Shot by Greg K

Some bitterness at finish.

Looking at your shot data and tasting notes, the primary issue is grinding too fine, which is causing under-extraction despite the long shot time.

Key Evidence:

• Flow rate drops dramatically from 7.8 ml/s to 1.5 ml/s during pressure transition (19s→23s)
• Extremely slow flow throughout decline phase (0.8-1.1 ml/s vs 8.0 ml/s target)
• 58-second total time with significant channeling indicators
• Bitterness at finish suggests over-extraction of harsh compounds while under-extracting fruit acids

ONE Specific Recommendation:

Grind coarser by 15-20 clicks on your Zero Z1 (move from 190 to 205-210).

This will:

• Increase flow rate to hit closer to the 8.0 ml/s targets
• Reduce total shot time to 30-40 seconds
• Allow better water contact with all coffee particles
• Extract more bright fruit acids while reducing bitter over-extracted compounds

The extremely slow flow is preventing proper extraction of the fruity characteristics you want from this Kenyan coffee. Focus solely on grind size for your next shot - don’t change dose, ratio, or temperature yet.

Advice by Anthropic Claude