As the puck is wetted eventually the headspace fills, saturation begins to occur and THEN pressure begins to rise. A "Bloom" or hold phase would maintain (or create a slow decline) from that low (1-3 bar) pressure while adding no water. This has to be done while maintaining pressurization or you run the risk of unseating the puck when the pressure ramps up.

mgrayson wrote:Serious question: If puck blooming is vital, has anyone tried simply pouring hot water on the puck BEFORE locking it into the machine? Pressure is supposed to be minimal, right?

You'd get to use a gooseneck kettle AND an espresso machine!

I've always wondered about this technique of pre-infusion - why not just wet the puck beforehand as you mention? On my Oscar, i was thinking of just turning on the pump for a few seconds then turning it off but then this would turn on the solenoid and dump "bloomed" liquid to the drain tray.

Pre-infusion is when the lever is down (or up). Infusion is when the lever is raised (or lowered).

mgrayson wrote:Serious question: If puck blooming is vital, has anyone tried simply pouring hot water on the puck BEFORE locking it into the machine? Pressure is supposed to be minimal, right?

You'd get to use a gooseneck kettle AND an espresso machine!

People have sprayed water on the puck before inserting the portafilter into the group. A gram or so IIRC. SBPWT - Spray Bottle Pre-Wetting Technique http://www.youtube.com/watch?v=nXrQ7T5YD94

baldheadracing wrote:Pre-infusion is when the lever is down (or up). Infusion is when the lever is raised (or lowered).


People have sprayed water on the puck before inserting the portafilter into the group. A gram or so IIRC. video

Does blooming require hot water? In pour-over, it is usually brew temperature (or hotter, if I recall some Hoffmann video correctly).

mgrayson wrote:Serious question: If puck blooming is vital, has anyone tried simply pouring hot water on the puck BEFORE locking it into the machine?

Not exactly, but kind of...
I've moved the switch on my GS3 MP slightly, which allows for a kind of line pressure PI (I guess pre-wetting, really) before the pump engages. Since the exhaust port is basically wide open at this early paddle position, water just dribbles on top of the puck without any real pressure build, with the group gauge pinned at zero throughout.
I've stopped the shot at 5,10 and 20 seconds of this "PI" then cut into the puck to measure the water penetration. Even at 20 seconds the water is barely a third of the way into the puck. At 5 and 10 seconds only the top quarter was saturated.
By oversaturating the top of the puck long before the bottom sees any water at all, this technique didn't seem to be going in a helpful direction - at least as far as taste goes - so I didn't bother pushing longer. It can still be a useful tool though, as shots were better behaved generally. With a difficult coffee I can pretty much eliminate channeling with a 5s pre-wet before slamming it with the full 8 or 9 bars, though I should note that I'd generally be using some sort of lever profile with these.
Pre-wetting before a 3bar PI just muddies flavours IME.

mgrayson wrote:Does blooming require hot water? In pour-over, it is usually brew temperature (or hotter, if I recall some Hoffmann video correctly).

I would guess that it doesn't matter for the spray bottle technique as the amount of water is small compared to the mass of the coffee+portafilter basket. (I don't use the method.)

Regardless, whatever water hits the coffee first is going to be cooled immediately by the coffee+basket so whatever we want to call the initial phase will always happen at a lower temperature than the average brew temperature.

(Blooming in pourover is a different rabbit hole.)

Well, except that the trend with a temperature-agile machine is to boost the initial fill temperature and decline during the high-flow extraction, sometimes significantly.

... just like a typical commercial lever group machine. J/k

Seriously, one of the things that I would love to try is to replicate Rancilio's research that seems to show an increasing temperature profile might be desirable - at least with whatever coffee that they used. Summary (2019): https://www.beanscenemag.com.au/brew-wa ... xtraction/

mgrayson wrote:Serious question: If puck blooming is vital, has anyone tried simply pouring hot water on the puck BEFORE locking it into the machine?

I do this. Have for a few years. I have a 1982 la pavoni pub which is hx commercial machine and can't preinfuse. I read on the decent forum that the decent staff compete in shot pulling and someone sprayed the puck to pre-wet it and got more even pulls.

So I started using my rtd sprayer. It worked. I know it's cold but just enought to stop water hitting a completely dry puck gets a more even pour (for me...YMMV)

I also use a puck screen. Found way more even pours (bottomless portafilter) with it.

Over the last six months been trialling something else with some success. After flushing excess hot water, I let the hot water from the group head fall into the puck as I'm attaching the portafilter, then stop the pour and wait, then continue about 15-20 secs later. This doesn't break up the puck as the water lands with little force. This is working well for me. I've tried 'pulsing' to preinfuse but with little success and this does sometimes stir up the puck if no puckscreen is used.

on their website it doesn't say summer 2022 anymore, it says fall 2022