I bought an older Rancilio Silvia machine and try to adjust the grind of my CM90 grinder.

On grinding level 24 I get with 15g powder after 25 seconds 73g espresso in two cups which is way too much (it should be 35-40g).

On grinding level 23 the machine is able to get any espresso if I tamper normal. If I barley tamper, I get 27g Espresso after 25 seconds, but it tastes horrible sour.

I do temperature surfing and wait 0 to 20 seconds after the heating phase before I start the machine. I tried different beans which are 1 to 3 month old.

Any idea what might be the problem?


That's a pretty extreme contrast for a one-level difference.

A couple things you could try:

  1. Use slightly less grounds if you're on level 23 - this will make your puck a bit easier to push water through.
  2. 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.
  3. 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.

Check the feel of the grind on level 24, if it's consistency is similar to fine salt then check the tamp pressure. The age and quality of the beans also is an issue. If you have a gauge check the bar pressure to ensure it is 9 bars in brew mode. I have a Rancilio Silva but I grind on a Rocky Doserless. I check bar pressure every time my brew is less than perfect, a little ocd.

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