Group Head Pressure-Test vs Shot?

#1: Post by **kjcavet** » September 25th, 2023, 8:53 pm

I get 10-10.5 Bars as per the gauge (on the group head) on my Rocket Appartamento during a blind filter test but it only reads 4.5-6 Bars when pulling a shot.
Is that normal?
Maybe I should know the answer but I am unsure.

#2: Post by **Jeff** » September 25th, 2023, 9:05 pm

Welcome to H-B!

With a properly ground and prepped puck of fresh coffee, the peak pressure shown during extraction is often limited by the OPV pressure.

That you were seeing much lower pressures suggests to me that the grind is too coarse, the coffee is stale, your puck prep is poor (and you're channeling), or the grind is too fine and/or the basket is overstuffed and you're channeling.

Assuming you have a bottomless portafilter, would you post a video of one of your shots on something like YouTube and link it here?

September 25th, 2023, 9:16 pm

Thanks for the reply. I think my prep is good & channeling isn't obvious. I'm using a super fine grind because flow rate is fast. Dose is 18.5 in a dbl shot basket.
I've never posted anything on Youtube but I'll try.
Sometimes even with the finest grind the flow is too quick for proper xtraction. I wonder if this is the issue, pressure?

#4: Post by **Jeff** » September 25th, 2023, 9:19 pm

If you're using Lavassa that has been open more than a day or so that may be a significant part of the problem. With good quality coffee and the Sette grinder, you should be able to choke your machine entirely. If you post the grind setting that you're using, someone with a Sette may be able to give you a good idea if you are surprisingly fine.

September 25th, 2023, 9:31 pm

I'm using Caribou & I ground it on 1C last time. I'll keep experimenting.
Thanks.

#6: Post by **Jeff** » September 25th, 2023, 9:38 pm

When was it roasted? When looking for coffee for traditional espresso, most people here ignore anything that has only a "best by" date as well as anything that is more than a couple weeks since roast.

(Classic Italian blends from the best Italian roasters and very light "filter" roasts are notable exceptions with different guidelines.)

#7: Post by **JRising** » September 26th, 2023, 7:59 am

The gauge reading while brewing against the blind basket is nice for proving that the machine and the pump in particular are fine. The gauge reading while brewing against your "puck" is an indication of the coffee preparation. If it's way too low, then the water is just gushing through the puck and probably not extracting much.
When the pressure is obviously too low you can keep the grinder set to the same coarseness but dose a half a gram more, see the effect, taste the effect and then decide of you want to go back to the previous weight and set the grind slightly finer, to see and taste that effect.

If it chokes off the flow, then the gauge will show the max, same as when the blind basket chokes the flow.

September 26th, 2023, 8:44 am

Thank you. I'm going to re-examine puck prep, grinding & freshness until it gets there. It may very well be one of those sometime things (certain beans/freshness) because I was hitting 8-9 Bars. Recently, I replaced the pressurestat with the new type to resolve an issue but that shouldn't be the cause.

#9: Post by **Pressino** » September 26th, 2023, 9:52 am

You could try setting your grinder to its finest grind setting and dose and prep your puck as normally do. That should definitely choke your machine, regardless of how stale your coffee is. If it doesn't, you have a problem with your grinder. If the machine chokes at the finest setting, gradually grind coarser until you find a setting that gives a good extraction time. If that shot doesn't taste OK, the problem could be bad/stale coffee, improper brew temperature, or poor burr alignment.

September 28th, 2023, 8:14 pm

The beans played a part but the main culprit was the grind.
It was time to adjust the burrs on my grinder. After installing a shim all was well.
Thanks