Pre-infusion tests results

[slo]

After making a few conmments on pre-infusion (P/I) without knowing what I was taking about (I was just relying on what I read on the subject), I decided to actually do a few experiments of my own and share it with you.
Basic experiment set-up:
Water main pressure, measured at the group head, builds up in about 3 seconds from 0 to 56 psig, stable after.
Shot weight is 16 +/- 0.1 grams of decaf espresso blend (scale accuracy 0.1 gram).
Tamper load 30 lbs, using Espro click convex tamper.
Tamping done with a nuttating motion prior to full load tamp. I almost eliminated side channelling with this. Still learning!

BTW: Did you guys ever stop to think that when you use a 30 lbs load on a 53 mm surface you apply a pressure of 8.77 psif while the 58 mm portafilter guys are applying a pressure of 7.33 psif. Remember that the Vivaldi people apply more pressure when tamping with an Espro. Just a thought. Actually never read this anywhere.

Anyway back to the experiment:

First picture is with P/I set at 3 seconds using old grinds collected from stray and end of session clean up. I put it in because as you can see it absorbed the water differently. Just making an illustration about the difference between fresh ground and old ground.

3 seconds old grinds.jpg (42.92 KiB) Viewed 24618 times

I keep on sidetracking... From now on with fresh grinds.

The next picture is with P/I set at 3 seconds.

3 seconds fresh grinds.jpg (40.26 KiB) Viewed 24616 times

As you can see there is less penetration with the fresher grinds.

The next picture is with P/I set at 6 seconds.

6 seconds fresh grinds.jpg (46.85 KiB) Viewed 24616 times

Clearly the whole is saturated. There was a beginning of a pour (a few drops in the cup) with this setting even without the pump running.
The next picture is with P/I set at 6 seconds again I was verifying that the previous was not a glitch.

6 seconds fresh grinds repeat.jpg (39.62 KiB) Viewed 24616 times

The next picture is with P/I set at 5 seconds.

5 seconds fresh grinds.jpg (40.09 KiB) Viewed 24616 times

As you can see the puck is almost fully saturated with only a very small dry spot on the bottom.

More on the next post limit of 5 attachment per post!!!

[slo]

Tests results continued...

I repeated with the same 5 seconds setting and got pretty much the same results. Very repeatable.

5 seconds fresh grinds repeat1.jpg (43.84 KiB) Viewed 24615 times

5 seconds fresh grinds repeat2.jpg (36.85 KiB) Viewed 24615 times

One thing that most be noted is that I get darkening or slight drops build-up around the edge of the basket just before the pump kicks in with all the above 5 seconds experiment.

The quality of the pictures is not always there but I think that it is enough for you guys to get the point.

Conclusion:
With my 56 psig main line pressure a 5 seconds pre-infusion setting give a fully saturated puck.
The puck will not be saturated with a 3 second pre-infusion at 25-30 psig as suggested as a starting point.
Now this does not say anything on the taste. As you can guess none of these were tasted shots. Since I am still playing around with my new Vivaldi, I will not comment on taste just yet

[JohnB]

This would seem to jive with what I posted & the H-B results of 6 seconds at 3 bar(43.5psi). I'm surprised that your line pressure takes 3 seconds to build up. So you see 0 pressure on the machine pressure guage until you hit the button? My guage reads line pressure(38 psi) all the time & it doesn't change when I hit the brew button until the pump kicks in. I would still consider a pressure regulator that would allow you to lower the line pressure abit.

[slo]

Yes it does!

When I mentioned "Water main pressure, measured at the group head, builds up in about 3 seconds from 0 to 56 psig, stable after." I meant really measured at the group head with an external pressure gauge mounted on a portafilter apparatus.

Here's the apparatus:

pressure apparatus.jpg (64.11 KiB) Viewed 24587 times

The main pressure shown on the machine pressure gauge is indeed always there and does not budge until the pump starts. Also 3 seconds is with the portafilter apparatus already full of water.

It is actually the first time I measured the main pressure at the group head. I was kind of surprised it was so high. I had taken the pressure at the external hose outlet around the house with another gauge and had found the pressure to be more like 45 psig.

Still, I am sure that a regulator is required. Remember the question I had posted about the need for a regulator? No one, other than you, answered, Since I have no leaks and don't know that CC recommendation is related to anything else than leaks, other than pressure fluctuation, I still don't see a benefit for the investment.

That being said, I will monitor the main pressure for any significant fluctuations. If anyone has an answer to that question please be so kind as to educate me. I would greatly appreciate.

[wgaggl]

I had a pressure regulator
1) to increase consistency; on a hot summer day when everyone is irrigating their lawn the main water pressure drops from approx 4.5bar to less than 4 bar in our area. That pressure difference also affects the brewing pressure (with or w/o PI) and with it the grind (to keep the shot time the same).
2) We have approx 4.5bar here, which is pretty high for preinfusion; I have my pump set at 8.5bar, so 4.5bar would be more than 50% of that.
3) But the lower the line pressure, the slower the PI and the more gradual the rise in temperature. As I noted here viewtopic.php?f=20&t=558 somewhere down the thread I believe this is a limitation of the S1 passive group design: You are not just affecting brewing pressure but also substantially the temperature profile during the first third of the shot.
As been discussed here viewtopic.php?f=47&t=914#p14546 this changes the flavor profile and can bring out unwanted flavor components especially if you like light to medium roasts (which is basically all of my own roasts).
As a recent example where I abandoned preinfusion is Intelligentsia BlackCat since they made changes to their blend this July. It actually tastes slightly sour to me with PI, then I had to increase the brewing temp. As Niko noted somewhere another remedy could be underdosing a triple basket to allow for a better dwell. But that still gave me less body.

So if I used PI at all I usually keep the time low and with that condition you generally will need more than 2bar line pressure. This is easy to test with a bottomless PF, just do your PI at a certain pressure and desired time, if you don't see coffee drops appearing at then end of PI, you either have to increase time or line pressure to saturate the puck (which is the purpose of PI) before the pump kicks in.

W.

[JohnB]

Ok, now I see what you meant. Hard to tell from your pic but can you adjust the flow through your set up to get an accurate group pressure reading simulating an actual shot? i.e. 2 oz in 25-30 seconds

Heres my pressure guage set up:

116-1619_IMG.JPG (115.79 KiB) Viewed 24577 times

[wgaggl]

...but then you also need to fill up the volume in the basket that is usually occupied by coffee with something else; simulating the flow by added resistance to the spout isn't fully simulating preinfusion.

W.

[JohnB]

As been discussed here viewtopic.php?f=47&t=914#p14546 this changes the flavor profile and can bring out unwanted flavor components especially if you like light to medium roasts (which is basically all of my own roasts).
As a recent example where I abandoned preinfusion is Intelligentsia BlackCat since they made changes to their blend this July. It actually tastes slightly sour to me with PI, then I had to increase the brewing temp. As Niko noted somewhere another remedy could be underdosing a triple basket to allow for a better dwell. But that still gave me less body.

So if I used PI at all I usually keep the time low and with that condition you generally will need more than 2bar line pressure. This is easy to test with a bottomless PF, just do your PI at a certain pressure and desired time, if you don't see coffee drops appearing at then end of PI, you either have to increase time or line pressure to saturate the puck (which is the purpose of PI) before the pump kicks in.

W.

Since that thread you linked to was in 2007 no one had p/i but you so not much of a discussion. You are the only person I have heard talk about sour flavors with the p/i, personally I haven't noticed it. I'll have to do some back to back shots at the same temp with & without the p/i & see if I notice any sourness. If you've done a warm up flush & the offset is set correctly the first few seconds of the shot should only be marginally lower then the set temp. Its hard to believe that would throw off the entire shot. Since I now own a Scace Device I'll have a new excuse to do some more testing.

[JohnB]

...but then you also need to fill up the volume in the basket that is usually occupied by coffee with something else; simulating the flow by added resistance to the spout isn't fully simulating preinfusion.

W.

I'm not trying to simulate p/i & its never turned on when I test/set group pressure.

[wgaggl]

Since that thread you linked to was in 2007 no one had p/i but you so not much of a discussion.

It doesn't matter that I did it in 2007. The Omega timer module was set up to delay the pump for a certain time after the solenoid engaged. That's what the VII preinfusion does.

You are the only person I have heard talk about sour flavors with the p/i, personally I haven't noticed it. I'll have to do some back to back shots at the same temp with & without the p/i & see if I notice any sourness.

Others have noted viewtopic.php?f=47&t=914#p14546 that "line-level preinfusion was detrimental to flavor" especially in light-roasted coffees. If that's about 'sour' tastes or some other defect depends on coffee, grinder setting, and of course subjective taste results. Maybe I'm just biased against some flavor components more than to others...

If you've done a warm up flush & the offset is set correctly the first few seconds of the shot should only be marginally lower then the set temp.

C'mon John, with my history here you should assume that I am doing that right.

Its hard to believe that would throw off the entire shot.

I mentioned it affects the first third of the shot; it's a common method to divvy up the pour in thirds for profile testing and compare how the profile develops. And of course the components of the first third will be part of the end product.

Since I now own a Scace Device I'll have a new excuse to do some more testing.

Please do so, I'm interested to discuss results. I'm not sure however how the Scace Device reflects what's going on during preinfusion, as there's no puck to get saturated.

Cheers,
W.

[JohnB]

[quote="wgaggl
C'mon John, with my history here you should assume that I am doing that right.

Since I now own a Scace Device I'll have a new excuse to do some more testing.

Please do so, I'm interested to discuss results. I'm not sure however how the Scace Device reflects what's going on during preinfusion, as there's no puck to get saturated.

W.[/quote]

I mentioned it since you own an S1V1 & as you know it has a very narrow temp offset adjustment so unless your machine falls within that 3°C range it could never be set correctly. I also didn't see a Scace listed in that long list of extras in the linked thread.
I ended up moving from a 0° offset to a +2° setting once I got the expanded offset range upgrade & did some extensive temp testing with a Scace.

I was one of those that posted that I didn't like what P/I does to small dose (13-14g) shots but it had nothing to do with sourness. I felt it washed out/diluted/mellowed some of the flavor intensity I liked. In a large dose shot this isn't a bad thing but I didn't care for it with my small S/O doses.

The Scace will reflect temp changes from beginning to end of shot which is what its suppose to do. It will be interesting to see just how much cooler the p/i water is since that seems to be the issue you have with it.

[wgaggl]

I did most of my measurements back then using a double basket with a tiny hole for the thermocouple and the bottomless PF. This way the temperature can be measured in a real coffee bed and the height of the thermocouple can be adjusted from top of the puck all the way down to the bottom and all levels in between.
Distributing the coffee is a little bit more demanding with the thermocouple buried in the coffee, but it still works without adding much channeling. Real downside is a lot of wasted coffee...

W.

[JohnB]

I did most of my measurements back then using a double basket with a tiny hole for the thermocouple and the bottomless PF. This way the temperature can be measured in a real coffee bed and the height of the thermocouple can be adjusted from top of the puck all the way down to the bottom and all levels in between.
Distributing the coffee is a little bit more demanding with the thermocouple buried in the coffee, but it still works without adding much channeling. Real downside is a lot of wasted coffee...

W.

The Scace uses a mass to simulate the coffee puck & seems to be well regarded for temp accuracy. Following the recent posts concerning p/i on the GS3 forum I'd say you've bought the right machine. No one seems too impressed with the pump driven p/i & they all wish for a line pressure system. If & when I move on from my V2 it would be to something closer to a Speedster then a GS3 even if it means no Autowash function.

[slo]

Sorry to interupt this heated discussion...

To answer John. Yes, there is lever valve on the right of the picture to adjust for flow.

To answer "W.", I hear you on the pressure fluctuation but have not seen any here so far. Also, since you are sayng that increased pressure would reduce the temperature gradient, why would you want to reduce it?

Why is doing your pre-infusion at almost 50% brew pressure bad? It sounds to me a compromise between thoroughly wetting the coffee in a decent P/I period of time and not having thorough P/I of none at all.

Finally, having done my original P/I test with different coffees and seeing first hand that the P/I has varying effectiveness with varying coffees and grind setting, I can confidently say that we will never all achieve the same result and even if we did evaluation of the taste in the cup will always be in the "taste buds of the beholder".

I appreciate all your comments and I am learning from everything I have read so far.

[wgaggl]

Slo, of course it's on the tastebuds of the beholder.
The higher the preinfusion pressure, the closer you get to no preinfusion, no matter what time you select. That's the only point. I don't say 50% is 'bad', but at some pressure preinfusion looses it's meaning... I haven't seen a systematic exploration of that, to see that would be great.
Yes, those subjective tastebuds...
W.

[wgaggl]

Following the recent posts concerning p/i on the GS3 forum I'd say you've bought the right machine. No one seems too impressed with the pump driven p/i & they all wish for a line pressure system. If & when I move on from my V2 it would be to something closer to a Speedster then a GS3 even if it means no Autowash function.

That's why I get the GS/3 Paddle Group in two weeks!
Manual preinfusion, my wife already sees a lot of coffee going down the drain...

[JohnB]

That's why I get the GS/3 Paddle Group in two weeks!
Manual preinfusion, my wife already sees a lot of coffee going down the drain...

Nice choice! Should be one of the first in the U.S. I would think. How does the price compare to what we've been seeing on the old stock blow out?