Hints to make clear ice

  • 31 Dec 2016
  • Jack Chu

A close looks at an ice cube will disclose air bubbles and particles, which can reflect light and make the ice cube look cloudy.

Here I want to explain the reasons for causing cloudy ice and needle bubbles, and bring forward the methods to solve the problems by using Polar Ice Tray.

The relation between the ice freezing rate and the transparency

  • When the freezing speed is fast, it will trap tiny air bubbles between the ice crystals. The air bubbles diffuse the light, and cause the ice look cloudy white.
  • When the freezing speed is a little more slowly: the tiny air bubbles will be pressed in freezing direction, and become to bigger bubbles. The larger bubbles may leave behind needle-like trails in the ice.
  • The freezing speed is slow enough; the air will not be squeezed out to become bubbles. It will keep dissolved in the un-freezed water.
  • Clear ice with high transparency has a good crystal structure, higher hardness, and a slower melting rate.

    The relation between the impurity and the transparency

    The impurity will block the water molecules to form ice crystal, and create more space to trap air bubbles. The cloudy ice is not soft, and very easy to melt.

    Some water cannot produce clear ice

    Water contains some particular materials (as dissolved salt) will not produce clear ice. We design an experiment to show how the salt will affect the transparency of ice ball.

    The experiment procedures:

    1. Dissolve salt in tap water: 0 for no salt; 1 for one tea spoon of salt; 2 for two spoons of salt

    2. Put the Polar Ice Trays into freezer at same condition.

    3. Compare the results

    Comparison Table

    * TDS: Total Dissolved Solids
    * ppm: Unit of Concentration (part per million)

    Hints to prevent needle bubbles

    Decrease the air dissolved in the water

    • Use boiled water: Sometime it works. Air can be driven out of water by heating it. But air will get back into boiled water fairly quickly.

    Decrease the air bubbles been trapped in the mold:

    • Pour water slowly
    • Tap on the silicone layer with your finger to dislodge the bubbles

    Prevent the air bubbles floating up: The bubbles will float up during the freezing process. You can resolve this problem by:

    • Open / Close the freezer door lightly
    • Do not move the tray during the freezing process

      Hints to prevent cloudy ice

      If the cloudy ice distribute in some particular place (top, side or bottom), the problem is that freezing speed in the area is too quick:
      There are some ways you can try to resolve this problem:


      Polar Ice Tray – Polar Ice Ball is the most effective structure we found up to now. We will keep on study the features of clear ice, and will try to find new way to let the ice making more easy and more independent from the environment (no matter the condition of freezer).

      If any question or good idea, please feel free to contact us at info@polaricetray.com.


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