Alchemist wrote:Well, I couldn't help myself. Even with a leak, I had to try a theory out. So I have pulled a few shots on the modded lever, then applied what I "learned" to my other two.

What I found is something I have been looking for. Target consistency in texture. I recall from tasting some shots from the infamous Versalab espresso machine that the texture (as well as taste) was just amazing. Liquid molten silk and butter. He "only" had a dial gauge, and there is a somewhat natural lag in that response, but I seem to remember the pressure did not spike instantly. It profiled up smoothly much like I profile my pressure ramps on my HPLC columns at the lab.

Keeping those things in mind, I tried a profile that ramped the pressure at the puck to about 9 bars over 3-4 seconds (after pre-infusion) and then maintained the pressure at the puck instead of letting it drop as constant pressure applied tends to do. What results is a flow that actually comes out faster (columns hit with pressure tend to compact and collapes increasing the pressure needed to push a give flow of water through). From experience (zen like) I start a 2nd ramp of my applied pressure just before flow is expected.

What results is this kind of pattern. BTW, this is a completely simulated graph to show what I mean, not actual recorded data (it's too nice). Also, the pressure applied is just a rough guess, to give an idea of the extra pressure applied.

image: userpix/661_simulated_pull_1.jpg

Oh, and what does this mean and why am I giving it? Well, over the last three days, I have tried this profile (from muscle memory only) on my Gaggia Factory and Cremina, 4 shots in a row on each. What resulted is liquid molten buttery silk. Shot after shot. The flavor shifted here and there due to temp, bean and other fluxes, but the crema (near 90 %) and texture were amazing and consistent. Let the puck pressure "drop" by not increasing my force or hitting the puck instantly with pressure and the texture went away.

So, with that in mind, please, someone(s) give this a try and see if there is a significant difference. BTW, Cremina owners. Try both hands on your lever. It makes the pull way easier and the machine does not tip. I find no hand necessary on the PF handle.

I have tried making a few shots with the increase in strength on my pull as the shot progressed. It definitely made a difference in the overall quality of the texture and taste. However I am not sure if the pressure in the chamber was also increasing or with the flow beginning more strength was actually needed to maintain the pressure.

In either case the taste in the cup is what counts and I will continue this method. Alchemis, thanks for the experimentation. It is definitely helping my technique.

Good luck with the welding.

I am going to let Alchemist John load the commentary and the data. Needless to say, we got buzzed on Espresso today and learned alot of lessons. I want a gauge on the top of my machine! I have to figure out how to load video on this sight. I'll go ahead and load some still pictures. John and I went through more than a pound of coffee today! I must say, we had fun! Oh and I learned a lot!



Who says you can't get crema from a lever?

Les

OK I think I can post a movie. This is off of my website. I tried a gvideo, but it wouldn't work on my Apple. So I am back to the laptop. I see Alchemist hasn't posted. We found out many very interesting things about how pressure works on the shot. Well here is the first video.

http://www.thortamper.com/alchemistmovie.html

Les

GreatDane wrote:OK I think I can post a movie. This is off of my website. I tried a gvideo, but it wouldn't work on my Apple. So I am back to the laptop. I see Alchemist hasn't posted. We found out many very interesting things about how pressure works on the shot. Well here is the first video.
Les

Thanks Les. It was a fun day. And it was a bit closer to 2 lbs of coffee it turns out. We went through all but 2 oz of my 22 oz, and half of your pound.

None the less, yesterday was in my no where near humble opinion HIGHLY instructive on so many levels. In many ways we found patterns and correlations which I find terribly helpful and in some ways way more instructive than written in stone "facts".

Some background: We of course used the pressure modded LaPavoni 16 cup, but also attempted to translate (successfully I think) some of the information to my other two levers - my Gaggia Factory and Olympia. We used Les's Major Mazzer for grinding and kept the grind consistent once dialed in so we were not changing multiple variables. Also, I don't recall the espresso blend that Les brought, but mine that we did most of the tasting notes and tests on was a 1/3 blend of SM DP Ghimbi, DP Harrar Lot 30, DP Sidamo, 4 days rest, 15.5 minute drum roast.

Where to start? How about some taste vs pressure notes. I am going to work in psig and let folks translate as needed. The LP is a 49 mm basket, in which we used a double Elektra basket. We started at below what some springs are listed at at brought it up to 180 psig. In all of these tests I tapped the PF to settle the grounds, basic leveling and tamp pressure of around 40-50 lbs. What more do you want to know? I did all of these pulls and did not particular watch the pull - I watched and adjusted based on the gauge pressure. In all cases I had to increase my effort midway through the pull as previously mentioned.


80 psig - Copious light crema. Low toned and soft on the palate. No particular fruit present. Oddly flat taste, but generally completely drinkable.

90 - Virtually no difference from the above

100 - More of a rounded flavor profile. Crema was still soft and collapsed quickly. Flat taste was not present.

120 - The crema thickened up and is gaining its normal reddish tint. There is aroma of fruit and chocolate in this shot that was lacking before.

130 - This shot felt like a "normal" pull. The Crema was denser, red in color and stable. The flavor had blueberry notes I associate with this blend, as well as chocolate and peatiness.

140 - Lots of tigerstriping in this shot. This shot tasted of coffee - strange but true There was a little less low tones, a little more fruit, but very balanced.

150 - This shot was very difficult to hold steady from a physical stand point. Felt like I was trying to shot a moving target. Was the puck dynamic changing The flavor on this shot was just odd and mis-balanced. We tried it a couple times and the results were the same. Less high end notes, sharp low end flavors.

160 - Based on post conclusions, at this level the puck was starting to collapse and inhibit flow. Volume was greatly reduced over the timespan of the above shots (22-28 seconds). No mouse tails, but extremely thick crema in a deep red. Creamy mouthfeel but sharp and sour.

170 - The shot started off ok, but as soon as the pressure hit 160 the puck collapsed and flow dropped - not worth tasting.

180 - Silky in texture, but sharp. No low notes. Heavily restricted flow.

I won't micro analyze some of the obvious conclusions from above. But I will add a few other tests we performed in reference to what we think was the collapsing puck. In all the shots above I took 3 seconds after preinfusion to reach my target pressure. In two cases at 130 and 140 I attempted to hit the puck with instant target pressure. In both cases (as expected) the puck collapsed and flow radically dropped off to a stalled shot. Again in both cases if I applied 40 psi, flow was easy and unhindered. The shot was ruined, but I could release the PF without a sneeze from hell. In a similar thought we tried a couple 180 psi pulls but took 5 and 7 seconds to reach pressure. In both cases once 160 psi was reached, the bed collapsed and flow dropped.

All this brought me to a number of conclusions that I have always suspected and that others have mentioned also. A espresso puck is nothing more than a high pressure chromatography column and it behaves EXACTLY as ones I use at work. They work best and as "designed" if treated gently to pressure spikes. They collapse and become unusable if spiked with pressure. They have an upper pressure limit that no amount of gentle pressure gradients will let you get past without hurting them. Depending on the pressure applied to them, items retained on the column (coffee and aroma flavors in this case) are released differently.

General conclusions as I and Les came to them:

1) Lower pressure is better (for flavor and drinkablity) than high pressure.
2) Don't "slam" your puck - treat it gentle when bringing it to full pressure. (BTW, no amount of pre-infusion changed this 0 - 60 sec). I used 3 seconds to great success. Longer didn't help or hurt, I didn't play with shorter except with slams.
3) If your flow begins to decrease drop your applied pressure, don't increase it. Sort of like steering into a slid - counter intuitive.
4) "More" is not better - more is just more

These are some/most of the high points but we played and pulled for 4 hours so please see if you can tease more out of us.
===
Oh, after re-reading, I have a couple random thoughts. The low pressure shots were "blonde" but did not GO blonde, they simply were blond. I propose that it takes a critical pressure to release the color (and some flavor) components from the coffee bed matrix. And as for "going" blonde in a shot, I suspect it is "pockets" of lower pressure or the pressure dropping, not the puck necessarily overextracting.

We both also noted how difficult maintaining a constant pressure really is with and without feedback. I realize now I would like to have tried some "blind" pulls and had Les record them for me to review. Les's one blind pull started at around 130 psi, bounced a bit, ramped to 160 (where we noted his flow "quivered" in instability) and then came back down to 140.

Thanks John! We did have a lot of fun and learning. What was amazing to me was the difficulty of telling the difference between a 120 psi shot and a 140psi shot and the flavor difference between 120, 130, and 140. Experiencing the pressure dip that John talked about in his earlier posts was really a strange sensation. Just about when you feel you have a nice steady pressure established, the flow through the puck increases, the lever starts moving easier, and you have to increase the pressure by your hand on the lever by about 20% to keep the pressure at 140 psi. I would say, the best shots we pulled were in the 130 - 140 psi range. Interesting that it is bettween 9 and 10 bar! With that said, pulling shots on the Gaggia Factory and the Olympia Cremina were transferable from the Pavoni. I had great tiger stripped shots this morning from my Cremina. For the first time, I anticipated the pressure dip and properly corrected for it to maintain the proper shot. It is counter intuitive. You think you should let up on the pressure because the lever is moving faster. However the goal of a great shot as I learned is not to keep the lever moving at the same speed through the shot, but to keep the pressure steady! Another interesting note, is that when you hit that spot with increased flow and push a little harder, the lever slows down to about the same pace it was at before the increase. In some respects what we learned is the harder you push past the 140psi level the slower the shot. If the Pavoni hadn't run out of water and we hadn't been so buzzed on coffee, I think our next experiment would have been to play with the grind. I need to get my grinder pitch in again. We began our shots with my standard espresso grind and adjusted down just one bump on the Mazzer Major to get it just right. I am sure we could have done the same on John's fine handgrinder the Trosser. There is no way we could have done this research with less than a Rocky in my opinion and having the infinite adjustment of the Mazzer made it that much easier. I drank some of the best shots I have had in a long time yesterday. The 3 second ramp is what I think does the most amazing job of getting the best flavor extraction. Some time this week, I am going to get my SAMA spring loaded lever out and try something different. Instead of just priming the pump and letting the lever go for the spring to do its work, I am going to ease off the spring and try letting go gradually over a 3 second period to mimic what we did with the gauge. I will post some more video when I get home from work tonight. I have a good video of a close-up of the gauge during a proper pull. For those interested, my espresso blend was a post roasted blend of full city plus Uganda Bugisu blended 50/50 with full city Ethiopian Lekempki both roasted 16 minutes and rested 6 days.

Les

Sounds like you both must have been quite buzzed after this experiment.

The results are interesting. I was happy to see that the best taste came from the nine to ten bar range. Imagine if the taste was better the harder you pulled. We would all have to start weightlifting. I was wondering how did you compensate for the legendary overheating of the grouphead after repeated shots.

I enjoyed the movie and like the idea of my machine involved in this espresso history in the making. Hey Alchemist, I seem to remember the bakelight handle broken when I sent the machine to you. Did the shipper repair it in transit or have you done a kind deed.

By the way, I have a friend visiting me from germany for a few months. Quite an international artist and has seen many different things along her travels. She thinks we are all over the top. . However, whenever she drinks coffee at my home or studio the smile on her face makes all this research and collecting and searching and obsessing....... very worthwhile.

John, Les, and happy tamper,

Thanks!!!

Those bits of information are priceless! You have hit on solutions to some questions I've had. You put the data, from your posts and viewpoints, into a form useful to me. I believe information gained by your "Gauge" is one of the best things that has happened to improve my performance as "a guy who sometimes pulls shots" since joining.

I believe that I understand you folks to have said:: A constant brewing pressure during pulls may well be the defining factor of good espresso flavor. That pressure would be determined by the Barista to bring out subtle differences of roast and bean for any particular palate???

Of course temp and grind will make a difference.
Did the increasing heat of the group make much difference in quality of the brew?

See, mommy, there is a use for totally "useless" mods, the gauge rocks!!

Thanks Again to all!
sincerely
Richard / espressme

OK here is some more video that I think will help you catch the profile better. To answer the overheating there is a very good pressure gauge and an on off switch. By keeping the pressure at about 1.2 bar in the boiler we didn't have overheating issues. I think I am going to do something about the PF handle before it comes home too!

http://www.thortamper.com/alchemistmovie2.html

Les

happytamper wrote:Sounds like you both must have been quite buzzed after this experiment.

The results are interesting. I was happy to see that the best taste came from the nine to ten bar range. Imagine if the taste was better the harder you pulled. We would all have to start weightlifting. I was wondering how did you compensate for the legendary overheating of the grouphead after repeated shots.

I enjoyed the movie and like the idea of my machine involved in this espresso history in the making. Hey Alchemist, I seem to remember the bakelight handle broken when I sent the machine to you. Did the shipper repair it in transit or have you done a kind deed.

By the way, I have a friend visiting me from germany for a few months. Quite an international artist and has seen many different things along her travels. She thinks we are all over the top. . However, whenever she drinks coffee at my home or studio the smile on her face makes all this research and collecting and searching and obsessing....... very worthwhile.

The overheating was bad for a bit until I got into a routine of short burst of flushing water. That really seemed to keep it in check. The really bad part was how quickly the handle of the PF heated up. I had to start using a towel so the brass would not burn me. Very short handle.

The handle is now fixed thanks to Les, and I also fixed the leaking overpressure valve.

I guess it is about time for it to come home. I really appreciate you letting me experiment.

So, last chance anyone (at least for me). Does anyone want any more hard data or testing?

Looks like my La pavoni is coming back from a spa treatment. Alchemist, Thanks for the great mod and all the experiments.

I will be happy to be using it again soon with all this new data.

And another big thanks to Les for the modded lever handle.

I also noticed the difficulty with the short handle on the portafilter. Kind of a silly size to put on a part that heats up so much. But the machine always made great coffee so i never really thought about it. And I also never made almost two pounds of coffee in one afternoon.

I am glad you guys had a good time with it. If your neck of the woods was closer I would have enjoyed the afternoon experimenting with you.

All the best for the holidays,