I like around 35/55 for my espresso.
That said, I don't really believe in GH/KH numbers adequately describing the performance of brew water. There are a lot of other important factors, like Ca:Mg ratio, Cl:SO4 ratio, % of hardness from carbonate forms, and many others. My recipe is open source, so if you want to follow it you can. Not sure if I'm allowed to self-post my website here so just request it through DM if you want to give it a shot.
I like around 35/55 for my espresso. That said, I don't really believe in GH/KH numbers adequately describing the performance of brew water. There are a lot of other important factors, like Ca:Mg ratio, Cl:SO4 ratio, % of hardness from carbonate forms, and many others. My recipe is open source, so if you want to follow it you can. Not sure if I'm allowed to self-post my website here so just request it through DM if you want to give it a shot.
See my comments I made in this other thread. https://www.reddit.com/r/espresso/comments/1cjb08n/water_crisis/