If you’ve ever treated yourself to a big glass of afternoon iced tea or an evening scotch on the rocks, you may have noticed your ice cubes are white in the middle. There’s actually an interesting reason for this.
Ice is white in the middle because it freezes from the outside to the inside. Because the outer edges freeze first, air bubbles become trapped in the water and are forced to the center of the ice. Impurities in the water can also cause cloudiness in ice cubes.
In this article I’ll explain more details about why ice is white at the center, how to get white ice and even how to get those pesky air bubbles out the ice so you can make completely clear ice.
You'll learn about the processes behind freezing ice, factors affecting ice color, and how to make beautiful crystal clear ice cubes or spheres.
Reasons Why Ice Is White in the Center
When you make ice using an ice cube tray or silicon form, you know that the water you add is clear, yet the ice still comes out cloudy or white. Ultimately, there are a few reasons for this.
The Freezing Process of Water Into Ice
The first culprit behind white ice has to do with the way in which ice freezes.
When you place an ice cube tray in the freezer, the cold air first contacts the exposed surfaces of the water. If you pull an ice cube tray out of the freezer too soon, you’ll notice a delicate layer of ice formed at the top of each cube; however, the water beneath is still liquid.
This top later now stops any air bubbles from escaping the ice as it freezes.
Next the ice will freeze from the sides and base, slowly working its way inwards. As this happens the air bubbles get pushed into the middle of the ice cubes where they get stuck and then freeze over.
The white you see inside the ice cube is usually a bunch of frozen air bubbles.
Air Bubbles Trapped Inside
You may also notice tiny air bubbles inside ice cubes. This is because water at room temperature contains a certain amount of soluble air; the air molecules (mostly nitrogen and oxygen) essentially “wiggle” their way into and out of the water.
As the water freezes from outside in, air molecules become trapped by the outer shell of ice. These bubbles can be very tiny, and basically invisible to the naked eye, and as they are pushed into the center of the ice, they begin to accumulated together eventually freezing to look like a solid white mass.
If you look very closely at an ice cube, you may be able to see that the white center is a collection of tightly packed air bubbles.
Above you can see sphere of ice which is mostly clear but has a few air bubbles in it. In a regular ice cube there are a lot more air bubbles than this.
The air bubbles look white, but this is due to the way light is bent and refracted as it passes through the air bubbles. They aren't actually white in color.
Impurities in the Water
Another reason your ice may be cloudy, white, or discolored is due to impurities that may be present in the water.
Common impurities in tap water include chlorine, fluoride, and metals such as iron, cadmium, arsenic and even lead. These can affect the taste of your ice and create cloudiness and color if impurities are found at high levels.
Distilled water is best for making clear ice as it contains fewer impurities, which are left behind when the distillation process evaporates the water. Distilled water is best for making clear ice as it contains
How To Make White Ice
RIGHT: Regular ice from tap water with only some bubbles in the center
If you want to make ice that is very white and opaque then there are a few different methods you can use. Some ice makers like the Opal Nugget Ice Maker make ice really quickly which tends to make white ice cubes due to the way they form but a great ice cube tray hack is to simply fill up your ice cube tray with carbonated water.
This contains CO2 gas which as the ice freezes wants to escape and in doing so it'll make very bubbly and cloudy ice as you can see above.
Why Is Some Ice Clear?
Ice forms clear when the air bubbles are pushed out of the ice rather than inward. This process occurs when ice freezes in one direction, such as top-down or down-up, and the air pockets are forced out through one side.
If you’ve ever been served a cocktail at a classy bar or restaurant, you may have noticed that these establishments often use crystal-clear ice cubes. There are a handful of reasons why this tradition persists. Clear ice is usually better than white ice for cocktails and premium drinks. It melts slower diluting your drink less and often looks and tastes better than white or cloudy ice.
Here are a few reasons why clear ice, or “gourmet ice,” is preferable to white ice in drinks:
- Melts Slower: Clear ice is denser as there are no air bubbles and it melts slower than white ice. This is because clear ice has less surface area exposed to air. The slower melt of clear ice means it won’t melt and dilute a beverage as quickly and keeps the drink cold for longer. If you make the ice using a good large ice cube tray it'll melt even slower
- Better taste: Clear ice is usually made using distilled water which, as mentioned above, contains fewer impurities like chlorine and heavy metals affecting taste. Clear ice can also taste better than white ice because it does not have air bubbles. White ice can trap smells and odors from the air in your fridge/freezer, which may cause the ice to taste foul over time.
- Smoother texture: White ice has a more crunchy feeling than clear ice, which is smooth. While some people prefer the crunch of white ice, others delight in a smooth ice cube.
- Aesthetically appealing: One of the most obvious reasons bartenders use clear ice in cocktails and other beverages is its visually pleasing appearance. The smooth sides allow light to pass through the cube and highlight the color of the liquid. Simply put, clear ice looks fancy.
How To Make Clear Ice
Gazing into a perfectly clear ice cube will probably make you wonder: how do they do it?
Commercial clear ice makers usually have ice machines that freeze ice from the bottom up and pumped that generate a constant, steady stream of flowing water to remove air bubbles. As the water slowly freezes (from bottom to top, typically), the air can escape in the stream, similar to how ice forms over the top of a river.
If you don’t have an industrial ice maker at home, don’t worry. You can still make crystal clear ice at home using distilled water and a clear ice maker. These are usually ice molds with insulated sides (like a cooler) that encourage the ice to freeze from the top down pushing the air bubbles into the bottom of the mold leaving the ice at the top crystal clear.
I personally use the Tovolo Ice Sphere Maker (amazon) which makes 4 fairly clear ice spheres at a time and I rate as one of the best ice ball makers on the market.
Read my article to learn how to get clear ice at home. Don’t have any distilled water on hand? Check out my article on making clear ice with tap water.
Here’s a quick run-down on how to make clear ice at home even if you don't have an ice sphere mold like I do:
- Make the water as pure as possible by purchasing distilled water or purifying and distilling it at home.
- Fill a large cooler or insulated container with water. The container will need to be able to fit in your freezer. Do not fill over ¾ full.
- Place the container in the freezer without any lid.
- Set the freezer temperature as cold as possible. The top exposed portion of the water will freeze before the rest, which is insulated by the cooler.
- Remove the cooler when most of the water is frozen. The remaining water at the bottom of the cooler contains air molecules and impurities, so you’ll want to leave them out of your ice.
- Remove the ice block from the cooler after a few minutes.
- Break the ice with a hammer or cut with a serrated knife.
If you want perfectly smooth and clear ice with minimal hassle, you can also consider purchasing a special clear ice tray, such as the True Cubes Clear Ice Cube Tray (amazon). Proven to remove 98% of metals and TDS, it’s made of a BPA-free silicone and uses a natural freezing method to produce perfectly clear ice every time.
See the latest price of True Cubes at Amazon
Conclusion
Ice is white in the middle for a number of reasons, including trapped air bubbles, water impurities, and the way water naturally freezes. However, it’s easy to make clear ice at home, and you’ll find, whichever method you choose, it’s well worth the extra effort. Follow my simple guides, and you’ll be sipping with a clear mind in no time.
