Stone Grinding: The Craftsmanship Behind Your Matcha
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It takes about an hour to produce 30 to 40 grams of matcha powder using the traditional millstone. It's slow. And that's exactly what matters.
The Millstone: A Millennia-Old Tool
The millstones used for grinding matcha are disks made of granite or volcanic rock, assembled in pairs. The upper disk rotates slowly over the fixed lower disk. Dry tea leaves (tencha) are slipped between the two and gradually ground.
This system has been used in Japan since the 13th century. It has barely changed since then.
Why Slowness is Essential
The key is thermal. Slow grinding with a stone mill generates very little heat. Heat is the enemy of matcha: it oxidizes chlorophyll (the powder turns yellow), degrades noble amino acids, and alters volatile aromas.
High-speed industrial grinding heats the powder to temperatures that can reach 40-60°C. The powder is already partially oxidized even before it is packaged.
In figures: A traditional millstone produces 30-40g of powder per hour. To fill a 30g sachet, therefore, it takes about 1 hour of continuous grinding. An industrial grinder produces hundreds of kilograms per hour — but the quality obtained is not comparable.
The Fineness of the Powder
Stone mill grinding produces an extremely fine powder — 5 to 10 microns in diameter per particle. This fineness is what allows matcha to dissolve perfectly in water and create a velvety texture.
Poor industrial grinding produces coarser particles, which result in a grittier matcha, harder to dissolve, and which leaves sediment at the bottom of the bowl.
How to Identify Stone-Ground Matcha
- The packaging explicitly mentions it: "stone-ground" or "milled with granite"
- The powder is ultra-fine, almost silky to the touch
- The color is vibrant, emerald green (not oxidized)
- It dissolves perfectly at the right temperature without lumps
Frequently Asked Questions
Can you grind your own matcha at home?
In theory, yes, but traditional millstones are very expensive (several thousand euros) and require specific expertise. Tencha (dry leaf before grinding) is not easily available in Europe. In practice, buying pre-ground matcha remains the only realistic option.
Do all brands use stone mills?
No. Very low-priced matchas are almost certainly industrially ground. Brands that use stone mills mention it because it is a real and verifiable quality argument.
