bas wrote:...do I understand well that by flushing less and waiting shorter the temperature profile is flatter and with a longer rebound time there's more "hump"...are there general rules, e.g. a SO favours a flat profile and a blend a humped one...or a lighter roast versus darker?
That could be a general rule, but more likely it is a point of debate, and some research. Not bad, fourth post and you have located one of the central bones we like to chew.
The first call was that just about any blend would benefit from a flat profile. The number of great shots I get out of the La Peppina, which is temp stable as you can ask for, there could be something to be said for this argument. That same flat profile also pulls some great SO shots.
On the other hand the S27 can give me either 'u' or 'n' shaped temp profiles on a shot, depending on the flush and how long the machine has been idle, but hardly ever flat ones. It's just the nature of the beast.
I find with the larger basket and the faster pressure ramp that I grind a bit coarser and tamp a bit harder than with the spring lever. The coffee that I get while different can be just as good if I can temp surf the same average temperature area as I am pulling from the La Peppina.
To make this long story not so much short, but to get it to go away. The take home is if the average temp of your shot is near the 'sweet spot' for that roast/blend/bean you may like the flat temp taste, or you may find that a bit of wiggle room gives you a more interesting taste.
Have fun messing with the rules Bas.