My Experiment in Variable Brew Pressure via Steam Wand for Single Boiler Espresso Machines

[TimEggers]

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).

[bdbayer]

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

[another_jim]

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.

[TimEggers]

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!

[hbuchtel]

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

[AndyS]

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!

[TimEggers]

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!

[CraigA]

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 http://www.coffeegeek.com/forums/...ines/283895#283895

Cheers!
Craig.

[bdbayer]

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

[TimEggers]

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!

[hbuchtel]

Tim, can you swivel your steam wand around so it shoots the water back into the reservoir? Mine doesn't reach unfortunately...

Henry

[TimEggers]

Tim, can you swivel your steam wand around so it shoots the water back into the reservoir? Mine doesn't reach unfortunately...

Henry

No...

But I tried!

[Kaffee Bitte]

This sounds somewhat similar to what one of the elektra microcasa a leva owners was doing to control the shot temperature for coffees that are best at the lower end of the temp spectrum. I can't remember what post it was, but I believe it was Trish that wrote it. Anyway I plan on trying something similar to this when my pavoni arrives to see if it can be adapted for a lever. I believe that Trish was using the boiler pressure gauge by running the steam to bring the pressure down to around .4 bar. Once it was there she closed the steam off and pulled the shot. Interesting idea. We'll see about the adaptation. Thanks a ton Tim for another really wild thought.
Lynn

[hbuchtel]

Anybody else finding this useful?

I like it most for the simple reason that my machine doesn't have an OPV and too fine of a grind can get... messy... but with one hand on the steam valve I've turned several potential explosions into melted coffee butter ristrettos.

It's also nice to follow the Pressure Profiling thread knowing I at least have the potential to imitate Greg's findings!

I'm going shopping for a pressure gauge next week and also want to put another steam wand upstream from the boiler...

Henry

[oofnik]

Tim, great idea. I actually started doing exactly the same thing for a little while with my crazy contraption of an espresso machine, which has a very similar design. I opened the steam valve a little for a few seconds and watched the pressure ramp up on the gauge until I saw the espresso and then I closed it off. I didn't really get a chance to notice a definite improvement but I think the shots were slightly smoother in general. The only issue with this is that more cold water has to be pumped into the boiler which might have an impact on the temperature stability. Great idea though and thanks for sharing.

[cannonfodder]

Good Lord! What did that Frankenpresso machine start life as?

[oofnik]

Haha. It used to be a La Pavoni Club Combo, similar to the Gaggia machines. I made my PF naked, added a PID, completely revamped the plumbing to include a pressure gauge and a relief valve, uh.. and it didn't exactly fit under the hood when I was done so I left it off. It served me well until I got my Wega working and now it's just sitting in the garage.
It started life as this:

[hbuchtel]

I put a pressure gauge and a valve on the cold water side of the boiler.

This was the second shot from this set up, I tried to keep it at 9 bar (as shown on the gauge) then let it off towards the end.

12 grams of ~50/50 Brazil + Mandheling

The espresso was full of flavors I've never tasted before, really an experience! The aftertaste was not so nice, however, which could be because of my continuing distribution problems.

[oofnik]

Now that's kinda cool. I like it! I see that you too enjoy the challenge of maximizing the capability of a machine regardless of the amount of effort required to do so. It's analogous to porting the heads, replacing the pistons, camshaft, and headers, installing a supercharger, reprogramming the ECU, upgrading the exhaust, adding an intercooler, a hood scoop and a nitrous oxide injection kit to a 1.6L Honda Civic LX.

[hbuchtel]

to a 1.6L Honda Civic LX.

sigh... it's true!

I just pulled a great shot with 15g and ~30sec extraction... wow! I've never managed to do that before!

Henry