What Is Stone-Milled Matcha and Why Does It Matter?
Most matcha sold in the UK is not stone-milled. The label rarely says how it was ground, and most buyers never think to ask. But the milling method is one of the most significant variables in what the finished matcha actually delivers, and understanding what stone-milling does and what industrial alternatives do instead changes how you think about every tin you open.
What stone-milling actually is
Traditional matcha is ground using granite millstones. Two heavy stones rotate against each other at a very slow speed, typically between 20 and 30 rotations per minute. The tencha, the de-veined and dried tea leaf that is the raw material for matcha, is fed gradually between the stones and ground into a fine powder over an extended period.
At that speed and with that method, a single stone mill produces between 30 and 40 grams of finished matcha per hour. That is not a typo. Thirty to forty grams. Per hour. Per stone.
The slowness is the point. It is not a limitation of the technology. It is what the technology is designed to do.
Why slow grinding matters
Speed generates heat. This is true of any mechanical grinding process. When you grind something quickly, friction between the grinding surfaces and the material being ground raises the temperature of the output.
Matcha is sensitive to heat. The compounds that make ceremonial grade matcha worth drinking, L-theanine, EGCG and chlorophyll, begin to degrade when exposed to elevated temperatures. Industrial milling at high speed generates enough heat during the grinding process to start breaking down these compounds before the powder ever reaches the tin.
Stone-milling at 20 to 30 rotations per minute generates almost no heat. The compound profile of the tencha is preserved through the grinding process and arrives in the finished powder intact. The first flush, shade-grown leaf that went into the process comes out the other side with its L-theanine, EGCG and chlorophyll levels effectively unchanged.
What industrial milling does instead
Industrial ball mills, hammer mills and similar high-speed grinding equipment can produce matcha powder in dramatically higher volumes than stone mills. The output per hour is many times greater. The cost per gram is significantly lower. For a brand trying to produce at scale and keep prices competitive, the commercial logic is obvious.
The trade-offs are real. The heat generated during high-speed milling degrades the compound profile. The particle size produced by industrial milling is less consistent than stone-milled powder, with a wider range of particle sizes rather than the even, fine distribution that stone-milling produces. Less consistent particle size means a less stable suspension in water, which means the powder settles faster, the froth is less stable, and the texture of the finished drink is different to what a stone-milled matcha produces.
Why particle size matters for what ends up in the cup
Master's Reserve is stone-milled to 10 microns. That is a specific claim about particle size, and it matters for three reasons.
First, froth. A finer, more consistent particle size produces a more stable suspension in water during whisking. The froth that forms is finer and holds longer. This is part of why the froth test is a reliable quality indicator. A well-made stone-milled matcha produces a fine, stable froth that a coarser, industrially milled product cannot match regardless of preparation technique.
Second, suspension. A more even particle size means the powder distributes more evenly through the liquid. The compounds present in each particle are more uniformly available throughout the drink. The texture is consistent from the first sip to the last rather than shifting as the heavier particles settle.
Third, mouthfeel. A 10-micron particle is imperceptible on the palate. A coarser grind can produce a slightly gritty or heavy texture that is noticeable in the finished drink. Stone-milled matcha at 10 microns is completely smooth.
The question worth asking
Most matcha brands do not tell you how their matcha was milled. The label says ceremonial grade. It says organic. It might say the origin. The milling method is almost never disclosed, because disclosing it would require either telling the truth about industrial grinding or investing in stone-milling infrastructure that most brands are not willing to fund.
The next time you are buying matcha, whether online or in a shop, ask or look for confirmation that it was stone-milled. If the brand cannot tell you, or the information is not on the label, it almost certainly was not.
Master's Reserve is Okumidori from Wazuka, Kyoto. First flush, 21 days pre-harvest shading, stone-milled to 10 microns, JAS certified organic. Every detail on that label is there because it changes what ends up in the cup.
Master's Reserve is available now, delivered across the United Kingdom.