title_body: Problems with Rancilio Silvia: How could I prevent getting too much or too sour espresso?
upvoted_answer: That's a pretty extreme contrast for a one-level difference.
  
  A couple things you could try:
  
  
  Use slightly less grounds if you're on level 23 - this will make your puck a bit easier to push water through.
  Weiss Distribution Technique - use a toothpick to break up any clumps you have in the grounds before tamping - try this on level 24, since you may have some channeling going on with the slightly coarser grounds.
  Pre-infuse your puck with grounds from level 23 - soaking them a bit early before starting the pull may help you to get a proper extraction. See this youtube video.