Ok sorry for long title, but you get the idea...

I have been long trying to understand the importance and the possible improvement I could realize with different brewing pressures. My humble Gaggia Coffee does NOT have and adjustable OPV and modding my machine seemed a little risky to me.

So an idea struck me (just like when the 2-liter bottle thing went off in my head) what if I open the steam valve during brewing? I thought no it couldn't work; the resistance of the coffee would just force all the water out the steam valve. So I tried it...

It seems to work great! I pulled a shot of some super fresh (4-hour old) Sumatra because that's the only beans that I have. I was surprised to see the level of apparent adjustability I really had. I feared it might be an all or nothing adjustment. Actually I saw a reasonable slow and variable flow rate. I could run with the valve shut to put full pressure to the puck, or open the valve to ramp clear down to no flow at all. I was surprised at the range of the adjustment too, nearly a full half turn of the dial!

The ideal application of this would be I suppose to put a pressure gage on this thing to see where I need to have the steam valve set to in order to get the desired pressure at the puck. This it would seem should work.

Another application of this would be an initial low-pressure delivery of the water to the puck to pre-infuse, then a ramp up to the desired brew pressure.

I believe that if one has a pressure gage they could easily mark where the knob has to be for different pressures.

So there you have it a variable, adjustable brew pressure system that in no way modifies the machine. Best of all the steaming capability isn't affected. Shut the valve, turn the machine to steam mode, wait for steam temp then steam. Nothing to remove or bypass to steam.

There has to be a catch to this whole thing because it is simply just too easy. What am I missing?

The shots I made were noticeable different. Less bitter, smoother body and nice improved sweetness. I have more experimentation to do, but so far this seems like it could be a very viable method.

I made a video to demonstrate this in practice. It's a terrible shot, but I wanted to illustrate and document the affects of the process. If you watch close (and listen) you can see and hear when I open the steam valve. The flow will accelerate and recede as I turn the dial (I was turning it kind of fast).

«missing video»

I have wondered about this for a short while. When I brought up the possibility in the thread Getting a good shot from Silvia? it didn't seem to ring any bells with anyone. The conversation went to the standard temp surfing on the Silvia instead of consideration of the wand changing the pressure. (Not real sure how to insert those links)

I sold my Silvia in favor of the Vibiemme Domobar Super, so my experimentation is done. But I really think you're on the right track here.

Barry Bayer

Very clever indeed!

For 9 bar, you should see around 3 only ounces total in 25 seconds, cup and drain combined. For 6 bar (lever territory), you're looking for 4.5 ounces combined. These are rough numbers based on the Ulka pump curve.

Barry,

Yes I don't recall this being discussed and I humbly apologize to anyone who has done this and shared it. I have not seen such information.

Jim,

Thank you! To hear remarks like that from you means a lot. I still need to do some more experimentation. I appreciate your volume quotes (I must admit I didn't consider being able to replicate a lever-like pull). The sheer flexibility this method can offer looks to be another pro to it's use.

One thing is for sure I do see a great deal of change in the shot quality.

I also really like the variability of it and it's sheer simplicity in implementation. Call it a cheat if you will, I sure like!

That's a great idea Tim, thanks for posting it! (and kudos to anybody else who thought of it )

Ah, now my machine has an adjustable OPV! That was easy

Henry

Tim:

Great idea. One of those things where I said, "why didn't I think of that!"

Especially considering how youthful you look in your avatar photo, I'm impressed!

Henry,

Yeah it's really simple. I'm surprised it hasn't been mentioned before (then again maybe I missed it). In fairness, Barry did mention it another thread but no one else (myself included) really picked up on it. And I don't recall others before him touching on it. For it being so simple I'd of thought it would have been more widely used, again perhaps it is and it just isn't talked about.

Andy,

LOL! Yeah, I guess espresso is my fountain of youth!

Hi Tim,

I didn't mention it this post of mine in the thread or my other posts there, but I did indeed try this out https://www.coffeegeek.com/forums/espre ... 895#283895

Cheers!
Craig.

Hey Tim,

My comments had nothing to do with credit, forgive me if it sounded that way. I read many of your posts and you definitely are one of those who is thinking things through. This thread is just proof of how much thought you are putting in to better quality shots.

You keep up the good work.

Barry Bayer

Oh no Barry not at all! I just thought I'd share some things that I try hoping that maybe others will chime in with what they have tried and even better that they find that works!

I agree it's about better espresso. I have a long ways to go and I'm no espresso scientist but this is a hobby I greatly enjoy and it's a real pleasure sharing my discoveries and progress with my friends on HB!