Depending on your preheating method, you can vary the rate of the temperature going down. Shorter preheat leads to fast temperature ramp down, and vise versa. It will never go up though.

The flow is indirectly related to the pressure, and is the same as lever machine. Additionally on the Rossa PG, you can vary the preinfusion time and pressure ramp up rate - both will affect the flow rate, even with the same grind. Longer preinfusion or slower pressure ramp up will increase the flow rate. As a result, you need to grind finer to get the same flow rate. This behavior is suspected due to the fines migration.

Note to Mod: Please split this to a separate topic if you deem it necessary.

Hi Sam, with your pressure profiling device you could test your ideas on pressurized baskets in some depth. If you have a mypressi TWIST pressurized basket it will fit the Rossa. One thing you could do is grind for very fine espresso and sift your grinds with a 150-200 micron sieve. That should give you a fairly unimodal grind peaking at around maybe 300 microns. Throw that into the basket and see what you get when extracting under different pressures.

I suspect you'll get similar results all around: inability to do pre-infusion (which probably doesn't matter), relatively sweet and long shots with a nice airy fake froth. Probably really nice Lungo type shots, regardless of the pressure. But then again since you can vary from 1-20 bars, keeping other variables constant, it would be interesting to see what differences occur at various extremes. The coffee will always be forced through the pinhole, thus creating the same type of airy coffee, but with different pressures maybe the texture and the flow might change a lot.

Sounds like an interesting thing to play around with. You'll probably never get a conventional espresso shot no matter what you do but you might get some tasty beverages. But most interesting I think is learning more about to what extent pressure affects extraction.

I dig this thought. Might have to play around with it.

I wouldn't mind trying this, just to see how it effects taste and extraction rate. I would tend to think it would either simply slow down the shot or make it taste horrible for some reason.