I read lots of "stuff" about coffee preparation and had to try this...
I go down rabbit warrens...
When I read that spraying your puck with water makes a positive difference I was intrigued. The process is that you prepare your coffee puck as per normal, you finish by tamping and then you spray your tamped coffee with water... plain old water... just the stuff from the tap.
I have a water spray bottle next to my grinder as I use it to reduce static associated with single dose grinding. I end up spraying the puck about 15 times before putting it in the espresso machine. The two photos above demonstrate the difference in appearance of dry and wet pucks.
So the result this morning... I thought that my ristretto was slightly smoother and more rounded than usual. To me it wasn't a night and day difference. Helen felt that the difference was noteworthy and she enjoyed her flat white a lot. I think I'll be doing this a few more times in coming weeks and months. I'd really appreciate it if you would let me know your findings if you decide to try this method yourself. There's nothing better than adding a bit of breadth to an experiment to achieve more significant results!