The leaves used to make matcha are also used to make another excellent tea, gyokuro. To perfect matcha, shading is essential. Shading the plants slows down their growth, increases chlorophyll levels, and transmutes the leaves into a darker shade of green. More amino acids are produced, including theanine, the amino acid that gives tea its calming effect. The leaves are then stripped of their twigs and veins, so only the softest parts that will crumble and be ground easily into dust remain. The method in which the leaves are ground is using a millstone. This process is time-intensive because the stone mustn't get too hot, or the aroma of the matcha will be changed. It takes about one whole hour to grind 30 mg of powdered green tea properly.