I have a machine with full flow profiling capability through a needle valve that I can adjust on the fly, (like a Bianca). AND I have a pump interrupt switch for it so I can fill up the head space and then turn off the pump to let it soak, while the solenoid remains energized. So both options available to me whenever I want.

Say, if I fill the headspace and bloom for 30s before turning on the pump, versus if I pre infuse at super low debit for 30s before first drops, then open the needle and speed up the flow for the main extraction?

What I'm looking for is advice on the taste effects of one versus the other in the espresso. Which might you do in which situations?

-Peter

Wouldn't this generally follow the rules for espresso where pressure is relation to heat and grind is related to flow? I have no idea as I do not do espresso. What have you seen so far in your trials?

Seems to me that they'd be similar since the water penetrates the compressed puck only so fast under super low pressure anyway.

Have you tried both?

I honestly don't know, but I am following this thread in the hopes of hearing from someone who does!

Tonefish wrote:Seems to me that they'd be similar since the water penetrates the compressed puck only so fast under super low pressure anyway.

Have you tried both?

I have tried both. Been doing it for months now. And some coffees do better one way versus the other. But I don't know why. (I know this capability is still kind of new and not available to a wide audience yet). So I was looking for a generalization: "Soak and bloom tends to produce these effects, and long low flow pre infusion tends to produce those effects.

Anyway, as physical processes, there is a difference. Even at super low flow like 1.5'ish ml/s, pressure will still start building when all the spaces are filled. You can see this in a video of a Slayer shot. This is not the case when you stop the pump for a bloom. When I soak and bloom, pressure barely goes above zero until I turn the pump back on for the extraction.

For reference, our own Shadowfax's Slayer shot. You will see that even during low flow pre infusion, pressure eventually rises to near full extraction pressure before he hits it with full flow. I do the same thing when I'm not shutting off the pump entirely for a soak and bloom: -Peter

I'm not sure how much soak you actually get in a soak and bloom. If you hit a fine ground puck with 9 bar and high flow for a few seconds, there is very little soak. So if you cut the pump, and there isn't much water in the head space, there won't be much soak. This doesn't mean it won't taste better; but it does mean that what tastes better is a long wait with a damp versus wet puck.

The puck is supposed to be fully infused with water for the bloom, not just the headspace.

Yes, this. I did a cocktail napkin calculation of how much extra water you need once the headspace fills, based on the PI flow rate of about 1.3 ml/s. It's all pretty inexact, though. Definitely not lab grade work, here.

-Peter

another_jim wrote:I'm not sure how much soak you actually get in a soak and bloom. If you hit a fine ground puck with 9 bar and high flow for a few seconds, there is very little soak. So if you cut the pump, and there isn't much water in the head space, there won't be much soak. This doesn't mean it won't taste better; but it does mean that what tastes better is a long wait with a damp versus wet puck.

I've pulled and cut a couple pucks recently with what I understood to be a soak and bloom. What provided the best flavor outcome for me (with the Bianca) is to set the paddle to the middle position and cut the flow off when it reaches 4 bar. This is normally 15 seconds or so. The soak continues for 30 seconds, and my preferred grind lets out a single drip or less during this time. If I shut the machine off, pull the puck, and cut it in half at that point it is well saturated. If I continue the shot, I'll run for 35-45 seconds post pre-infusion for very light roast or 25-35 for light. The final pucks are pretty soupy and appear uniformly soaked.

Running as quickly up to 9 bar as the Bianca allows and cutting flow didn't provide the same well soaked puck. It was wet on top, damp in the middle, and unevenly damp at the bottom. The flavor also suffered at my skill level; I couldn't work with as fine a grind to hit my time and volume targets. It's possible that a better recipe would provide better flavor with this soak and bloom method.

That's been my experience too. I might be that the effect on the puck of these various techniques depends on the specific machine and basket. I'm with you, I like to make sure the puck is completely soaked (I wait til I see a drop or two) before cutting the pressure and waiting.