We’ve been experimenting the perfect amount of time for a cold brew, with different coffee beans. Latest one with a simple Lavazza Espresso, medium grind, 4:1 ratio and brewed for 20 hours was lacking flavour and had a distinct bitter aftertaste, sign of overextraction. The time before we brewed for 15 hours and it was great, flavorful and oily. The previous attempt was with a Kimbo espresso blend, which is a darker roast of this Lavazza one, so it came out stronger, bolder, but not more bitter. 15 hours seems to be the right amount of time for a cold brew with espresso blends normally to be found in supermarkets.…