Clear ice is becoming increasingly popular in cocktail bars and restaurants because it looks clean and refreshing and really adds to the presentation of a drink. It's also stated to last longer and melt slower. But does it last longer and melt slower than other ice?
Clear ice lasts longer and melts slower because it is denser than opaque ice as it has no ice bubbles. Due to its increased density, clear ice requires more time and heat energy to melt, hence its longevity. Clear ice also tends to be larger than regular ice which also causes it to melt slower.
This article will discuss why clear ice lasts longer, why white ice does not, the science behind that, and what you can do to make your clear ice last even longer than it otherwise would. Read on for details.
Why Clear Ice Lasts Longer & Melts Slower
Clear ice lasts longer than white ice for several reasons. But before we get to those reasons, we need to review how clear ice is made briefly. This way, the science behind why it melts slower and lasts longer will be easier to understand.
To make clear ice, you need to ensure that there is no oxygen in the ice (air bubbles) and that there aren't impurities in the water. The best way to do this is by using directional freezing (ie. Freezing from the top down or bottom up) as well as using distilled water for clear ice, or filtered water to remove minerals and impurities which can make the ice appear more cloudy.
This method pushes the air bubbles and impurities out of the ice as it freezes leaving you with mostly completely clear ice that you can use in your drinks. This way, only the last bit of ice will have any cloudiness and this can be removed.
Because there are no air bubbles or impurities, the resulting clear ice has a higher density when compared to regular ice which contains air bubbles.
Higher density ice takes longer to melt because the lack of air bubbles gives it more mass. The more the mass, the more the heat energy required to melt the ice.
If you make cloudy ice cubes these are even less dense than just regular ice cubes and melt even faster, which is proof that the density and lack of air bubbles causes the ice to melt slower.
The higher density resulting from the lack of air bubbles and impurities may be the main reason clear ice lasts longer, but it’s not the only one.
Here are a few other explanations:
Air Bubbles in White Ice Increase Surface Area, Increasing the Speed at Which It Melts
Another scientific aspect to look at is the surface area. The more surface area an ice cube has proportionate to its volume, the quicker it will melt.
So the shape of the ice cube also matters. This is an important thing to keep in mind when wondering how fast an ice cube will melt because the amount of time required to add heat depends on the surface area of the ice cube.
If you had a large surface area block of white ice the ratio of surface area to volume would be larger, and thus melt faster. This is because white ice contains a lot of air bubbles and the air is less dense than water.
You can increase the surface area of your ice by experimenting with different ice shapes or by increasing the size of the block of ice you are making.
Some people prefer ice spheres in their whiskey compared to ice cubes as these have less surface area and thus in theory melt slower and dilute the drink less.
Clear Ice Is Usually in Large Blocks, Which Melt Slower Than Smaller Ice Blocks
Clear ice is usually made in larger sizes than regular ice. Clear ice cubes are often 2 inches in size and clear ice spheres are the same – see the best clear ice sphere trays.
These tend to look better and more striking, as people have grown to expect regular sized ice cubes.
The scientific explanation of why you would typically find clear ice melts slower in large blocks is the amount of surface area to volume ratio as well as the total volume being much higher as well.
The larger the block of ice, the smaller surface area to volume ratio there is. Here is a great video that explains surface area to volume ratio:
Having a lot of smaller ice cubes increases the surface area to volume ratio, causing the ice to melt faster. You will want to make your clear ice in as large a block as possible if longevity is a concern.
Do You Need To Use Distilled Water To Make Clear Ice?
Having discovered that the lack of impurities is one of the reasons why clear ice lasts longer, you might be wondering whether you need to use distilled water to make it. After all, distilled water has fewer impurities than tap water.
Distilled water makes clearer ice than tap water containing impurities. It’s easier to make clear ice this way because distilling removes impurities that would taint the ice. While you may be able to make clear ice with tap water, you’d need to boil it first to get rid of impurities.
Using water without impurities also causes the ice to begin melting at a higher temperature compared to ice with impurities.
Salt is commonly used to melt ice because the salt impurities make the ice melt at a lower temperature (eg. The ice will begin to melt at -9ºC instead of 0ºC). So the more impurities the earlier your ice will begin to melt. Items like vinegar melt salt earlier and so do other alternatives to salt for melting ice.
In short, the more impurities in your ice the faster it will melt. So by making clear ice free of impurities it'll melt slower than regular ice.
You can use several choices for water when making clear ice cubes. Purified or distilled water is best, and you can buy it at the store. You can distill tap water at home if you want to save money.
Ideas To Make Your Clear Ice Last Even Longer
Now that you know that clear ice lasts longer than white ice, you may wonder if there are other ways to make the ice longer-lasting. It turns out there are a couple of things you can do.
Here are the best ways to extend the life of your clear ice:
- Make bigger ice blocks. The larger the container you use to make the clear ice, the smaller the surface area to volume ratio is. When the surface area to volume ratio is smaller it will take longer for your ice to melt.
- Make spheres instead of blocks. Spheres have a smaller surface area to volume ratio than other shapes. So by making ice in that shape, you decrease the surface area to volume ratio, which helps the ice melt slower.
- Decrease the temperature of your freezer. If you decrease the temperature of your freezer, you are ensuring that you are getting the ice as cold as possible. Having the ice as cold as possible increases the heat energy required to get it to its melting point, increasing its longevity.
- Pre-chill the drink. Rather than placing ice into a room temperature drink, pre-chill your drink in the fridge or in a cooler before placing ice in it. Read about how long it takes a drink to cool down in a cooler.
After looking at various factors, it is apparent that clear ice melts slower and lasts longer than white ice. This has a lot to do with the following:
- The density of the ice.
- The surface area of the ice.
- The number of impurities in the ice.
Removing the air bubbles and impurities from ice using directional freezing will increase the ice's density. This denser ice requires more heat energy to melt and thus takes more time to melt. The fact that clear ice comes in big blocks also contributes to its slower melting.