I jumped headfirst into espresso making a few months ago buying a Rancilio Silvia with PID and a Urbanic flat burr grinder from Amazon. I think I am in over my head.

9 out of 10 shots I make are sour/acidic to my taste and I cannot figure out why. I am trying to tweak the grind to achieve a 25-30 second double shot (40-50 grams out)

I went to Whole Foods where they brew Allegro Espresso Bel Canto. It had notes of cocoa and berries, but when I brought the same beans home to brew, it tastes sour like lemons.

Here is the rundown:

Urbanic grinder, "tuned" with tinfoil to align the burrs and made stepless. I am grinding around a 4 for folks that have this grinder.
I lowered the OPV in the Rancilio to 9 bar and have the Auber PID set to 221 which is supposed to give a 200 degree head temp.
I have a 20 gram VST basket in a bottomless portafilter.

I can get 40-50 grams of espresso out in 25-30 seconds.

Most of the time, the espresso is pretty sour/acidic and not what I taste from when wholefoods brews it. They are dosing 18 grams and pulling a 2 oz shot. Which I think is a 3x ratio.

I have also purchased some George Howell espresso roast with similar results.

What am I doing wrong? I am one click away from buying a Niche grinder as I know my espresso machine should be good enough for a decent shot.

Thanks,
Chris

In my opinion the cause of a "Surprisingly Sour" shot is when it is brewed at too low a temperature. You have the fortunate position of working with a PID in a Silvia, so we can rule out the thermosiphon stall, thermostat hysteresis, blocked restrictor, etc. of many machines.
You have the simplicity of a single boiler that is going to maintain a fairly stable temp, thanks to the PID... So, I would suggest upping the PID setting by 2 degrees and sampling a couple of shots. If they're an improvement, adjust the temp a little higher. If the machine is burning the coffee or visibly blowing steam through it at the higher temp, take it back down, of course.

There are many other potential causes for the sour shot, with a bottomless portafilter you could watch for channeling, do you have a portafilter gauge or any way of testing the static pressure at the group?

baldheadracing wrote: Just wondering out loud - are you giving the Silvia 35 minutes to warm up before flushing for your first shot?

Yes, usually I let the machine get to 221 with the portafilter in place, pull a shot until the boiler drops to 185 degrees, and then wait another 15 minutes to it gets back to temp. I will let it sit longer today.

JRising wrote:
There are many other potential causes for the sour shot, with a bottomless portafilter you could watch for channeling, do you have a portafilter gauge or any way of testing the static pressure at the group?

Ok, I will try raising the temp 2 degrees F.

Yes, I have a oil-filled gauge that connects to the standard Rancilio portafilter.

As far as the shot, it takes 5-6 seconds for the espresso to start flowing and takes another 5-8 seconds for the 2-3 streams to coalesce into a single stream.

I can certainly see when the grind is too coarse or my tamp was off by jets of espresso escaping my cup.

Unscientifically, I put a thermapen at the output of the portafilter and read 199 degrees which I thought was about where I wanted to be?

Chris

No, I am continuously tweaking grind and dose to hit a "good" shot.

I pulled two shots today dropping the PID temp down to 218 and leaving the unit on for 1.5 hours with the portafilter installed before pulling the shots.

The first shot was 20g in 40g out in 16 seconds and was very good
I ground a little finer and the second shot was 20g in and 40g out in 20 seconds and it was slightly sour

Tomorrow, I will try to raise the temp to 223 degrees to get a few degrees on the other side of where I have been.

The 16 second shot should have been under-extracted I thought, but it was decent.

What does this data tell me? Am I chasing a grind issue or a temperature issue?

Thanks,
Chris

baldheadracing wrote:Well, I don't mean to offend, but in most posts like yours, the root issue is distribution of the grounds in the portafilter - I think a bottomless portafilter would help diagnose that.

However, there is your grinder. I've never used one so I don't know how well it works, and I don't think that there are enough of them around to know how much variation in quality there is between grinders - to that end, can you grind fine enough to choke the Silvia?

No offense taken, I am looking for help solving my issue. I sort of jumped into the deep end with this equipment, I was using a Nespresso previously. I am using a bottomless portafilter, I will try to take a video tomorrow. My puck prep is as follows:

grind 21 g of beans
put the portafilter on a scale with a funnel.
Fill to 20g
use a 4 prong tool (paperclip thick prongs) to level the bed
tap slightly on my cutting board to get the grinds below the funnel level
lightly press with a Reg Barber tamper
Brew!
The puck comes out in one piece with a light tap. I definitely have had shots where it was ground too coarse and espresso jets sprayed coffee everywhere. I absolutely can grind fine enough to choke the Silvia set at 9 bar. One of my complaints about the grinder is 16-20 seconds of brew time is less than a 1 degree of rotation of the dial.

Thanks,
Chris

Hi Chris

I just looked at this grinder on amazon, and think that it might be a problem. Certainly, as previously suggested try to grind increasingly finer until you can choke the machine. Taste a few shots as you do this, it should get progressively more bitter.

I think the issue with grinders at this price point is that the alignment is often very poor. If this is the case, you won't be able to grind finer and progressively increase the resistance in the puck to control the rate of water flow. Often, hand grinders are recommended at this price, alternatively you can find something in the classifieds here like a Niche Zero for $500-600.

The VST basket might make things worse too, as it has little resistance of its own. Something like the espresso parts HQ 14g basket (actually more like a 20g basket) might be better, and is available fairly cheaply.