I'm trying to get the perfect shot. Parameters: I have a Gaggia classic, a Vario grinder, a naked portafilter, and use aroma e Crema from Lavazza. I'm reaching an almost perfect shot ( 26 seconds of extraction for 2 ounces of espresso using 18 grams of freshly grinded coffee). My only problem is that I still have bitterness in my coffee.
My question for you is : How long should the coffee soak in the portafilter once I press the brew button before being extracted? Could that help with bitterness/ acidity?