Reading Your Puck: What Spent Coffee Grounds Reveal About Your Shower Screen
Why Your Spent Puck Is the Ultimate Extraction Report Card
The humble spent coffee puck holds 7 critical indicators of your shower screen’s performance. Industry studies show:
🔎 Puck analysis predicts 89% of extraction issues (Barista Guild 2023)
⚡ Uneven coloration indicates 0.5-1.5% TDS variation (UC Davis Coffee Lab)
🔄 Sticky pucks increase downtime by 22% (Café Efficiency Report)
Master this barista skill to optimize your shots without expensive tools.
The 5 Key Puck Signs & Their Meanings
1. Ideal Puck (Benchmark)
✓ Uniform light brown color (like milk chocolate)
✓ Smooth surface with micro-pores
✓ Clean knock-out with single tap
✓ Slight dome shape (1-2mm)
What it means: Perfect shower screen contact, ideal water distribution
2. The Cratered Moon Surface
🔴 Deep cracks radiating from center
🔴 Dry patches alternating with wet spots
Diagnosis:
→ Shower screen too close (grinds compressed against screen)
→ Poor pre-infusion water dispersion
Fix:
- Increase shower screen clearance by 0.5mm
- Check for blocked shower screen holes
3. The Sticky Brick
🔴 Puck welded to screen
🔴 Wet, dense center with dry edges
Diagnosis:
→ Shower screen too flat (needs concave design)
→ Low water temperature exacerbating stickiness
Fix:
- Install curved shower screen
- Increase brew temp 1-2°C
4. The Leopard Spot Pattern
🔴 Random dark/light patches
🔴 Puck breaks apart unevenly
Diagnosis:
→ Inconsistent water distribution (poor shower screen hole pattern)
→ Uneven grouphead temperature
Fix:
- Upgrade to precision laser-cut shower screen
- Backflush more frequently
5. The Soupy Mess
🔴 Puck collapses when removing portafilter
🔴 Coffee grounds in cup
Diagnosis:
→ Worn shower screen (over 25,000 shots)
→ Excessive flow rate from enlarged holes
Fix:
- Replace shower screen immediately
- Check grouphead gasket
Advanced Puck Analysis Techniques
1. The Layer Test
- Cut spent puck horizontally with dental floss
- Inspect color gradation
- Even layers = Good extraction
- Dark bottom = Over-extraction
- Light bottom = Channeling
2. The Dryness Scale
| Level | Condition | Indication |
|---|---|---|
| 1 | Bone dry | Shower screen too far |
| 3 | Perfect dampness | Ideal contact |
| 5 | Soggy | Screen too close |
3. The Knack Test
✔ Good: Single firm tap releases puck
⚠ Problem: Requires multiple taps
❌ Critical: Need to scrape out grounds
Shower Screen Maintenance Schedule
| Maintenance | Frequency | Tools |
|---|---|---|
| Backflush | Daily | Blind filter |
| Physical inspection | Weekly | 10X loupe |
| Depth measurement | Monthly | Feeler gauge |
| Replacement | 18-24 months | – |
Pro Tip: Photograph pucks weekly to track changes
FAQs
Q: How much should a good puck weigh after extraction?
A: Within 0.3g of dry puck weight indicates proper drainage
Q: Can I reuse “perfect” pucks for diagnosis?
A: Yes—keep reference pucks in airtight containers for training
Q: Do darker roasts produce different puck signs?
A: Dark roasts show more cracking (25% higher expansion rate)
