R & D Logbook

We tested every method we could, and thoroughly researched the ones we couldn't test. If you love the science of clear ice as much as we do, please enjoy reading our notes.

 

Method

Heated and/or boiled water in a normal ice cube tray, placed in a home freezer.

Theory

Heating water causes it to expel dissolved gasses. 

Test result

This is the most common belief. In reality, it is only partially effective. As the water cools it re-dissolves gasses from the surrounding air. By the time ice forms, it is cloudy. The ice is less cloudy than non-boiled water, but is not glass-clear. If the water could be flash-frozen, this might work, but in a home freezer this does not work well.


Method

Low-Frequency mechanical vibration during freezing.

Theory

Vibrate water as it cools and it will freeze slowly. This way, dissolved gasses will escape during the freezing process.

Test result

It takes a little longer but the exposed surface freezes first – as usual. The remaining dissolved gasses get trapped in the water below.  Cubes are cloudy.

 


Method:

Thermoelectric (Peltier) cooling.

Theory

A super-cooled surface can freeze water from the bottom-up. The top will freeze last. Dissolved gasses will escape from the water at the the exposed air-water interface. 

Test result

Peltier coolers are inefficient. A cooling surface large enough to produce a set of ice cubes could use upwards of 1000 watts. There must be a large temperature difference between the hot and cold sides of the thermoelectric element. The bottom of the element requires a large heatsink and cooling fan to maintain this. The device becomes a large, power-hungry beast.


Method

Air-agitated freezing. 

Theory

Agitate water with air bubbles while it freezes. Dissolved gasses will escape late into the freezing process. The dissolved gasses escape through an unfrozen air-water interface at the bubbling site.

Test result

This process can work, but it requires a large volume of sacrificial malformed ice. The resulting good ice is difficult to separate from the bad ice. It also requires continuous power during the freezing process.

Method

Distilled and/or filtered water in a normal ice cube tray, placed in a home freezer. 

Theory

Purer water contains fewer particles to act as nucleation sites.

Test result

Two problems. First, no water is pure enough. Second, gasses don’t need nucleation sites to come out of solution and get trapped inside the ice. Purified water alone does not make clear ice.


Method

Ultrasonic vibration during freezing.

Theory

Water bombarded with ultrasonic frequencies while freezing will expel dissolved gases.

Research findings

Some large scale commercial ice makers work using this technology. This process was patented more than fifty years ago. Ultrasonic emitters of the power required are large and power hungry. A home unit using ultrasonics would need to be an expensive free-standing appliance. Or,  a large unit with a power cord running into the freezer!


Method

Accumulated thin-layer freezing.

Theory

This is the way icicles form, and icicles are clear. Water accumulates in thousands of ultra-thin layers, and freezes.  Each layer is thin enough that gasses are able to evaporate as it freezes.

Research findings:

Many large-scale commercial ice makers use this principal. These ice makers have an array of chilled metal fingers. The machines blow mist over the fingers and deposit layers of ice. You often find these cubes in hotels and can recognize them by the holes in their centers. To do this at home would require a dedicated appliance.


Method

Insulated top-down directional freezing.

Theory

This is how ponds and lakes freeze in nature. Beneath the surface of a frozen lake is clear ice. All clear-ice makers for the home freezer work this way. This is an non-patetentable physical process of nature.

Test results

This is the only working method that does not need outside power.  Directional freezing itself is easy. Getting it to work without usability difficulties or ice deformations is difficult.

Water expands by 9% when it freezes. This expansion causes increased pressure on the liquid water. This pressure introduces many problems, including: cubes that maintain some cloudiness, strange "skyscraper" ice extrusions, and cloudy-topped bubbled-up cubes.

Most solutions to this problem introduce usability issues including: very large water reservoirs that take too long to freeze, trays that are difficult to remove, complex designs that need three or more interlocking parts, designs that can't make more than one cube shape without introducing distortions.

Over many years of trial and error we have arrived at a solution. This patent-pending solution allows pressure to equalize during freezing without introducing any usability issues.