Brewed or Sat Too Long
Say what? You mean coffee doesn’t get better the longer it sits? No, Ma'am!
When you go to a restaurant and you feel like you are drinking acid that’s because the coffee was left in the grounds too long (French Press) or brewed coffee itself has been sitting for a long time. If the coffee is over 20 min old, we suggest you brew fresh (or ask your server for a fresh pot).
If this doesn't change the bitterness check out these other reasons for a sour cup: