oton wrote:What's the size of the "non true" double?

Rather than getting bogged down in volume discussions, seee Brewing ratios for espresso beverages. Generally speaking, espressos pulled with a higher brew ratios (ristrettos) have a larger margin of error than those with lower brew ratios (doubles).

I never ever bother to shoot for a certain volume of liquid. As a guideline I watch the pour. If obviously too fast/slow, I adjust accordinglly. If in the ballpark, I further rely on taste alone. This means that depending on the coffee used, the pour will either drip at first and then slowly develop in a stream, or start off a bit faster. This means I end up with anywhere between 30ml and 60 ml of coffee beverage in the cup. Volume alone tells me nothing.

malachi wrote: 4 - get a good consistent bed of coffee in the portafilter basket without gaps either in the bed or between the bed and the portafilter wall (don't tap or rap the edge of the portafilter is a good short cut).

Sorry to pull up an old and somewhat contentious thread but I'd seen part of this mentioned in another thread during my research to figure out why I'm struggling to get decent shots like I was up until a couple of weeks ago. I've had no change in beans or equipment, and I thought I had no change in technique.

This is the part I've seen mentioned elsewhere "don't tap or rap the edge of the portafilter" and I haven't yet found an explanation for it. I've stopped doing it but I was wondering what the negative effect of doing so is?

Also, I could use some clarification on "without gaps ... between the bed and the portafilter wall". I understand getting a good bed of coffee in the basket but what do you mean by between the bed and the portafilter wall?

Thanks.

Once tamped, the coffee grounds form a puck/bed/cake inside the basket, ideally making full contact along the basket interior vertical wall. Assuming proper prep, the puck would present a consistent surface across the top with no gaps or spaces between the puck and portafilter. Think of putting a quarter into the basket. The gap would be between the ridges of the quarter and the basket interior wall.

Tapping, rapping, or otherwise physically jarring the prepared puck may disturb this consistent contact, creating a space between the outer circumference of the coffee puck (the quarter's ridges) and the vertical wall of the basket.

The potential negative effect of creating a gap or space is that it provides a path of less resistance for the incoming water, producing a faster flow through the gap. The inconsistent flow throughout the puck would result in less even extraction across the puck, commonly known as channeling. If you have a bottomless PF, you might see spritzes or certain areas on the bottom that look significantly lighter. The resulting cup will taste, well, uneven. Channeling will produce overextraction (at the gaps) and underextraction (everywhere else). This is one case where two great tastes don't taste great together.

the_trystero wrote:This is the part I've seen mentioned elsewhere "don't tap or rap the edge of the portafilter" and I haven't yet found an explanation for it. I've stopped doing it but I was wondering what the negative effect of doing so is?

At best it serves no purpose, since the incoming, high-pressure water will wash the loose grounds off the side of the basket. At worst it may separate the compressed puck from some portion of the basket wall or create a fissure, allowing water to channel through.

Thanks for the detailed explanations.

On this part I assume that Chris just meant "between the bed and the portafilter basket wall"? "without gaps ... between the bed and the portafilter wall"