I just bought an espresso machine, Gaggia Classic.I tried making an espresso from pre-ground coffee with the pressurised filter (Crema Perfetta) that comes with the machine and I found the coffee was extracted quite fast. For example, within 10 seconds I already get 30 ml of espresso from 7 grams of pre-ground coffee. Despite having beautiful crema, the coffee tasted sour. Did I do anything wrong? The dosing I used was generally recommended for a single shot of espresso, but I used the 2-cup pressurised filter instead of the other smaller one that's said to be for PODs. Question 1: Any recommendations for getting a better shot of espresso from these things that I already have?
I also would like to try the non-pressurised filter selling online as it's claimed to produce better quality espresso. I have learned that this kind of filter is commercially used with commercial machines that generate the brewing pressure at 9 bars. But my Gaggia classic is 15 bars, based on the specification document. Question 2: Will this higher pressure result in faster extraction when I use a non-pressurised filter? I have learned that there are other factors that help slow down the extraction time such as tamping and grinding size, but Question 3: Will these factors be significant enough to overcome the 15 bars? I don't want to modify anything in the machine like adjusting the brew pressure of which the method is shown on the internet.Thank you for your comments and answers. I'm totally new to making espresso myself, but I really love espresso.