Please think of this question as coming from ignorance rather than arrogance, but how do we know this is the correct way to proceed. OK you can say taste, and I'm all for that, but is the extraction time sacrosanct?

Another thought occurs - sorry if I'm boring you. But if you talk about coffee extraction being a result of water contacting a specific surface area of coffee in a given time, then there has to be a meeting point between coarse and fine grinds. For example the surface area of more coffee at a coarse grind can equal the surface area of less coffee at a finer grind. But do they taste the same?

You're right HB he does talk of changing the flow rate, but he also talks of keeping it the same, depending on circumstances. I'm beginning to realize you guys have been through this many times.

Hi Ian,

that Espresso 101 is an excellent summary by Jim.

Don't think about it too much, just try it with your Bacchi and get a sense of how all these different factors play together.

In the end, it's the taste and mouthfeel that counts, so I think you are right about not simply dialling back from stalling your machine: it's not about riding the machine to its limits, it's about getting what you enjoy most out of a given coffee.

Enjoy!

The problem is that when you are diagnosing extractions, there are too many variables to keep track of. You need to keep some constant to understand the effects of any changes that you might be making.

I actually disagree somewhat about not using a stopwatch. In one of the trainings I did the trainer actually recommended using a fixed time extraction, and that helped me a lot. The tricky part is picking a time that fits your setup.

Really, this could be the same thing as saying "just pull a shot based on blonding", but I find sometimes that can be confusing and can actually be incorrect. Especially if there is channeling and blonding comes too early, etc.

And even though there are a larger number of variables I would suggest that there is a much smaller set of results. So you actually don't need to go tweaking all combinations.

For me, I usually keep the time consistent and alter temp and/or dose. This has the effect of also keeping the grind consistent once you dial it in. The temp is usually adjusted fairly quickly and easily. So lastly you can then experiment on the dose (which will then cause you to re-adjust the grind).

Which is pretty much exactly what you find in the Espresso 101 sticky.