Please remember I grabbed the 5 grams as a nice round number, a start for our arguing.

Maybe first drops is the best preinfusion milestone, whereas the ca. 5 gram mark is an added marker useful only for flow profiled shots.

RapidCoffee wrote:The DE1 allows an unprecedented degree of insight into the extraction process. Here is an extraction inspired by Dan's 4-9-6 pressure profile in the Bianca review: preinfuse at 4ml/s to 4bar, briefly increase pressure to 9bar, then gradually decline to 6bar until target weight (32g) is reached.

The 4-9-6 was 4bar for the initial phase rather than 4ml/s @ 0 bar. With levers you can hit your desired initial pressure within 1-2 seconds.

I believe this highlights a common misconception. It makes more sense to describe preinfusion in terms of input water flow rate rather than pressure. Unfortunately this is not possible on most machines today.

And yes, I can preinfuse the puck faster on my rotary pump Spaziale, because the water debit (flow rate, not pressure) is much higher. Presumably you can do the same on your levers.

I'm starting to record both the time at 5g out, and the time (roughly) when the drips change to a steady flow. I am not yet consistent at remembering to record them yet, so it may be a bit before I have enough data points.

RapidCoffee wrote:I believe this highlights a common misconception. It makes more sense to describe preinfusion in terms of input water flow rate rather than pressure. Unfortunately this is not possible on most machines today.

I don't think Dan had any misconception with his recipe. Maybe you just read it wrong? I'd bet the DE1 can do it correctly.

Most machines probably operate based upon pressure because it is a lot easier to measure pressure than flow rate. I really like having both and I use both, but I prefer to use pressure early and flow later. It sounds like the DE1 distorts flow rate though, with all of the extra head space. I find the mass flow rate from a scale to be more useful than water volume rate into the group anyhow. The former tells you what is happening with your coffee and the latter isn't meaningful until you've filled up your group head with water. Unfortunately the two are confounded when you're measuring inlet flow.

So why do you think it is better to describe preinfusion by flow rate?

Tonefish wrote:So why do you think it is better to describe preinfusion by flow rate?

I'm sure John will have a good answer, but mine is that the pressure at the puck is zero during preinfusion, and will remain zero until the basket is full of water.

Although my modified GS/3 AV displays the flow rate pretty accurately, I don't see any need for it when using long, slow preinfusion for a Slayer-like shot, which is the only type of shot where, IMHO, it makes sense to talk about preinfusion.

I continue to believe that the first signs of drops and/or the first sign of a rise in pressure are sufficient to determine preinfusion time.

I was triggered by the comment that if it still drips at 5 g you're not making espresso anymore, frightened as I was I did a quick measurement.
With my current settings (knew it to be a very fine grind) it took a minute to reach 5 grams and only at around 9-10 g out the flow became a steady trickle. Result shown below, a nice ristretto 14.5-15g in and 24 out (forgot to capture shot time but that was probably 45 second after PI).

I'm thinking that when comparing PI across machines you'll have to account for 'dead space' (if only for different filter basket sizes and fill volumes) which will be different for each type of machine so using a milestone like f.e. the time to reach 5 g would seem to work well to be able to compare.
Arriving at a ratio of some sort might also work, I have no clue what that would be though as there is no PI volume we can measure...total shot time over PI time might work but that would likely have to be normalized to a standard output volume...food for the scientists here.

Tonefish wrote:I don't think Dan had any misconception with his recipe. Maybe you just read it wrong? I'd bet the DE1 can do it correctly.

You'd lose that bet. Take another look at the graph I posted. The DE1 cannot ramp up pressure instantaneously (nor can any machine).

Tonefish wrote:So why do you think it is better to describe preinfusion by flow rate?

Again: look at the graph. During preinfusion, pressure tells you nothing, and flow tells you everything. Pressure only rises when the puck saturates enough to provide resistance to flow.

RapidCoffee wrote:You'd lose that bet. Take another look at the graph I posted. The DE1 cannot ramp up pressure instantaneously (nor can any machine).

Maybe just another limitation of the DE1. My Ulka pump driven E61 machine can hit 4 bar within a second. Here's the data: E61 Group Pressure Correlation to Brew Pressure. Most people don't have this kind of data which can lead to misconceptions about the performance of these machines. Maybe you are right about the DE1 though, maybe it can't do it. It looked to me like you were controlling flow rather than pressure as Dan had prescribed. If you actually programmed what Dan said, I'm sure you'd have a better and more comparative result. Heck, I'd like to see how quickly the DE1 can get to 4 bar too.

Again: look at the graph. During preinfusion, pressure tells you nothing, and flow tells you everything. Pressure only rises when the puck saturates enough to provide resistance to flow.

See the data above, and again, flow to fill the group head has no value. Even at the group, with reasonable head space the pressure increases within 2 seconds in a conventional E61. If flow is telling you what is happening in the coffee that is great, but in your case a lot of it isn't. It took you about 13 seconds to hit 2 bar, but again, I think that is incorrect programming of your stated objective to replicate Dan's 4-9-6, versus a DE1 limitation (or at least I'd hope so). I think your machine can get closer, you just have to program it correctly.

Even though you've taken this a lot further, do you recall that my only comment was that you did not do what Dan had prescribed and that other (probably most) machines can get up to pressure much quicker? I'm pretty sure that is factual and no need to carry this on unless it serves this Simple Measure of Preinfusion topic. It will never be simple to use inlet flow for this measure when head space varies so much and most machines do not offer inlet flowrate information.

I am still at a loss to understand why first drops or 5 grams matters on the same machine BECAUSE aren't there so many other variables that come into play that impact the time even with the same coffee? Can someone explain this is a non-engineer type?