Does soft water suit oolong tea brewing?
Soft, low-mineralization water is generally the better choice for brewing Phoenix Dancong and other oolong teas. It brings out sweetness, freshness, and clarity in the liquor, while hard water tends to add astringency and scum. Water quality often matters more than technique, and starting with low-mineralization soft water lets the layered aromas of oolong come through.
Tea masters long favored spring water; Lu Yu's eighth-century Classic of Tea praised water from stone pools on pristine mountainsides. Modern science explains the effect through TDS, hardness, and pH levels, and the article cites industry reference values from the American Tea Association along with several studies. There is still no single agreed answer, since tea types and personal taste both play a role.
When brewing a good cup of tea, water quality is often more critical than technique. As early as Lu Yu's "Classic of Tea," spring water was held in the highest regard, while modern science has revealed the reasons behind this through TDS, hardness, and pH levels. This article focuses on the brewing water for oolong teas such as Phoenix Dancong, outlines the industry reference values from the American Tea Association, and cites multiple studies to explain why soft water enhances the sweetness, freshness, and clarity of tea liquor, and how hard water brings about astringency and scum. For tea lovers who cherish the complex aromas of oolong tea, choosing the right water is the first step in releasing the charm of the tea. Front Street Coffee also recommends starting with low-mineralization soft water to experience the subtle changes in the layers of the tea liquor.
Long before the goat in Kaldi's tale accidentally tasted coffee cherries, tea connoisseurs already understood well the important influence of water quality on brewing. Lu Yu, the Sage of Tea in the eighth century, favored spring water, describing in his "Classic of Tea": "The best spring water comes from stone pools on pristine mountainsides, flowing slowly." Choosing the right water for brewing tea was considered such an important matter that certain famous springs became renowned for their suitability for tea, drawing tea lovers from all around to make special trips to visit them.
Although the mineral content of brewing water can significantly affect the appearance and taste of tea liquor, there is still no unified conclusion on what kind of water is best for brewing tea. Instead, different tea types seem to have their own preferences, and personal taste preferences also play a role. Some tea lovers are drawn to a particular water for inexplicable reasons, such as the water's "qi," or the geographical distance between the water source and the tea's origin. Winemakers even drop a few stones into a pot to mineralize the water or give it the terroir character of a certain place. Choosing the right water for a specific tea is regarded as part of the art of brewing, inseparable from the accumulation of long-term experience.
However, this article intends to take a more down-to-earth approach and delve deeper into this topic. Modern science has confirmed the importance of mineral content in brewing water and has provided us with some clues to explain why certain waters are best for brewing certain types of tea.
Brewing Tea with Soft Water
The most widely cited industry guideline comes from the American Tea Association, and its range is broad, not much different from the water we use for brewing coffee: 6 - 8ph 50 - 150ppm TDS (Total Dissolved Solids) Total hardness 80ppm
However, most tea experts point out that water on the softer end of this range is best for brewing specialty teas. Yu Minhong himself may prefer high-mountain spring water precisely because high-mountain springs have short contact time with bedrock, making the water relatively soft.
Most studies published on this topic have reached similar conclusions. One study compared the effects of brewing different tea types with tap water (about 200ppm), bottled mineral water (70ppm), mountain spring water (20ppm), and purified water (Xu et al. 2017). The researchers found that water with low mineral content produced better taste, and mountain spring water performed best overall. Increasing the hardness of brewing water weakened the tea's bitterness, sweetness, and umami while enhancing astringency.
Tea brewed with low-mineral water also looks better. Hard water forms two kinds of solid precipitates in tea liquor: one is the well-known "scum" that forms a film on the tea's surface, and the other is "tea cream"—the cloudy solids that precipitate when tea cools. Tea brewed with soft water is clearer, lighter in color, and less prone to forming scum.
Some have found that the pH of water is also a key variable. They adjusted tap water to pH 6 by adding acid, roughly equivalent to the pH of mountain spring water. This improved the taste and clarity of the tea but did not fully compensate for the difference in hardness.
Another study also found that water with low hardness and low pH helps brew better tea, but also pointed out that green tea seems more susceptible to the mineral content of water than black tea. This is very likely because catechins play an important role in the taste and appearance of green tea.
Xu et al. found that the pH of water is also an important factor. They adjusted the pH of tap water by adding acid until it reached 6, roughly the same as the pH of mountain water. This improved the taste and clarity of the tea but did not fully compensate for the difference in hardness.
Another study also found that water with low hardness and low pH is conducive to brewing better tea, but also pointed out that green tea seems more affected by the mineral content of water than black tea. This is very likely because of the importance of catechins in the taste and appearance of green tea.
The above content is compiled by CoffeeHunters, a coffee news website.
