Gaggia Evolution, 2 issues

[Mhippo]

I have a Gaggia Evolution machine, and just recently finished an upgrade of the OPV to the Gaggia Classis (adjustable) OPV. I still have 2 issues, which may or may not be related.

1. I dialled the brew pressure down to 9 Bar, and still am not able to get good crema. I even tried using a pod, to rule out tamping issues, and the problem is still there, I get a very thin crema which dissipates completely within seconds. The extraction is also pretty fast, but I thought 9 Bar was the correct brewing pressure.

2. The group valve gets stuck ~once a week, and I need to take the grouphead apart, remove and reinstall the group valve, and it works again. Also, when it works at all, the group valve lets water through even without the pump operating. Do I need to replace it, or is there some way to repair?

 

[shadow745]

8-9 bar range is acceptable. Really depends on your taste preference, etc. How exactly are you testing this?

Thin crema is usually due to stale coffee, but other gremlins may be at play as well. Super fresh coffee can often give tons of crema, which dissipates very quickly leaving a thin/watery shot when all variables are dialed in well, just that the coffee needs several days to rest.

Fast extractions are usually caused by stale coffee, grind that is too coarse, dose that is too low, etc. Using a pod to test is nothing more than a waste of time. Often beginners will use old coffee to dial equipment in, which is not a good approach as stale coffee will just magnify existing issues.

If the group valve is sticking/leaking you should look for mineral deposits/coffee oils that could be causing this. Or possibly a weakened spring. How old is this machine? May not be a bad idea to replace these parts if the machine has a fair amount of age/wear on it.

 

[shadow745]

Just found this video that may be quite helpful for you on the group valve...

Gaggia Espresso Group Valve Cleaning - YouTube

 

[Mhippo]

8-9 bar range is acceptable. Really depends on your taste preference, etc. How exactly are you testing this?

Thin crema is usually due to stale coffee, but other gremlins may be at play as well. Super fresh coffee can often give tons of crema, which dissipates very quickly leaving a thin/watery shot when all variables are dialed in well, just that the coffee needs several days to rest..
Fast extractions are usually caused by stale coffee, grind that is too coarse, dose that is too low, etc. Using a pod to test is nothing more than a waste of time. Often beginners will use old coffee to dial equipment in, which is not a good approach as stale coffee will just magnify existing issues.

I have used ecerything from day old to week old coffee (same roast, ground fresh for each cup). The best I got was with a grind that choked the machine for 15-20 seconds before it came out. The pods are supposed to be roasted, ground and tamped to perfection, so I thought a pod would rule out most of the gremlins.

Also, the shots aren't watery. They're nice strong shots. The only issue is crema.

If the group valve is sticking/leaking you should look for mineral deposits/coffee oils that could be causing this. Or possibly a weakened spring. How old is this machine? May not be a bad idea to replace these parts if the machine has a fair amount of age/wear on it.

The last thing I did, after finishing the upgrade, was a full descaling. I bought this machine a year ago, and I got it as a floor model, meaning it was used in the store for who knows how long... The spring doesn't feel weak, I was wondering if the ball was maybe getting stuck, which would explain why it gets stuck both open and closed.

Just found this video that may be quite helpful for you on the group valve...

Gaggia Espresso Group Valve Cleaning - YouTube

I watched that video first, wasn't any help. But thanks for finding it for me.

 

[shadow745]

To each his own, but a pod is useless for espresso IMBHO. I challenge anybody to prove otherwise...

Pods ground/tamped to perfection? How does that roaster determine that as every single machine has a slightly different sweet spot. Never have seen a tamped pod either.

Most fresh roasted coffees for espresso are going to need 3-7 days to mature. What coffee(s) (origin, wash/processed method, Arabica vs. Robusta, etc) have you used? I ask because crema production can be influenced by many factors beyond just being fresh.

Also, how are you storing the coffee? Beans exposed to air even half a day (left in hopper) can be a night/day difference in terms of thick/warm honey extractions vs. thin crema, etc.

How much is your average dose? How are you testing brew pressure?

Make sure the ball part of the valve is perfectly round as any imperfections could cause it to stick.

 

[Mhippo]

To each his own, but a pod is useless for espresso IMBHO. I challenge anybody to prove otherwise...

Pods ground/tamped to perfection? How does that roaster determine that as every single machine has a slightly different sweet spot. Never have seen a tamped pod either.

The pod is compressed. I thought it was for tamping purposes...

Most fresh roasted coffees for espresso are going to need 3-7 days to mature. What coffee(s) (origin, wash/processed method, Arabica vs. Robusta, etc) have you used? I ask because crema production can be influenced by many factors beyond just being fresh.

Mostly I've been working with my wife's Decaf, waiting for my blend to equalize before I roast it.

Also, how are you storing the coffee? Beans exposed to air even half a day (left in hopper) can be a night/day difference in terms of thick/warm honey extractions vs. thin crema, etc.

How much is your average dose? How are you testing brew pressure?

I store it in the hopper. Is there a better way? I measure the pressure with a PF mounted analog pressure clock

Make sure the ball part of the valve is perfectly round as any imperfections could cause it to stick.

I'll check next time I open it up.

 

[shadow745]

Decaf by nature of the process won't produce much crema based on my experience. It will if quite fresh, but fades rapidly. The window of opportunity is much smaller than similar non-decaf versions. Since you roast what green coffees are you choosing? As you may know some coffees are just better suited for the pressure achieved with espresso in terms of taste, body and crema production. Pay attention to how the coffees are processed in terms of wet vs. dry, etc.

I would only store in the hopper if I were trying to degas a coffee overnight. My current method of storage is the most consistent for me after many different forms of tinkering. When I order coffee it is roasted/shipped to order locally. I let it age 5 days in the bag from the actual roast date, then weigh/vacuum seal in glass Mason jars. Then it is stored at -30 in our deep freezer. For each brew session I weigh out what I want from a frozen jar and let it come up to room temperature while the machine is warming up. Then I dump the coffee in the grinder and use. In the past I would thaw out a jar, which is 156 grams which gives me 9 doubles. I found the consistency changing a bit much even within the 2-3 day period I would use this amount. This may be a bit much for some, but it works well for me as each double tastes the same jar to jar. Deep freezing doesn't eliminate the staling process, but does slow it down a lot. FWIW I have vacuum packed/frozen decaf coffees and used them up to 7-8 weeks later and still perform as if they were 3-4 days old. Key to deep freezing is doing it just as a particular coffee reaches it's peak so each jar is just about perfect when opened.

Most of the time those dialing in the OPV with a portafilter mounted gauge usually tune it to around 9.5 bars to factor in plumbing, static pressure, etc.

 

[Mhippo]

My blend is Colombian/Brazilian, Ethiopian, Indian Arabica and Indian Robusta. I'm currently using up my stock of Colombian, because I read that it's not very good for crema, and switchung in Brazilian instead. The Robusta and the Brazilian I buy from a coffee store, where I can ask about the processing method, but the others I buy in the local open air market from stores catering to the Ethiopian community, where they can tell me the origin, but no more than that.

I don't have a deep freezer, and read that putting coffee in a regular freezer damages it, any other suggestions? Also, I roast it myself, so it's not in an airtight package, so how long do I age it before storage?