Have you ever purchased a bag or ice or received some iced soda at a restaurant and noticed how clear the ice is? Why is bagged ice and restaurant ice so clear when the ice you make at home often appears white and cloudy?
Why Is Bagged Ice So Clear?
While some bagged ice you buy is white in color a lot of bagged ice you purchase is completely clear or nearly clear. But why is bagged ice clear whereas the ice you make at home tends to be cloudy and white?
Bagged ice is clear because it's frozen from the inside out pushing out the air bubbles that usually make ice opaque. Clear bagged ice is usually made from filtered water which is free of minerals and impurities which can often make ice cloudy.
The higher quality the water the clearer the ice is likely to be. Many ice manufacturers have their own filtration system to remove impurities and other minerals in the water. The water may also be softened to further remove excess calcium and magnesium.
Small air bubbles are what usually give ice is opaque/white appearance and commercial ice manufactures usually freeze ice from the inside out. The pushes the air bubbles out as the ice freezes, leaving the ice clear and transparent.
Above you can see one commercial ice machine making clear ice cubes from the inside out.
How Do Restaurants Get Clear Ice?
The ice at restaurants is almost always much clear than the ice you'd find in your own freezer at home. But how do restaurants get such clear ice?
Restaurants get clear ice by using an ice machine that constantly flows filtered water over the ice as it freezes from the bottom up. The process removes minerals, impurities and air bubbles from the ice leaving it crystal clear and transparent.
If restaurants tried to freeze ice like you and I do at home not only would it take a lot longer but their ice would be white and also probably wouldn't taste as good.
Restaurants usually filter their water before making ice meaning the ice itself is free of impurities and minerals which also helps it to appear more clear.
Above is a video on exactly how the ice machines used to make clear ice in restaurants are made. Towards the end of the video they should you exactly the process the machine uses to make ice.
You can see the water flowing over the cold metal grid freezing from the bottom and working its way forward while water continues to flow.
Once the ice cubes are full size the release mechanism is tripped. Water stops flow, the metal grid heats up and the clear ice is released into the collection bin below
Why Is McDonalds and Other Fast Food Chains' Ice So Clear?
Ever wondered why the ice in McDonalds and other fast food chains' ice is so clear?
McDonalds and other fast food chains' ice is so clear because their ice machines freeze ice from the bottom up pushing out the air bubbles and making it crystal clear. They also use filtered water which contains fewer minerals and impurities.
McDonalds ice is made by having filtered water flow over a metal grid that is made extremely cold by refrigerant pipes directly behind it.
As the water flows over the metal grid it begins to turn to ice. Ice is build up layer by layer from the bottom to the top. During this process there is constant stream of filtered water and this removes air bubbles, minerals and impurities from the ice. This makes it free of bubbles and impurities allowing it to look crystal clear.
Once the ice has become thick enough it will trigger the release mechanism. The water will stop flowing and the metal grid will now heat up to allow the ice to drop into the collection bin below.
Below you can see a quick video of an ice machine that works in a similar way to McDonalds ice machines and ice machines used at other fast food chains.
McDonalds state in their answer to this question:
Only filtered water is used to make our ice cubes in our restaurants, the same filtered water that is used for beverages like soft drinks and coffee. We wash, rinse and sanitize the ice scoops and ice buckets used to transport ice from the ice machine to our dispensing machines every day. We also wash, rinse and sanitize the ice machine itself every month.
Why Does Restaurant Ice Last Longer?
Ever wondered why ice at a restaurant seems to last longer than ice you make at home? There are a couple of main reasons for this.
Ice at restaurants last longer because restaurants use clear ice cubes which are free of air bubbles and melt slower than regular ice cubes. Also restaurants tend to put A LOT of ice in each cup, making the drink colder overall, which makes the ice melt slower.
Some restaurants keep their ice at temperatures colder than your freezer at home, meaning it takes longer to melt.
Also regular soda is denser than water so ice will melt slower in soda than in water. Given when people go out to restaurants they are likely to order soda, but when at home they are more likely to drink water this could also explain why the restaurant ice seems to last a lot longer than ice at home.
There is nothing special about a restaurant environment that makes the ice melt slower (unless it's heavily airconditioned). It's the ice itself and how much ice is used that causes it to melt slower.
Most restaurants use half cubed ice but some use full cube ice which lasts even longer. Above you can see a video about how full clear cubes of ice are made in restaurants, bars and anywhere else that sells drinks with clear ice.
Why Do Starbucks Ice Cubes Melt So Slowly?
Have you even ordered an iced coffee from Starbucks and been baffled by how long the ice lasted in your coffee compared to say ice in a similar cup of water? Why is this? Why does Starbucks ice seem to last so long in your drinks?
Starbucks ice cubes melt slower because they are made of clear ice which is denser and also because the milk coffee is denser than water, so as the ice melts it stays on the top of the drink and doesn't mix in with the drink easily.
No convection currents are created in the drink that would usually push the warmer part of the drink up towards the ice melting it faster. The ice cube in your Starbucks coffee remains in contact with the cold melted water, slowing its rate of melting. Thus the ice in Starbucks coffees tend to last longer than if you put the same ice in a glass of water.
Below you can see an experiment where an ice cube is placed in fresh water vs salt water.
The melted ice cube in the salt water forms a distinct layer that floats on top of the salt water but with the fresh water it melted and sunk to the bottom and spread out evenly, creating convection currents in the water.
In the regular water these convection currents push the warmer water from the bottom of the cup up towards the ice cube, melting it faster. In the salt water this doesn't happen and so the ice melts slower.
This is the same process that happens in your Starbucks
Is Clear Ice Healthier?
Clear ice looks better and sometimes even tastes better than cloudy ice. This may make you ask. Is clear ice healthier?
Clear ice is usually made with distilled or filtered water which removes the impurities and natural minerals found in the water. While this process removes potentially harmful contaminants it also removes natural minerals and electrolytes found in water so clear ice isn't necessarily healthier.
You can make clear ice with tap water that isn't filtered, however it's more difficult and more likely to have impurities and cloudiness compared to distilled or filtered water.
Clear ice also melts slower than cloudy ice meaning it'll dilute your drink less and you'll taste less of the ice in your drink. Using large square or round clear ice cubes in drinks like whiskey dilute your drink less and give you a purer drinking experience.
Below you can see a video of a Hoshizaki machine and how it makes clear crescent shaped ice: