HB wrote:Why the concern about the shape of the brew profile? Is there a taste defect you're trying to correct?

I noticed, repeatedly, that my best shots are the ones where brew temp doesn't go up during an extraction. If I try to be more descriptive, I'd say that shots with climbing temp tend to be a mix of over and under extractions while the flatter temp ones have clearer notes with no extraction defects I notice -- at least most of the time. Makes sense?

coffee.me wrote:I'd say that shots with climbing temp tend to be a mix of over and under extractions while the flatter temp ones have clearer notes with no extraction defects I notice -- at least most of the time. Makes sense?

Not really. Overextraction/underextraction are possible causes of taste defects, not tastes.

Back to the OP, if you want to try a simple experiment, use an old lever trick: While you dose/distribute the coffee in the portafilter, lock in a cold portafilter. That will draw down the grouphead temperature and should flatten out the tail end of the brew temperature profile.

HB wrote:Back to the OP, if you want to try a simple experiment, use an old lever trick: While you dose/distribute the coffee in the portafilter, lock in a cold portafilter. That will draw down the grouphead temperature and should flatten out the tail end of the brew temperature profile.

But wouldn't doing so have the greatest effect on the start of an extraction rather than the end? As the shot progresses, the GH will get up to temp enough not to affect the tail temp much?

HB wrote:Not really. Overextraction/underextraction are possible causes of taste defects, not tastes.

Forget I said over/underextraction, make that mixed bitters and sours

I feel weird jumping in here, as I'm far from an expert on machine thermodynamics (I don't even know if that's the right word), but you're saying that when you pull a ristretto you get too much bitter and sour flavor, but when you pull a normale, you get something more balanced and sweet? My understanding is that that's the standard taste difference between ristretto and normale. By changing the brew ratio towards ristretto, you get less extraction, which brings bitters and sours to the forefront. Is it possible this isn't a temp issue at all? Maybe you just like normales?

It's clear you know a lot about espresso and espresso extraction. Although I don't agree with his conclusion, like ChrisC I can't help feeling you're missing the forest for the trees.

You're not getting the results you want now. If flow rate is so important to the balance you want, why not hold that constant and allow brew time to vary? What happens if you stop a pour prepped as normale/lungo earlier, i.e., at a ristretto-ristretto/nomale ratio?

Your temp/time charts indicate a brew time near 30 seconds. Try 5, then 8 seconds less, and let us know. If you don't hit a sweet spot, you can try splitting the difference and combining a slightly shorter time with a slightly tighter grind.

At worst, you can eliminate flow rate and its effect on the HX temperature hump as the determinative factor.

BDL

It's mod talk time:

coffee.me wrote:Maybe the solenoid can be modded to achieve our objective of bleeding water during an extraction. If I block the solenoid from fully "closing" the exhaust hole when it is engaged during an extraction, it will bleed some water that was meant to to go the the coffee. I would probably also need to make the exhaust hole smaller. Bingo! This won't even affect its function as a backflushing mechanism. Bingo!

I had a number of old used solenoids laying around so I started experimenting with making them bleed during an extraction session. The image above should explain my final idea: dent the exhaust (bottom) hole of the solenoid so it never fully closes, thus leaking water during a pull and simulating a higher flow rate. I then increased my brew pressure to compensate for the extra flow and It worked! Now my machine delivers a slowly declining brew temp profile! I blame Roeland for inspiring me to ruin my old solenoids .

This wasn't a straight forward mod, nor is it perfect as is. The dent on the above solenoid was too large for what it was supposed to do and it leaked too much water making the brew temp profile decline too fast. I put that solenoid aside and used another one, this time making the dent as tiny as possible. This second trial worked and a few ristrettos brewed with the new mod were done with a slow declining temp profile.

This still isn't without shortcomings, but I'm anything but the patient type. For this to be perfect, the water bleed must be adjustable (any ideas?). The next time I do a normale, I think I'll get a brew temp profile that declines too fast ... but we'll see.

It's alright though, my perfect solenoid is still safe and replacing it isn't going to take more than a couple minutes.


But then comes the question: what about the espresso?

HB wrote:Why the concern about the shape of the brew profile?

ChrisC wrote:Is it possible this isn't a temp issue at all?

boar_d_laze wrote:like ChrisC I can't help feeling you're missing the forest for the trees.

Thanks for this, guys, but it's really a difficult question for me answer definitely. I could swear the few slow pouring ristrettos I had after the mod are better, but that could be a placebo effect. Watching numbers on an LCD is way easier than blind tasting espresso, at least for me. I don't recall that the flat vs declining vs U-shaped brew temp profile argument was ever settled. If knowledgeable HBers ever agree that my machine's U-shaped profile doesn't matter, I'll just go back to troubleshooting something other than brew temp profile. But with so much praise for stable profiles, I can't go on looking at my high flying one and do nothing about it. That said, if, after a few weeks, I realize I'm not getting the better espresso I was hoping for, I could easily reverse this mod and start all over.