I never bothered with this technique becasue it always felt unpredictable, but maybe it's time to learn more about it so that I can harness it as a tool in the arsenal. A few questions:

- Do you use the pre-wetting feature of your E61 grouphead? If not, why?
- If you do use it, do you limit it to specific types of beans / roasts?
- Is there any significance in how close the lever is to the microswitch that turns on the pump? Should it be just enough for the pressure gauge to show that the valve opened, or as much as possible before it actually presses the microswitch?
- How long do you hold the lever in this position before lifting it all the way to start extraction?
- Also, is your machine plumbed-in or one with a water tank?

Thanks!

I don't pre-wet, but to my understanding it's only useful if you have your machine plumbed in and some water line pressure (which is usually around 2 bar here).

With a vibe pump/reservoir, there's no real pressure, so keeping the lever in the pre-pump activation position will only release a few drops and cause the brew head to heat up quickly. That's not really desireable I believe.

I actually tested it with my non-pumbed-in machine, and 30 sec of pre-wetting increased the weight of the puck by 6 gram (after lowering the lever all the way to drain water). I think that's not negligible, especially not for the single shot basket that I use, which holds 11.5 gram.

My boiler temperature is set to 95c.

That's far too slow to be useful. You're looking to add 2 to 2.5 times the weight of the grounds in water in the fastest time possible under lower pressure. If you add too little water too slowly then the puck is getting wet unevenly for a gradient of time.

The answer is a flow control where you can direct 3-4ml/sec of water to the puck at very low pressures (1-2bar),wait for the puck to saturate and the pressure to rise to 4bar signaling the end of pre-infusion and then go up to your full flow rate and peak pressure, whatever those may be.

If you have a plumbed machine with 1 or 2 bar of line pressure you can do something similar.

PIXIllate wrote:That's far too slow to be useful. You're looking to add 2 to 2.5 times the weight of the grounds in water in the fastest time possible under lower pressure. If you add too little water too slowly then the puck is getting wet unevenly for a gradient of time.

If when high-pressure extraction only starts after the puck is fully wet (when I pull lever all the way), does it really matter how long wetting puck took? Something that's already wet can't get wetter, no?

The answer is a flow control where you can direct 3-4ml/sec of water to the puck at very low pressures (1-2bar),wait for the puck to saturate and the pressure to rise to 4bar signaling the end of pre-infusion and then go up to your full flow rate and peak pressure, whatever those may be.

The problem with a flow control device is that I'd have to give up the grouphead thermometer to install the grouphead pressure gauge. That's why although I bought one, I haven't installed it yet. I'm still experimenting with the grouphead thermometer. If a long pre-wetting can replace the long pre-infusion stage that many people recommend for light roasts, I might not even need the flow control device.

If you have a plumbed machine with 1 or 2 bar of line pressure you can do something similar.

If I'm calculating correctly, on an E61 machine like mine, setting the PID to 95c means the boiler is at 107c (given a default offset of 12c). This translates to 1.3 bar which is within the range you mentioned. In my case, the offset is actually 16.5c (you can read the full story here), so pre-wetting pressure may be even higher, around 1.5 bar.

Not sure if losing the temperature sensor is worth it over installing the flow control kit and pressure gauge. What you gain in pressure profiling, you lose in temperature reading.

I'm facing a similar issue with my PID controlled HX. Temperature is usually stable, but sometimes it isn't. Especially if you do multiple shots in a row, the temperature sensor is invaluable (altough, if it's cappuccino's I'm making, I don't really care for taste that much).

Having your machine plummed in and use the line pressure is somewhat of a middle ground where you can do pre-infusion, without losing the pressure sensor. For a vibe pump they say it doesn't really add much to have flow control, since the puck is hit with lesser pressure in the first place, and a vibe pump ramps up pressure more than a rotary pump which is almost instant.

I'm interested in what more knowledagble people have to say about this. Would like to try out new toys as well, but so far I don't see the benefit yet.

I found E61 middle position with a reservoir machine to be less than useless. It made repeatability worse. Uneven wetting across the puck led to channeling. Also consider that extraction begins as soon as water contacts the grinds (like an immersion brew). Uneven wetting, even just over time, would then lead to uneven extraction.

On the second question, I'll take the thermometer over flow control in an E61 HX. Temperature repeatability and control is important for all coffees. On a SB/DB with a PID you're probably within +/- 1C, which is unlikely to get you a big gain in the cup to control much better. There, I think you have potential to get more-easily tasted changes with flow control.

You can pre-wet/pre-infuse an unplumbed e61 w/o an FCD easily, regardless of the type of pump. Simply raise the lever to full on for a few seconds, then move it to the middle position and wait. You can usually have the pump on for up to about 5-seconds without building significant pressure. One could temporarily install a pressure gauge to judge for any particular machine how long to raise the lever, or just mess around and see what happens Whether one should or needs to pre-wet/pre-infuse, it's up to you to judge whether this is useful...it's your coffee! FWIW, I used to do this all the time on my HX, and also with my DB before I installed the FCD kit.

I tried the middle position and also turning on until 4 bars and back to middle and found it inconsistent. On some shots it prewets too much (even though I used the same timing) and I ruined the shot by the flow being too great. At the price of coffee, I finally went back to just the straight pull. One suggestion was to spritz the PF first to wet the top.. I tried that too but didn't notice much difference.. although I didn't do it enough to really test it well. Drops in my HX don't come out until about 8-11 seconds so I think the pre-wetting there is doing its job mostly.I also agree about the thermometer on an HX.. I'd never replace that with a pressure meter as, in an HX, temperature management is only possible if you have some reading near the group. Pressure profiling is just so much easier with a lever and a pressure gauge. If the manufacturers would attach their existing pressure gauge to the group, you wouldn't need to choose and this gauge would be waaaaayyyy more useful than it is now. Doesn't seem like a big change.

Jeff wrote:I found E61 middle position with a reservoir machine to be less than useless. It made repeatability worse. Uneven wetting across the puck led to channeling.

Isn't this expected if the puck is not fully wet? This would probably apply if pre-wetting is only done for a few seconds. But what about doing it for 30 sec? Do you remember for how long did you pre-wet the puck?

On a SB/DB with a PID you're probably within +/- 1C, which is unlikely to get you a big gain in the cup to control much better. There, I think you have potential to get more-easily tasted changes with flow control.

I would be extremely happy if I could get anywhere close to +/- 1C with my SB E61 machine with PID. I can't even get to +/- 2C when measured at the puck. The situation is not as bad at the grouphead.