Low Brew Pressure = Mild = Lever?

#1: Post by **coffee.me** » December 31st, 2008, 11:17 am

Just out of curiosity, I did an experiment once where I dropped the pressure on my rotary to ~5.5bar. That one shot (or two, I forgot) was very round and mild, not what I expected, no sourness (under-extraction) whatsoever; a quite OK shot. On normal pressure (~9bar), got a lot more pronounced flavors (the way I like'm). At ~12bar they were so sharp it hurts, not for me!

IIRC, this experiment was done on the same day, same beans, same dose, same grind and, I think, same temps. Now, can I conclude from this that that's how a lever shot would compare to my rotary shots...round and mild? Kinda unclear, like you can't taste small differences in different beans unless they were very pronounced or you have a very developed palate?

Just curious

#2: Post by **IMAWriter** » January 1st, 2009, 1:26 am

Happy New Year.
I believe it was determined that about 40lbs of pressure downward produces something around a 9 bar pressure equivalent.
I actually used a bit less pressure with the Arrarex Caravel I had on loan for a time. On my Cremina, I like a fine grind, 15# tamp, and with about a 35# downward pressure I get 30 second pulls of 1.25oz
Any less pressure, and I get nothing. A coarser grind gets me 15 second pulls, mostly lightish and skanky tasting.

January 1st, 2009, 3:47 am

Skanky? I have searched and seached through my dictionary of cupping terms and have not found "skanky" anywhere. but I know what you mean, I think. As in "wonderful blueberry muffin essence with a skanky finish". Sounds like a winnah!

#4: Post by **IMAWriter** » January 1st, 2009, 3:32 pm

LMBO!!
Like describing a wine as "young, skittish, yet with as certain benevolence."
Back OT. Are my above post statements useful to our OP?

#5: Post by **sweaner** » January 1st, 2009, 4:32 pm

orphanespresso wrote:Skanky? I have searched and seached through my dictionary of cupping terms and have not found "skanky" anywhere. but I know what you mean, I think. As in "wonderful blueberry muffin essence with a skanky finish". Sounds like a winnah!

I don't know. That skanky girl I was fixed up with in college most certainly did not have a "wonderful blueberry muffin essence!"

January 1st, 2009, 7:43 pm

Happy New Year to all...

I was hoping to get opinions on my little experiment (discussed on the 1st post). Does my rotary's low pressure shot sound like what I should expect from a lever? That is:

coffee.me wrote:round and mild? Kinda unclear, like you can't taste small differences in different beans unless they were very pronounced or you have a very developed palate?

That's why the title asks: low pressure = mild = lever?

#7: Post by **IMAWriter** » January 1st, 2009, 9:12 pm

I thought I sort of answered your posts. I wouldn't describe a lever pull as mild. I think is a nice separation of flavors. I don't think your machine and a lever correlate in this manner.
a very light pull down would yield nothing.

#8: Post by **timo888** » January 1st, 2009, 10:14 pm

Your underlying question is whether reduced brew pressure tends to soften or subdue flavors, not necessarily in a bad way, and I think the answer is yes.

Domestic spring levers produce about 5-7 bars of pressure, and trail off to 3-4 bars as the spring expands. Domestic manual levers produce anywhere from 1 to 9+ bars of pressure, depending upon how gently or hard you pull on the lever. E.g. you might preinfuse at 2 bar and then pull "for real" for the rest of the shot -- 6 to 9 bars.

Regards
T

#9: Post by HB » January 1st, 2009, 11:24 pm

Excellent thread, I'm glad you brought it up.

coffee.me wrote:Does my rotary's low pressure shot sound like what I should expect from a lever?

Yes, if you're referring to a spring-powered lever espresso machine. Participants of the lengthy Lever Espresso Machine Smackdown touched on this point several times; below are two excerpts:

gscace wrote:In order to get both machines more on the same page, I reprogrammed the marzocco's pump on Monday to produce a linearly declining pressure profile, with maximum pressure of 100 psi (measured with a scace 2) and minimum of 50 psi. The pre-infusion was 2 secs at about 30 psi, with a second order (concave up) pressure rise to max pressure taking place over 3 seconds. These values are substantially lower than the 135 psi to 90 psi that i was using, and the shape of the decline is different as well - straight line with increasing time, rather than curved. Shots brewed at these pressure were more similar to the Lusso's. They were somewhat sweeter, but the brighter notes were more muted. I don't have all of the puzzle pieces yet. I still haven't gotten temperature data, and the basket shape has to have some effect. I like the shots brewed from the marzocco at these relatively low pressures. For a while now I've thought that Illy and whoever's canonical 9 bar optimum pressure didn't really hold up to scrutiny because there's no supporting documentation on how the 9 bars gets measured.

<snip>

My opinion of the Lusso right now is that one shouldn't get too hung up on the double pull thing. It's only a big deal if you absolutely have to have big shot volumes. If, on the other hand you're flexible and observant, you can get some pretty killer coffee for your 1100 bucks. The Lusso is very tolerant of coffee. Brightness and distinct flavors are diminished compared to my benchmark machinery. Whether or not that is your cup of coffee is up to you.

HB wrote:Since this is a "Smackdown", I'll loosen up and toss out a completely unsupported assertion: The combination of the high "humped" brew pressure profile, smoothness of the brew pressure, and lower/declining brew pressure of spring-powered lever espresso machines are the major factors contributing to the enhanced clarity and smoothness (Andy, sorry for using that word!) frequently noted in lever machine discussions. Manual lever machines operated by a skilled barista will produce espressos that are equivalent to their pump-driven cousins in terms of crema / body.

Which produces a "better" espresso? A pump driven E61 like the Vibiemme or spring driven lever machines like the Microcasa or Lusso? It's a loaded question, I know...

If high body espresso with loads of crema volume, gorgeous color, and rich consistency are your thing, it's an easy win for the E61 tribe. If it's all about taste, the answer is less definitive. In my opinion, some blends play to the strengths of lever machines. For example, Espresso Havana morphed under the influence of the spring-powered lever, becoming a brighter, fruitier blend with subdued tobacco notes. That is, a darker roasted coffee that I'd expect to have less varietal characteristics brewed more like its lighter roasted counterpart. On the other hand, so-called "comfort espressos" that are very popular these days (lots of chocolates, heavy body) play against the spring-lever's strengths and right into the hands of the E61 crowd.

So which produces a better espresso? Unsatisfying as it may be, my answer to-date is: It depends on what espresso characteristics you treasure, and what blends you typically choose.

As a group, owners of pump driven espresso machines don't consider brew pressure with the same interest as brew temperature. For example, home baristas will bracket brew temperatures to learn how the taste profile changes; few will manipulate the brew pressure. That's probably because it's not easy to tweak on most espresso machines, and probably because some are unwilling to sacrifice crema/body at lower pressure. I think it's worth trying, e.g., brew pressures of 7.5, 8.5 and 9.5 bar.

PS: If you're hungry for reading material on the subject:

Brew pressure and its effect on espresso
Experiments in programmable, variable brew pressure profiling (gscace)
Brew pressure profiling update 2 (gscace)
Brew pressure profiling update 3 (gscace)
Playing with Pump Pressure: Part Uno (AndyS)
Playing with Pump Pressure: Part Due (AndyS)
Lower pressure brewing

#10: Post by **IMAWriter** » January 2nd, 2009, 1:30 pm

Excellent post, Dan.