Why does my espresso taste bitter, and how can I fix it?

A bitter taste indicates over-extraction, which can be caused by grinds that are too fine, too much tamp force, or scale build-up in the machine. Try using a coarser grind, tamping more lightly, or running the descaling program as outlined on pages 20–21. Using the steam function just before pouring an espresso can also cause a burnt taste — wait until the READY light is fully illuminated before pouring. (Page 22-23)