Long post alert!

Nothing I do fixes my shots being super sour. I'm not a total beginner and I know about the variables that should fix sourness: grind finer, higher temp, less coffee in, more coffee out, better puck prep, etc. But nothing I've tried gets me anything except a very sour shot. At this point I'm not looking to make great espresso, just something decent that isn't super acidic. Even something bitter and stale made from old coffee beans would be progress. I've read a lot of posts about sourness here, and on CoffeeForums and Reddit, but the majority are from beginners and simple advice like "grind finer" or "use different beans" is a common answer. I would really appreciate some more specific or expert help to figure out what I'm missing here, or hear if someone has experienced the same thing and found a fix. I don't know if the main problem is equipment-related (Gaggia Classic Pro) or skill-related.

Here are the details about my shots and the variables that should have fixed the sourness:

Equipment
Gaggia Classic Pro with OPV modded to 9 bar, Compak K6 grinder modded for single dosing (very clumpy), original Gaggia basket, bottomless portafilter, tamp or distribution tool. I'm considering getting a better basket just to rule out that variable, but would like it if someone could confirm if an improved basket might fix severe sourness or just make "better" espresso.

Experimental method
When I first got this machine about a year ago, I was scientifically systematic with changing variables. I got discouraged after a while when nothing I did fixed the sourness, and just resorted to milk drinks. I've experimented on/off since then but not with the same rigorousness. So keep in mind that most of the below details were tested together but there are for sure some combinations I haven't tried or technique tweaks that weren't present in the systematic tests.

Beans
Wide variety: tried a couple 2-weeks-since-roasted beans, common grocery store beans like Lavazza Super Crema, less common grocery store beans from more local roasters (Barzula, Kicking Horse, Smile Tiger, Baden Coffee Company, Rufino, etc), beans with unknown roast date directly from supposedly-good coffee shops, etc. Some beans were super sour, definitely more sour than others. All were quite sour at best. I only tried a couple perfect-condition beans (2-3 weeks from roast date), but even those were sour. Most beans I used weren't the ideal freshness, but I've tried so many that I'm confident it's not the beans. I avoid anything that mentions bright or fruity in the tasting notes. Once, I went to an espresso machine store, tried espresso from a demo automatic machine (not sour at all), brought those exact beans home, and the express was sour. Same thing with my workplace's automatic machine. I did this again at an Italian-owned coffee shop, and same thing, the exact beans they used tasted sour on my machine.

Prep
My grinder is very clumpy. Most of my shots over the past year were prepped by grinding into a blind shaker, shaking to declump, transferring into portafilter (it would still be a bit clumpy), and "tamping" with a distribution tool with the depth set to what a tamper would compress the puck to. I know there's debate about using a leveller as a tamper but enough people have found it worked fine that I'm convinced it doesn't make a massive difference. Before, I used to use a normal tamper. Now I'm doing the WDT (homemade, cork + needles) after the blind shaker transfers grinds to the portafilter to get rid of all the clumps.

Water
Water in my area is very hard (500 ppm). My house has a water softener and I use Brita-filtered water for the espresso machine. Once, I experimented with a jug of bottled water from the grocery store which had ion concentrations (Mg, Ca, carbonate, etc) roughly in the same ballpark as some DIY water recipes I've seen on Home Barista. It didn't help, but that was a while ago and maybe I could revisit this variable to confirm.

Pressure
OPV was modded to 9 bar. Unsure if I noticed a significant difference before/after. Maybe I could buy a new OPV spring from Mr Shades set to 6 or 7 bar, if someone has tried that and it fixed their sour shots.

Temperature
This might be the biggest contributor to my problem, I'm guessing. I know temp stability is not good on this machine, so for the vast majority of my shots I temp surf by turning the steam switch on for 10 seconds just before pulling the shot. I think this has helped but I'm not sure. I've tried less than 10 seconds. Sometimes the machine is warmed up for 30min before the shot, sometimes it's not, since the warmup time didn't solve the problem. The portafilter is always left in the machine as it warms up so it's hot. I'm considering getting a PID to finally resolve whether temperature is the issue or not. I don't want to commit to that until I get more advice. The fact that there are plenty of Gaggia Classic owners who don't have a PID and aren't complaining about consistent unfixable sourness indicates that a PID might not be the solution.

Coffee In
I experimented with 14-18g, standard now is 16g. I thought more than that would add to sourness by leaving some coffee underextracted. Maybe I could go to 14g for a while to force the taste even more away from sourness (and towards bitterness but I don't care about that now) but that didn't work in my early tests.

Coffee Out
Standard is 36g. So 16g in, 36g out. Again, to push away from underextraction. I haven't really played with even more coffee out than this.

Grind size / Shot Time
I aim for >30s extraction time. Ideally I try to get 35s, again to push away from underextraction, but my consistency isn't too tight. I definitely notice more sourness if I pull a shorter shot, like 20s. I've ground fine enough to choke the machine, and I've tried shots with 1min extraction time, and those were still sour. My grinder model is definitely capable of good espresso but I did buy it used so maybe the grind distribution could be bad? I think that's a long shot.

Maintenance
I probably don't clean as much as I should, but I imagine that better cleaning would at best just make a slight improvement in taste, not the relatively massive difference I need to fix sourness. I descale with citric acid and backflush with Cafiza about once a month. Unless someone specifically found that more regular cleaning fixed a big sourness problem, I don't think this is a variable to adjust.

Channeling
For the majority of shots over the last year, I used one channeling prevention device (blind shaker) in addition to a leveller which replaced my tamper. Now I use two devices (blind shaker and WDT) just to be sure I get even distribution. I don't get squirting out of my bottomless portafilter, but I'll note again that the initial coffee grinds are very clumpy and I can only recognize channeling if it's obvious. Maybe I am getting channeling and just don't recognize it. The espresso flow is usually centered pretty well but away from the center there are usually small gaps or parts where there seems to be less flow. Sometimes the stream starts nicely but then grows into a foamy-looking "V"; in this case the rate of flow still seems pretty similar, so it's not like there's a massive channel forming. Maybe it's an indication of steam passing through the puck? Anyway, it doesn't happen all the time and the shots are still sour.

Sour/bitter confusion, or other taste problems
I am relatively new to espresso, but I'm not confusing bitter with sour. I've had espresso from three other machines (two automatic) that tasted very different from mine: bitter, so not fantastic, but no sourness at all. I've had espresso from five cafes (tested all in the same morning - not recommended!): two were super sour, two had a bit of sourness but were still drinkable, and one was super smooth and buttery and neither sour nor bitter. I can't recognize or classify tasting notes yet, but I can definitely tell if a shot is sour or not. Granted, I'm probably hyper-sensitive to sourness now that I've tasted so many bad sour shots.

I think that covers all the variables. I feel like my situation is unique as most other posts about sourness haven't considered all these variables. What could I be missing? Where is it likely that I have a blind spot, and think I've tested something fully but really haven't? Is there a variable that should be pushed to an even more extreme than I've already tried?

Ideally I would ask to meet up with someone experienced in my area who can help me in person, but that's not possible right now with Covid going on. I feel like I've done far more work in testing espresso variables than most people but still can't get good, or even decent, espresso, which is frustrating. So I'm finally asking for help. Thanks!

Edit: forgot to mention my shower screen is stock too, and when I run water through with no portafilter it doesn't look well-dispersed. I don't know if it's bad enough to cause problems, or if when a coffee puck is just underneath the water dispersion is better. But I don't really see how an upgraded shower screen would help just because it has clusters of holes.

I would check brew water temp first with an instant thermometer directly under dispersion screen with brew water running. next I would wonder about If you are actually getting the pressure you think you are.

But If you really like coffee and have the budget then upgrade the machine! If you are as passionate as you seem to be (as your detailed post seems to point out), you would be much happier with a better machine IMO.

You only live once!

Good luck to you

You don't need special baskets or to add on to any of the gear you currently are using.

From everything you've described it sounds like the machine isn't providing hot enough water. If you are handy and can PID it, you'll probably be much happier. But the way to narrow down the problem would be to make a simple, consistent filter brew of a few random coffees that you're finding sour, and see if they still taste predominantly sour. If not, then it's not the coffee.

If they did come out tasting rich, sweet, balanced, etc, it would push me to believe I'm not getting the proper temperature to the espresso puck.

It sounds like you're rather meticulous with the rest of the details, so I'd start there. And if you haven't, order a bag of fresh coffee that has seen second crack, preferably a blend, suited for traditional Italian style espresso.

I tested pressure with a pressure gauge screwed on to a portafilter with a little bit of a leak to mimic espresso flow. I know there's debate about whether to do that or not but truth is the portafilter threads didn't quite match the pressure gauge so I couldn't not have a bit of a leak =)

I don't have a thermometer for measuring temp, but I can get steamy water coming out if the steaming switch is flicked on for long enough. I haven't really confirmed if 10 seconds gets me steam our of the group head, I should do that to at least know that the initial temp is higher than what would cause sourness. I'd still have no way of knowing how fast that temp drops throughout the shot. Maybe I could also take more care to ensure that my portafilter is as hot as possible before pulling a shot.

I would be happy with a better machine, I know! I just don't want to spend that much yet, and I have a nagging doubt that even with an expensive machine, my skills or taste buds or expectations or whatever else is wrong will still mean I get espresso I don't like. I'm more willing to install a PID, but that would still cost a third as much as what my machine cost which is a lot of money to gamble on an uncertain improvement. Unless more people can't find a more likely solution.

Tyme wrote:I would be happy with a better machine, I know! I just don't want to spend that much yet, and I have a nagging doubt that even with an expensive machine, my skills or taste buds or expectations or whatever else is wrong will still mean I get espresso I don't like. I'm more willing to install a PID, but that would still cost a third as much as what my machine cost which is a lot of money to gamble on an uncertain improvement. Unless more people can't find a more likely solution.

I think you're better off trying to find either a vendor, cafe, or friend to test your palate on their equipment. If you can find someone you has a prosumer or entry level commercial machine, and can use your exact process in their environment, it would (my opinion) reveal whether it's the machine, your prep, your coffee, or your palate. I suspect it's a combo of machine and palate.

descaling once a month is probably more than necessary although it depends on your water.

What does it taste like when you pull just water through it? Are you sure you are doing a good job rinsing out that citric acid?

You can use a styrofoam cup (cut off short and pressed against the group head) and thermometer to try to gauge the brew temperature. What you measure will be a few degrees lower than the brew temp but should be in the ballpark.

I know it seems simplistic but it basically has to be temperature/grind/coffee.

Every post previous to mine has excellent advice.

Having someone experienced come over with their coffee and taking some of your coffee to play with on their equipment would be the next step. Ideally, someone with a Decent which could test your palate through a range of temperatures.

Auctor wrote:If you can find someone you has a prosumer or entry level commercial machine, and can use your exact process in their environment, it would (my opinion) reveal whether it's the machine, your prep, your coffee, or your palate.

Agreed. That, and having someone experienced use their process in my environment. About my palate, I've had enough other espresso to know that my palate isn't completely terrible. Granted, it's possible that I'm very sensitive towards acidity, but I have tasted shots (not mine) with no acidity.

Nate42 wrote: What does it taste like when you pull just water through it? Are you sure you are doing a good job rinsing out that citric acid?

I've never tasted the water, that's a good suggestion. Better citric acid rinsing wouldn't change things since my shots are still sour even 20 shots after the descaling.

Tyme wrote: About my palate, I've had enough other espresso to know that my palate isn't completely terrible. Granted, it's possible that I'm very sensitive towards acidity, but I have tasted shots (not mine) with no acidity.

No judgment on your palate! Everyone's flavor sweet spot is different. I recently had an award winning Panama Geisha that was $40 for 4 ounces and both my wife and I did not care for it.

The water test is also a good one. For instance, I use RPavlis, and while I think it might mute some brightness, the water is consistent and I can definitely taste variations across different coffees, so water as a variable remains constant and drinkable.

I don't have your machine, but I also have an entry level model (Bambino), and struggle with shots often being sour.

There are some things that my puck prep and my machine just can't handle well. Today I pulled a few shots, and the ones that I tried to make bitter came out sour. Two in a row I pulled with the same parameters. The first one was very sour. The puck also fell apart when I removed the portafilter and part was overly compacted. When I re-did the shot I was extra careful with my wdt and tamping. It was better, but still pretty bright. And the shot time was the same for both of them.

My belief if that I didn't get good, even extraction with these shots. I could keep practicing and see if I can make it better, but instead I backed off the dose by a gram because I've seen this before with my machine. Backing off the dose should have made the shot less bitter, but instead I got more bitterness. There was still acid, but this time it was balanced by the bitterness, a pretty good shot for this single origin coffee.

I've been trying to be make better shots, but at this point experiences like this suggest to me that I'm reaching the limits of my machine.