Chapter 2 - How can I select my water type?

Based on tests conducted on dozens of water sources, we have found that water with a TDS level between 30–50 mg/L tends to produce significantly clearer ice. Water with TDS levels either above or below this range typically results in less transparent ice.

From our experience, we can infer that mineral water, filtered tap water, and some municipal tap water often fall within this optimal TDS range and are therefore more likely to produce clear ice—though actual results depend on the specific characteristics of the water source used.

Purified water, due to its extremely low ion concentration (always 0), often leads to the formation of needle-like air bubbles within the ice. Conversely, water with higher ion concentrations can cause the bottom of the ice block to appear cloudy.

In the following section, we compare the effects of different TDS levels on ice clarity and outline the patterns we have observed.

Purified water - A | TDS 0

Purified water - B | TDS 10

Mineral water - A | TDS 34

Mineral water - B | TDS 44

Mineral water - C | TDS 52

Tap water HK | TDS 59

Mineral water - D | TDS 119

Mineral water - E | TDS 176

Mineral water - F | TDS 231

As shown in the image series, we conducted sampling tests on water sources with TDS levels ranging from 0 to 230 mg/L. These sources included distilled water such as Watsons, purified water like Bonaqua, and a variety of mineral waters with increasing ion concentrations—including Fiji, Evian, VOSS, Acqua Panna, and Dasani... The trends we observed were as follows:

At TDS levels of 0 and 10 mg/L, needle-like air bubbles appeared within the ice. As the TDS increased, these bubbles became less pronounced and eventually disappeared. At a TDS level of 34 mg/L, only minimal bubbles were visible in the ice sphere. When the TDS fell within the 44–59 mg/L range, the ice spheres became fully transparent. Beyond 100 mg/L, the bubbles reappeared in a more granular form, resulting in a cloudy appearance. Among the mineral waters tested, Evian had the highest TDS value.

Our findings confirm that while we recommend using mineral water with an appropriate TDS level to produce clear ice—especially given its compact volume, which makes it ideal for freezing multiple ice shapes even in smaller freezers—mineral water is not the only viable option.

Properly filtered or naturally balanced tap water that falls within the optimal TDS range can also produce crystal-clear ice, making it a practical and accessible alternative for many users.

In the next section, we will explore how the choice of water impacts freezing speed and structural integrity of the ice.