Why Does a Long Pre-Infusion and Extraction Work? - Page 3

Beginner and pro baristas share tips and tricks.

#21: Post by okmed »

@ Baldheadracing

Interesting. I had considered at one time replacing the existing boiler pressure gauge with a dual pressure gauge to do what you have done, but I couldn't find one the same diameter as the original and didn't want to enlarge the opening making it a irreversible mod. My Strega is plumbed in and I put a toggle switch in that allows me to take the micro switch at the lever out of the circuit. I then just adjust my dedicated water pressure regulator to 2.5 bar which becomes my pre-infusion as the water just passes through the vibe pump if it's not turned on.


#22: Post by mathof »

baldheadracing wrote:So ... it was bugging me that Mr. Gunson's recommendations were the opposite of mine for pre-infusion pressure. So I tried it his way... For a long pre-infusion of, say, 30 seconds, a higher pre-infusion pressure like 6 bar needs an incredibly fine grind to last 30 seconds without starting extraction (beyond sweating), which leads to what is called "back-end blow-out" where the visible flow greatly increases early in the extraction, early blonding, etc
If you want to imitate Reiss's method, you might consider trying a considerable shorter pre-infusion time at 6 bar. Here is what he wrote on his forum in 2018:

"I would suggest that for a light nordic style single origin roast you might expect to wait about 12s before the first drip falls in the cup during pre-infusion. Once the first drip falls in the cup simply release the lever"

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cskorton (original poster)

#23: Post by cskorton (original poster) »

I've experimented quite a bit with my LR's various preinfusion pressures based on something very subjective...my own tastes. My findings are consistent with Reiss's recommendations. Again, though, this is purely based on my tastes!

Very dark, and/or high robusta blends work best with low and short preinfusions. I've found 1.3 bar to be the sweet spot with the lowest allowable preinfusion time to allow the group head to fill. 1 bar for me was always a bit too low.

On the other end of the spectrum, light roasts (maybe not quite Nordic roasts) like 3 bar preinfusion best, at most for 15 seconds. I haven't experimented above 3 bar because based on my tastes, it wasn't necessary. Same thing with pushing preinfusion times longer than 15 seconds.

That's actually why I was so confused and why I started this thread. I couldn't understand how I could push the coffee so hard and long and still get great tasting espresso.

That's why I was hoping someone could guide me through the theory of super long preinfusions so I can figure out which beans to push harder and how.