I looked through my photo archives and found this shot that I did at Revolver in Vancouver, CA, with grounds from a Mythos, about a month ago.

The point I want to make with this shot is that the cooling effect of the grounds is only 2°C, and because of this the DE1+ is able to hit +/- 0.5°C accuracy through the entire post-preinfusion (ie brew) part of the shot.

Other things to note is the less significant (but still there) little wobble at the start of pressure buildup, puck erosion visible as flow rate increases, and 1.5 bar overshoot for a few seconds at pressure ramp up, from the DE1+ needing some PID tuning. There's also a 9 bar-to-6 bar pressure profile programmed in there. The "noise" on the pressure sensor is also less than with other grinders, which makes me think it's the Mythos' grind quality at play.

Just got a PM from Sam, who in talking to George, was trying to understand what he was trying to get at with the 1 bar question.

Turns out George is interested in a slow preinfusion approach, which makes a lot of sense.

I also think I understand why George and I are not managing to communicate, and it's because we're talking about two very different measurements with the same word.

Let me explain...

Virtually every espresso machine out there (except notably the Strada EP), when you ask for X bar, is measuring it at the pump, behind a flow constrictor that is calibrated somewhere around ~4 ml/second to ~5 ml/second.

So, if you ask for "3 bar" out of those machines during preinfusion, you're getting some sort of flow rate that happens to give that pressure when the pump presses against the flow constrictor. Backpressure is automatically created in those machines

The Decent Espresso macines don't measure pressure in this way. The DE1+ measures pressure on the puck itself, and so during preinfusion, we're at zero bar for most of it, because the puck is absorbing all the water. At a 4ml/second flow rate, a traditional machine might tell you it was at 3.5 bar, but we'd report that as zero bar until the puck itself started resisting taking on water.

This is a really fundamental difference between "measure at the pump" vs "measure at the puck" pressure monitoring, and it makes it very difficult to compare what the DE1+ is doing to a "measure at the pump" machine.

I've devised a new experiment, which I'll expain in the next post, which might be more in the direction George was meaning to go in.

Even though the DE1+ will do it, I haven't yet made the time to try a "very long and slow preinfusion" shot, and I thought I'd try one.

I set the preinfusion speed to 0.22ml/s, with a timeout of 60s. I didn't know if that would be enough time. Interestingly, in the charts you can see the beginnings of a pressure rise at around 50s, so I think a slightly faster rate (maybe 0.3ml/s) might be enough, and that would correlate well with the 1:1 grounds:water ration I've seen (ie 0.3ml/s x 60s= 18g of water, into a 17g dose of beans) to saturate a puck.

What surprised me is that the shot tasted GOOD. Low acidity, much more aggressive than a short-preinfusion shot, and definitely more like drip coffee with stronger mid-to-low notes than this bean usually gives me.

I tasted the shot both straight and with milk, and both styles were definitely defensible as excellent and interesting shots. It pulled, after preinfusion, in 22s to a roughly 2:1 ratio (17g in, 31.7g out).

So, I do think I need to experiment more with this style.

Temperature wise, the DE1+ was putting near boiling water in, in a desperate and futile attempt to raise the puck temperature (the bean:water ratio being so skewed as to make that impossible). Next time, I will turn temperature profiling off, and use a stable water temperature.

decent_espresso wrote:Just got a PM from Sam, who in talking to George, was trying to understand what he was trying to get at with the 1 bar question.

Turns out George is interested in a slow preinfusion approach, which makes a lot of sense.

John, your explanation makes perfect sense. but I was talking about puck pressure all along.

This is a typical profile I am(and I think George? not too sure) talking about.



from http://www.portaspresso.com/page0051.html

This is how the system is setup and the gauge position so I'm really talking about above puck pressure.



Pardon the kindergarten drawing.

decent_espresso wrote: The Decent Espresso macines don't measure pressure in this way. The DE1+ measures pressure on the puck itself, and so during preinfusion, we're at zero bar for most of it, because the puck is absorbing all the water. At a 4ml/second flow rate, a traditional machine might tell you it was at 3.5 bar, but we'd report that as zero bar until the puck itself started resisting taking on water.

This is a really fundamental difference between "measure at the pump" vs "measure at the puck" pressure monitoring, and it makes it very difficult to compare what the DE1+ is doing to a "measure at the pump" machine.

The fact that you are measuring and displaying actual pressure and flow during the shot are giving visibility to what had previously been hidden or obscured. The fact that pressure/flow are a little messy or don't match expectations aren't always due to problems. Frequently it is only when newly controlled systems bring visibility to previously obscured processes that people learn what is (or has always been) going on.

The initial phase of water hitting the tamped espresso brings together fluid dynamics, thermodynamics, particulate pseudo-solids (my word because I don't know the proper term), and coffee chemistry. The fact that there are so many variations to this part of the espresso ritual shows the complexity.

The combination of control points, sensors, and visibility that your machine brings to espresso coupled with the open-source flexibility to leveraging the machine's components is pretty thrilling to see. I suspect that it will fuel some real breakthroughs.

samuellaw178 wrote:John, your explanation makes perfect sense. but I was talking about puck pressure all along. This is a typical profile I am(and I think George? not too sure) talking about.

Ok, cool, that's a graph I can sort of understand.

I say "sort of" because *something* is happening in the first 14 seconds, but what that is, is not displayed there. My guess is that water at some sort of flow rate is entering the system, and because they're not measuring flow rate, and they're measuring pressure at the puck, the chart doesn't tell us what is occurring.

If you happen to know what flow rate is being introduced into the puck in those first 14 seconds, that would be very instructive. I see no mention of flow rate in the link you mention, but perhaps I just didn't see it.

Now looking at the text for clarification... and ...

This sentence, from this article, makes no sense to me:
"Pre-infusion: Pressure is ramped up to approximately 0.5 bar at which time a pause is held. "

If the puck is absorbing all water, which it would do at the beginning of a slow preinfusion, how could there be any pressure at all?

If the water were introduced REALLY FAST you might have a temporary blip of 0.5bar before the puck manages to absorb the water. However, this tells us nothing about how much water was introduced into the puck, which is kind of an important piece of information.

If pressure is ramped up to 0.5 bar fairly slowly (say, at 1ml/s for 10s ) then a 15g puck would likely be fully saturated at that point.

Now THAT would be interesting to me, because then the 0.5 bar number looks very much like the "exit preinfusion at xx bar" feature in the DE1+, and in my experience, ~0.7 bar is a good trigger to detect full puck saturation, and then that article and my experience are in close agreement. What we'd need to add to the DE1+'s shot profile is a pause, as described in the link.

I don't really understand the idea behind holding pressure at 0.5 bar, unless the puck is still getting saturated, because otherwise you'd be slowly dripping water out the bottom. If water is not coming out the bottom, then the flow rate is half of what I said above, more like 0.5 ml/s, and preinfusion is ending much later.

decent_espresso wrote: I say "sort of" because *something* is happening in the first 14 seconds, but what that is, is not displayed there. My guess is that water at some sort of flow rate is entering the system, and because they're not measuring flow rate, and they're measuring pressure at the puck, the chart doesn't tell us what is occurring.

If you happen to know what flow rate is being introduced into the puck in those first 14 seconds, that would be very instructive. I see no mention of flow rate in the link you mention, but perhaps I just didn't see it.

To me the drawing looks like a Portapresso, so I would assume that 0 marks the time that the device is "flipped" and relatively flow rate is very high to instant.

decent_espresso wrote: Now looking at the text for clarification... and ...

This sentence, from this article, makes no sense to me:
"Pre-infusion: Pressure is ramped up to approximately 0.5 bar at which time a pause is held. "

If the puck is absorbing all water, which it would do at the beginning of a slow preinfusion, how could there be any pressure at all?

If the water were introduced REALLY FAST you might have a temporary blip of 0.5bar before the puck manages to absorb the water. However, this tells us nothing about how much water was introduced into the puck, which is kind of an important piece of information.

If pressure is ramped up to 0.5 bar fairly slowly (say, at 1ml/s for 10s ) then a 15g puck would likely be fully saturated at that point.

Now THAT would be interesting to me, because then the 0.5 bar number looks very much like the "exit preinfusion at xx bar" feature in the DE1+, and in my experience, ~0.7 bar is a good trigger to detect full puck saturation, and then that article and my experience are in close agreement. What we'd need to add to the DE1+'s shot profile is a pause, as described in the link.

I don't really understand the idea behind holding pressure at 0.5 bar, unless the puck is still getting saturated, because otherwise you'd be slowly dripping water out the bottom. If water is not coming out the bottom, then the flow rate is half of what I said above, more like 0.5 ml/s, and preinfusion is ending much later.

It could just be a difference in terminology, I believe Slayer started talking about "pre-brew" instead of "pre-infusion", but what it is may not really matter. In that graph, you could assume the flow rate is VERY high around 0s, then goes to essentially zero once 0.5 bar is reached. This is certainly possible without any drips occurring, you just need to grind finer, then when you think you ground fine enough....go finer! Try it on a light roast, you'll be surprised if you haven't before. What was a choked shot before you'll be surprised to see flow will come pretty easily with this 30s or so "soak".

I can tell you this high initial flow, but no/low pressure "soak" phase, is very key to getting extreme light roasts to work better as espresso. Other things can be done with temp, grind and microwaving beans, but I've found the long "soak" works best for me. And I'm guessing this is what others are trying to determine if your hardware is capable of achieving. To me it looks more than capable, and if anything is a matter of PID loop over-riding or tuning during different phases, or even just plugging in the desired numbers.

But I would say that some are coming from fully manual machines, or lever machines and trying to translate their experience there with how it would fit on your machine.

decent_espresso wrote:Ok, cool, that's a graph I can sort of understand.

I say "sort of" because *something* is happening in the first 14 seconds, but what that is, is not displayed there. My guess is that water at some sort of flow rate is entering the system, and because they're not measuring flow rate, and they're measuring pressure at the puck, the chart doesn't tell us what is occurring.

If you happen to know what flow rate is being introduced into the puck in those first 14 seconds, that would be very instructive. I see no mention of flow rate in the link you mention, but perhaps I just didn't see it.

John, the reason I brought that up was not because I am trying to say it is better than your device and what not. That is because that is the closest example I have and nothing seems to articulate more clearly with an actual example.

You can look at the video if not already. All the water is sitting on the puck at atmostpheric pressure (all at once at t=0s), so very high instant flow rate but no pressure(at least below the detection limit). Then the piston is gradually lowered to generate pressure. Flow/compression rate is unknown/unmeasured and I too agree it is important.
http://www.youtube.com/watch?v=hhpQFlwgS5k

Yes, during the 14 second, there is no pressure registered, but certainly there are water flowing into the puck (before 14s). That part is clear. By how much, I don't know. You can theoretically calculate that, based on the piston travel and diameter. That is why flow profiling makes more sense in the preinfusion phase, and I think your Decent could do more than just pressure or flow profiling alone.

In pressure profiling, what really matters is the pressure ramp up rate from 0 bar (also can be measured via water flow/saturation rate into coffee puck). Whether you have 10mL hot water sitting above puck, or 2L hot water sitting above puck, the puck couldn't care less. It is the rate of water flowing into and through the puck that matters. If you measure pressure, it will be registered as pressure ramp up ; if you measure flow, it will be a function of pump flow rate (in Slayer).

These are the three types of typical ramp up style. I am not sure how the flow rate would look like to achieve that on the Decent, because no one has done that before, and the flow rate is machine-dependent - depends on the headspace/deadspace the water has to fill and compress before registering any pressure.

So as Andre said above, the only reason why you want to hold the pressure at 0.5 bar (or 1bar for that matter) is because we're trying to emulate what lever does and there's the profile most people are comfortable with/come from.



If the Decent can do all these three, it is a fully capable pressure/flow profiling machine. I am sure it can be done based on how your machine works.

EspressoForge wrote:To me the drawing looks like a Portapresso, so I would assume that 0 marks the time that the device is "flipped" and relatively flow rate is very high to instant.

Could very well be Forge, same thing as both are measuring pressure above puck.

samuellaw178 wrote:Could very well be Forge, same thing as both are measuring pressure above puck.

Haha, just going by the sketch! I only jumped in as I thought I could give some input based on my experience, it's a confusing world as pressure & flow are so tightly related.

My guess at the flow rate would be something like this (not really the numbers, just visually). Blue being flow, purple pressure:


In addition to the graphs and numbers, I think it would be cool to see overlays with the delta changes, similar to roasting software out there, as I find that the slope of the graph is often more important than the actual position. But I know further improvements will come later to the UI as John mentioned.

Just wanted to weigh in that this machine has been very interesting to me (as I'm sure it has been to many others), and from what I can see he has built a great platform, especially as a lab type device for seeing just how much a variable matters in espresso extraction.

John: something I haven't heard a lot about, the temp profiling. What is the range of adjust-ability there? We've been seeing a good amount lately on the min/max capabilities of pressure, next logical progression is with temp!

EspressoForge wrote:John: something I haven't heard a lot about, the temp profiling. What is the range of adjust-ability there? We've been seeing a good amount lately on the min/max capabilities of pressure, next logical progression is with temp!

You should be able to adjust between ~80°C and ~99°C in near-real time (ie, ~1 second delay). Faster flow rates are much more accurate than slow ones (under 1ml/s) .

I haven't played at all with per-frame temperatures: you can have up to 6 "frames" or steps to your shot, and each frame can have its own temperature. I haven't programmed the gui for this yet, but I will in the next few weeks. The firmware already supports this.

As to the shot experiments above, and also temperature profiling experimentation, I need to push back on the ideas above for now, because I need to focus on making the tools (shipping the DE1/DE1+) so that those of you who buy one of these machines do the experimenting.

Remember my metaphor of "I'm the instrument builder, you're the musicians" ? I'm really just an average barista who happens to have a cool tool, but really my strength is in tool building, and I'd rather leave the experimenting to you guys.

I tried a 0.36 and 0.6 flow rate this morning, with a long preinfusion, and got lots of channeling and gushing. I'm sure a finer grind, as you guys indicated, would help, but experimenting with that doesn't pay the bills, nor does it get machines shipped, so I need to put that aside for now.