I just found this old thread about pressure profiling started by Nicholas. It's a fantastic read and it really helped explain things I was experiencing with the EsFg.

With the EsFg there's really no way to avoid a long pre-infusion at 0 bar, or pre-brew, using the terminology of the thread. This means for the first 10-20 seconds of the shot, there is water flow but no pressure (ie 0 bar) while we fill the cylinder with water from a kettle. I personally can't do this faster than about 10 seconds, typically it's slower at 15s, so by the EsFg's nature we need to adjust to a much finer grind (I know, I know this is old news). This is called the first "1/3" of the shot, which in the thread, is said to be the most critical part to determining how the shot will turn out.

What I think is really interesting is the dynamics of the last "2/3" of the shot. This is where the piston in engaged into the cylinder and we can now begin to add pressure. During the next "1/3" of the shot, immediately after pre-brew (ie after we're done filling the cylinder and engage the piston), we can pressure profile in various ways. Sometimes I continue the long pre-infusion at 2 bar before I ramp up to 9,10, or 11 bar; sometimes I just ramp up to max pressure immediately.

Now, how the ramp up to max pressure is done (and what the max pressure is) effects the flow of the shot drastically.

1. If you drag out the pre-infusion longer and casually build up to max pressure, then the flow of the shot will be very quick.
2. If, instead, you ramp up to max pressure quickly, then the flow of the shot will be very slow, near choke.

From what people have posted, it seems many stick to the "standard profile": quick ramp up to 9 bar of pressure then decline to 6 bar over approximately 20-40 seconds (plus an additional pre-infusion at 0-2 bar anywhere in the 10-40 second range). The "long pre-infusion" where not only is the period of pressure of 2 bar dragged out for 10-20 seconds but the pressure climb up to 8-9 bar is slow.

Here are some other recipes I've tried.

LMPP "Low Max Pressure Profile": pre-brew for 15 sec, pre-infuse at 2 bar for 10 sec, slowly increase pressure to 6 bar over 5 seconds, hold at 6 bar for 10 seconds, decline to 4 bar over additional 10-15 seconds. Complete shot length is 45-50 seconds with a relatively quick flow. I like this recipe for a medium-light roast espresso/brew roast in ~8 oz of cold milk and ice cubes.

VLCEP "Very long cold espresso profile": this one is nutty (won't say who suggested it to me ). I've only tried it a few times with cheapo coffee so I'll withhold taste descriptions. Basically grind a tad finer than usual for the EsPg (don't go overboard, first attempt choked the set-up and I couldn't pull the shot even at over 11 bar), lock in the room temperature basket and lock ring into the room temperature body. Pour cold water into the cylinder and wait 20 minutes. Put in piston, pull shot as normal. My attempts have been directly into cold milk just to try it.

Any other interesting profiles you've tried?

beer&mathematics wrote: Any other interesting profiles you've tried?

Yep, pretty much all of them listed here!

samuellaw178 wrote:I recently have come to like the 0.5bar-4bar-9bar-declining profile as described by Dominick in Pressure Profiling Techniques for Spring Levers. Seems to give a better body and very delicious looking shots every time.

Ok, I actually had the time to do my Scace test this evening:

I preheated the Forge using a Fino kettle at boiling on a stove top.

I found that the max temperature I achieved with a prewarmed Scace device (btw, pulling a hot scace device from portafilter is not fun)
was 200F (93.3C) when the temp strip showed 194F(90C) and I poured boiling water into it immediately, pretty much validating Sam's JBWeld-device readings.

Curiously enough when I let it cool down to where the strip said 176F (80C) and then poured in the boiling water I got a max scace temp of 190F (88 C). I would have expected it to be lower than that.

beer&mathematics wrote: VLCEP "Very long cold espresso profile": this one is nutty (won't say who suggested it to me ). I've only tried it a few times with cheapo coffee so I'll withhold taste descriptions. Basically grind a tad finer than usual for the EsPg (don't go overboard, first attempt choked the set-up and I couldn't pull the shot even at over 11 bar), lock in the room temperature basket and lock ring into the room temperature body. Pour cold water into the cylinder and wait 20 minutes. Put in piston, pull shot as normal. My attempts have been directly into cold milk just to try it.

This is new to me. Will try that.

dominico wrote:I found that the max temperature I achieved with a prewarmed Scace device (btw, pulling a hot scace device from portafilter is not fun)
was 200F (93.3C) when the temp strip showed 194F(90C) and I poured boiling water into it immediately, pretty much validating Sam's JBWeld-device readings.

Curiously enough when I let it cool down to where the strip said 176F (80C) and then poured in the boiling water I got a max scace temp of 190F (88 C). I would have expected it to be lower than that.

Thanks Dominick! Much appreciated for the hard work. Yes, it's definitely not easy especially if your spring is tight!

Good to see some number agreement though mine is a tiny bit lower (by 1C or so but it's not that different in this context). The way it turned out now is quite interesting. This means you can just steam-preheat as hard as you want and it'll be in the brew temp without worrying about overheating - no PID kettle needed! But of course that also means it imposes a ceiling temp - you can't brew at 94-95C+ if that's called for.

I might have missed this point when I read the temperature experiments but what is the heat up process for the EsFg that you followed Dominic?

Was it room temp? Electric kettle steam warm? Stovetop kettle steam warm?

I'd like to know since I've noticed a few things lately (again I'm so sorry if this is old news to everyone!!). With the steam warm-up on the Bonavita Electric PID kettle set at max 212 dF, the EsFg warms up but the top of the piston never gets hot enough to burn your hand.

On the other hand, if I use the base of my Moka Pot to warm up the EsFg on the stove (thanks Dominic for the tip in one of your old posts), it gets absurdly hot! To the point that handling the EsFg burns your hand even through the tape (I have the V1).

Ok, carry on. I'll try to stop posting such obvious things

I recommend focusing on how fast the piston is moving instead of how much pressure is being applied. The former has the larger and more direct effect on taste. But unfortunately there is no gauge for it.

dominico wrote:Yep, pretty much all of them listed here!

Woohoo! More reading and experimenting! Thanks

jonr wrote:I recommend focusing on how fast the piston is moving instead of how much pressure is being applied. The former has the larger and more direct effect on taste.

Interesting. Care to elaborate? I mean, to move the piston faster you need more force, hence pressure, and moving the piston slower means less force, hence pressure. Am I missing something?

beer&mathematics wrote: Was it room temp? Electric kettle steam warm? Stovetop kettle steam warm?

I've edited my post to list my warmup, I used a stovetop fino kettle at boiling for this. I moved on from the moka pot because I found it cumbersome to pick up and pour the boiling water in once preheated.

Maybe on your Bonavita the steam is able to escape around the seal of the Forge base and doesn't go up the tube?

Of course flow and pressure are related, but the exact relationship is unreliable. And after much taste research, I'm convinced that of the two, flow rates are the most important - controlling pressures to achieve the proper flow rates is a convenient but not so accurate approximation.

I see what you mean now. You are talking about the flow of the espresso stream (I was thinking of the speed of the piston). This makes sense, and is quite simple model. It's been repeated in many threads (and it IS good advise!), and maybe I'll eventually stop the experimenting and settle on focusing on flow only, but I'll admit it's a bit anti-climatic for the tinkerer in me.