#tea-grading

I’ve spent the last three weeks brewing 5 g of Tieguanyin in three different pots—copper, stainless‑steel, and porcelain—while keeping leaf grade (Grade A vs. Grade B) constant. The results make the whole grading system look like a marketing gimmick.

Key observations:

• Temperature retention: Copper’s thermal conductivity (≈400 W/m·K) keeps the water at 93 °C for 40 s longer than porcelain (≈2 W/m·K). That small window boosts extraction of the same volatile compounds.
• Ion exchange: Copper releases trace Cu²⁺ ions, which bind with sulfur-containing compounds in the tea, reducing the sharp “roasted” note that often masks the delicate floral profile.
• Volatile profile: GC‑MS analysis shows a 32 % higher concentration of linalool and 18 % higher terpinen‑4‑ol in the copper brew versus porcelain, while the polyphenol (catechin) content varied < 3 % across all vessels.
• Leaf grading: A side experiment measured catechins, caffeine, and total soluble solids in Grade A and Grade B leaves of the same batch. HPLC revealed < 2 % difference in each metric.

In short, the vessel’s material and its thermal properties dominate flavor outcomes; leaf grade barely shifts the chemical profile.

What do you think? Have you seen a difference in your own experiments? Does this undermine the traditional tea‑grading system, or am I missing something about the subtle aroma nuances that graders emphasize?