Cocktail Ice - Part II
The post Good Ice Makes Great Cocktails seems to have resonated with readers. It also raised a number of additional questions regarding this ever so important, but often overlooked, cocktail ingredient. I’ll be answering a few questions and doing some technical talk about the properties of ice. So put your thinking caps on because we are going to learn a little bit about thermochemistry. We’ll also take a look at making clear ice.
If you mix one cup of water at 20°C (68°F)with an equivalent amount of water at 40°C (104°F), what would the resulting temperature of the combined water be? If you answered 30°C (86°F), you’d be correct. Congratulations. Now, if you mixed one cup of ice at 0°C (32°F) with an equivalent amount of water at 20°C (68°F), what would the combined temperature be? If you answered 10°C (50°F), you’d be wrong! The temperature would be 0°C (32°F)? That’s odd, isn’t it.
Water has a lot of unique properties, one of them being the amount of energy it requires to change state. Water and ice can both exist at 0°C, but to convert ice to water requires a lot of heat, and I mean a lot. This heat is called latent heat.
You may be asking yourself if all of this thermochemistry mumbo-jumbo has anything to do with cocktails or if Darcy is just babbling on, and on, to fill the void. Well, this latent heat thing has a lot to do with cocktails, and more specifically how we chill them and why it stays cold. If we know the best way to chill a cocktail, then we’ll make better cocktails.
Here’s a fact for you; it takes 82 calories to convert one gram of ice to one gram of water, at 0°C. If you applied 82 calories to one gram of water at 1°C, it would raise the temperature of that water to 83°C (181°F). That’s hot enough to seriously burn you if you splashed it on yourself.
Basically, it takes a very large amount of energy to convert ice to a liquid. This also means that the chilling properties of ice are perfect for bringing down the temperature of your cocktail, without diluting it with too much melted water.
Many people say you should use ultra-cold ice to make a cocktail, and I partially agree. My personal observation is that ice that is already melting seems to make drinks more dilute, but using ice that’s a few degree’s below freezing seems to work better. I think this has more to do with the water on the surface of the cubes and the handling of the ice that makes it melt. The few extra degree’s below zero seems to give you little working room before the ice melts.
From the scientific side, using ice that is -10°C will only remove 10 calories of heat energy, per gram, from a drink. But when the ice starts to melt it will use up to 82 calories per gram. So the reality is that the “extra cold ice” has a small impact on the overall temperature of the drink, when compared to the effect of the melting ice.
If you want to make a very chilly drink the trick is to use lots of ice, not extra cold ice. Since ice requires so much energy to make it melt, the more ice you have in a cocktail shaker, the quicker it will drop to 0°C and the longer it will stay that way. It is effectively impossible to get a drink to go below 0°C using normal amounts of ice (cocktail shaker quantities) from a standard ice cube maker, so 0°C is the best you can do. Aiming for anything else will be an exercise in futility.
Edit: It is possible to get a drink with alcohol to go below 0°C as the alcohol acts like anti-freeze, but a non-alcoholic one is more difficult and sugar may suppress the temperature by a degree or three, but not much more.
Many people think that restaurant are ripping you off by using more ice in a glass. The reality is that more ice makes for a better drink and keeps it colder longer.
How to Make Clear Ice
Clear ice is great for photographs and looks really good in colourful cocktails. But how do you make it? Ice machines do it by using a layering process with filtered water. At home it is a bit harder but it can still be done.
The first step is to use filtered or distilled water. When water comes from a tap it has small particles that act as nucleating agents, which provide a surface for water crystals to form at a more rapid rate. This can create hazy ice. Snowflakes form this way.
Next, you should boil your water to remove any dissolved gases. When you bring water to a boil you will notice bubbles forming and clinging to the sides of the pot, these are dissolved gases coming out of solution. If you don’t boil your water, the ice will again be hazy.
When you freeze your pure boiled water, it will form ice from the outside inward. But since water expands when it freezes, once the last bit of water on the inside of the cube turns to ice, it will expand and crack the ice with little micro fractures. Think about what happens to a beer bottle when you put it in the freeze for too long.
To avoid this expansion issue, you can simply poke a hole in the top ice layer just after it freezes. This will give the water inside a place to go, without cracking the cube.