To pre flush or not- that is the question

Beginner and pro baristas share tips and tricks for making espresso.
Vindibona1

#1: Post by Vindibona1 »

I'm getting closer to finding my "recipe", but there are so many possible variables that it's hard to now which one to adjust I think I'm pretty close with my dose, grind level and "base" temperarture. I have a Gaggia Classic with PID and changed all the other changeable parts and us an ISM 18gram basket.

As of late I have been doing a pre-flush of 5 seconds with the idea that the water temp hitting the puck will be more consistent throughout the pull. Right now temp on the PID is set to 202° and after the pre-flush drops to about 195 and maybe drifts back to 197-198 during the pull. I've been keeping data.

Just moments ago, I did another test, same everything except I dropped from 17.5g to 17g. Same time as the last one, but so bitter. The only thing that I can think of is that it took me a few more seconds to get the PF up and cup and scale situated. Again same 26 sec time, but way worse than the previous one. I could be tamping a bit too hard, but only going as hard as to make the puck feel solid. The puck was dry coming out but no markings on it. Usually my pucks are a little wetter. I'm waiting right now for the machine to make sure it's up to temp and will do one more with coarser grind and making sure the tamp isn't too hard. Stay tuned for a moment.

Same thing as before. 18.5 seconds. But something was making the pump "pulse", which is what has sort of led me to believe that it might be close to a time with a more robust machine. It didn't "pulse" the last two days, but it wasn't the first time I heard that. But it didn't do that with the 17.5g and one notch finer grind. I'm so confused.

GDM528

#2: Post by GDM528 » replying to Vindibona1 »

I've tried pre-flushing to get the water in the boiler circulating, which in turn should make the internal water temperature more uniform - but the resulting oscillation in the PID was making things net worse. I've ultimately settled on just giving my GC 10-15 minutes to warm up and stabilize.

Your PID setpoint is much lower than mine, which is 106C/223F. I think other GC PID owners set theirs a bit lower than my settings, but still notably higher than your settings. I based my setpoint on measuring the temperature of the water inside the puck inside the basket during a shot. It took a hacked filter basket to do this, but was very informative for how big the drop is from the PID setpoint and how long I wait for the boiler to stabilize. I've been trying to hit 96C/205F brew temperature based on what I've read on the internet as the optimal range.

Vindibona1 (original poster)

#3: Post by Vindibona1 (original poster) » replying to GDM528 »

I used to set the temp to 212F, but having watched videos recently I see they're down closer to 195F. Now the PID is set to 202. Even with the PID this is still a bit of a guessing game. My Gaggia is 5 years old and I'm wondering if it's time just to move on? I don't know how much more consistent I myself can try to be? I think the last thing I'm going to try next week it dark roast beans (La Colombe Corsica). My previous machine as a refurb Saeco Sirena (without pressurized PF) and things seemed so much better with grocery store (or Starbucks French) and a cheap Cuisinart grinder. I feel like I'm working way too hard.

GDM528

#4: Post by GDM528 » replying to Vindibona1 »

A funny thing happened after a couple weeks of consistent (and really good) shots from my Gaggia: I got bored. I started experimenting, doing crazy things that might upset the 95C/30sec/normale crowd, but in the process discovered there's more than one 'sweet spot' that gives me an enjoyable albeit different tasting experience. Now my workflow is mostly about avoiding known-bad outcomes, like channeling, and... I can't think of anything else.

My most recent mod to my Gaggia was adding a dimmer for the water pump. That has rescued nearly 100% of what otherwise would have been terrible shots, by allowing me to back way off on the flow/pressure if channels form and the shot runs too fast. I picked the Gaggia for its active hacker community, but if I did move to another machine I think it might be a lever-pull.

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Kaffee Bitte

#5: Post by Kaffee Bitte »

Dark roasts like low end temps. 195 to maybe 200 max. Medium roasts 199 to about 203. Light plays at the high end best so long as you don't hit a flash boil. Mind these are rough estimates. Machines vary quite a bit in temp stability. My La pavoni is similar in that boiler pressure needs to be very hot to hit the right temps at the shower screen. Often it will come down to how you are getting your temps.

Can't remember what thread it is was but search for some steam boiler temp tables on here. It can lead you to a good temp point to set your pid to for a roast you are using at the time. The big thing to figure and the hardest to get a good temp from is the group. I use a temp strip now but was using a temp probe until it broke. Both methods on my setup I consider ballpark. Never could get the thermometer accurate so just spent some time calculating the boiler temp as read from the pressure gauge and the best temp I had for the group head to see what the temp drop from boiler to group was. Didn't take too long to get those ballpark temp readings and boiler pressure to line up for the temp I was wanting. Made temp surfing a lot easier than the flailing of my early years with the LP.

You have PID so you get the ease of setting your boiler temps. You just need to figure the temp drop at your group and let that lead your settings for whatever coffee you are running.

The PID settings you are running now are probably going to work great for that dark roast you have coming up.
Lynn G.
LMWDP # 110
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GDM528

#6: Post by GDM528 »

Kaffee Bitte wrote:Dark roasts like low end temps. 195 to maybe 200 max. Medium roasts 199 to about 203.
Didn't know about the temperature adjustment based on roast level - thanks for pointing that out! Is there someplace I can read up more on this?

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Kaffee Bitte

#7: Post by Kaffee Bitte »

I remember having read many threads a decade ago about temp ranges for coffees. There were many threads in the roasting and lever sections. I guess it's more a rule of thumb. Probably you will see it mentioned randomly throughout many threads but in passing.

It is deeply tied with the sour/bitter flavors. Tastes sour? Try a higher brew temp. Bitter? Try a lower brew temp. Adjust to your taste.

.I personally have enjoyed over the years some coffee from the whole range of roasts but also had plenty of nopes too. As I get older I am shifting back to more medium to medium dark. Used to really enjoy fruity naturals in light but the acidity bites a bit harder now. Also been doing cappuccinos more than straight or Americans. Taste changes. Still get light roasts as a treat, but daily pulls are edging second crack.
Lynn G.
LMWDP # 110
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GDM528

#8: Post by GDM528 »

Kaffee Bitte wrote:It is deeply tied with the sour/bitter flavors. Tastes sour? Try a higher brew temp. Bitter? Try a lower brew temp. Adjust to your taste.

Still get light roasts as a treat, but daily pulls are edging second crack.
Okay, I think I get it. For example, a darker roast can lean toward bitter, which can be dialed back by lowering the temperature. I can adjust brew temp to fine tune the roast level of the coffee.

Speaking of light and dark roasts, I'm currently experimenting with a roast profile that has both light and dark notes in the same bean so I don't have to choose one or the other. In that case I'll have to thread the needle on brew temp.

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Kaffee Bitte

#9: Post by Kaffee Bitte »

Yep. You got it. But there will be grind variance by roast level and bean density. Dark roasts generally need a finer grind than medium or light to get a similar extraction time.
Lynn G.
LMWDP # 110
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Jeff
Team HB

#10: Post by Jeff »

Brew temperature, for me, is the last of the "knobs" to fine adjust, if at all. Grind, dose, and ratio, for me, make much bigger changes.

Keeping the temperature "the same" when you're not intentionally changing it is important.

There's also no hard rules. There's one Italian-style, dark roast that I found that I had to run at a high temperature to make it drinkable for me.