I have never really understood the nomenclature for baskets, either. *Presumably they are measured dosed up to the ridge for ridged baskets and it may well be that they are dosed without rapping the basket to settle. *After all, the people who name the baskets probably arent baristi! *If you dose above the ridge, sure, you should get more into it. *With ridgeless baskets, theres no indicator and, so, I have no idea how their dose is measured ... presumably they are dosed to a certain fill level. *In the real world, though, people dont view some arbitrary line in the side of the basket as the upper limit of their dose. *The upper limit of the dose is set by how far the shower screen protrudes into the basket. *This is different for different machines. *I would guess that baskets are measured independently of shower screens, seeing as baskets seem to be manufactured and on-sold to espresso manufacturers. *The take-home message is simply this: dont worry about what the basket is called!Ive worked with 21g baskets I believe, well actually, playing around with a gram scale, dosing and leveling it off, I got around 22-24g, but that could just be the scale playing up. In any case, why are there so and so variations?
As for peoples preferences for different baskets, I suppose that there are two factors at play. *One, which I know fairly little about, is how much area is exposed by the perforations in the bottom. *I have used one or two baskets that simply let too much water through. *The other one is the concept of brew ratios. *These are explained very well here. *In a nutshell, if you change the ratio of ground coffee to liquid extracted, you change the flavour of the resultant extraction. *If you try and get the classic 60mL in 30 seconds from a double basket, you can do that with a classic 14 grams or with 28 grams in a triple basket. *The brewing ratio of the latter will be higher than the former. *This is where the 60mL/30 second classic description of an espresso falls apart - people might say that both are espressos, but they are clearly very different drinks. *In fact, I would argue that the first is an espresso and the second is a ristretto. *Part of the reason why people might like different baskets is simply due to taste preferences between espresso style extractions and ristretto style extractions. *This will vary a lot from person to person, but also from blend to blend. *If 18g works well, why doesnt every one use them?
You will probably need to adjust the grind between the three doses above. *If you use the same basket for all of the doses, the 14g dose will require a finer grind than the 21g dose because there is less coffee to offer resistance to the water.Im being a little intuitive when I think 14g baskets dont hold enough grind in them to obtain a shot with more flavour or crema then the bigger sized baskets. This could be totally wrong.
Another thought was, does the size of the basket effect the time of the extraction and blonding? For example, if I tamped the same pressure on a 14g, 18g and 21g respectively, would they all pull 60ml in the same amount of time and the only difference would be how quickly they finish extracting coffee from the puck and begin to blond?
It is probably easier to pull a shot that looks acceptable with a higher dose than a lower one. *First, the more coffee you have, the more pigment you have to extract into the liquid and, so, the longer the extraction will last before blonding. *Second, the more coffee you dose, the less significant dosing errors of the same magnitude are. *For example, lets say that youre capable of dosing to within a gram of your target dose. *If you dose 10g, that 1g variance is 10%. *If you dose 20g, that 1g variance is only 5%, so it is easier to maintain consistency.
The machine can also make a difference; for example, I really noticed that it was easier to make decent shots with a larger basket on the Rancilio Silvia that I owned, but the La Marzocco FB80 that I worked on was perfectly capable of delivering stunning results with low doses.
Again, Ill reiterate - the brew ratio that you use is your own personal preference. *Beginners are probably well advised to go for higher doses for ease of use, but that doesnt mean that lower doses are for some reason unacceptable. *In fact, I have tried a number of coffees that were ordinary at high doses, but stunning at lower doses.
Hope that helps,