Ice is the most important ingredient in drinks. But probably not for the reasons you’re thinking.
Ever since I began working as a bartender in 2006, I immediately had an exchange of words with a lot of customers who asked me for drinks with little ice; the typical phrase was: ”I would like a spritz, but only with three ice cubes.” Initially, I felt offended because I was the bartender and, after considerable training, I knew very well what I was doing. I would have liked my clients not to tell me how to do my job because I would never dare, for example, explain to a mechanic how to change the clutch on my Vespa (Yes, I have a 1980 Vespa. Yellow).
The average client thinks that the bartender puts a lot of ice to save money, while the bartender thinks that putting a lot of ice will water down less the drink.
The truth is that both the client and the bartender are wrong. Let’s try to understand why.
It is only just for customers to ask for less ice (if they don’t like it) but it’s a mistake if they think that the bartender does so in order to save on the products. In fact, the factor that most affects the selling price of drinks, in most cases, is the cost associated with the amount of products used. Even when using less ice, the amount of ingredients needed must remain unchanged because bars are businesses and must have a certain profit on what they are selling in order to pay rent, utilities, staff and general profits to its members.
As far as dilution is concerned, the issue is a bit more complex.
Let’s start by stating that it’s not true, in general, that when using less ice the drink is diluted more.
In order to understand what is going on inside a drink with ice, we have to look at the part of physics called thermodynamics, which describes all the processes involving mass and energy transformation.
In our case the object of study is heat (energy), which tends to move from higher temperature zones towards zones at lower temperatures. This difference in temperature is called thermal gradient. If the thermal gradient is equal to zero, or rather there is no temperature difference, there is no heat transfer. As we will later understand, this principle is of great importance to limiting dilution.
Intuitively we would be led to think that the ice chills because it is cold, but the issue is somewhat more complicated.
A freshly produced ice cube has a temperature of about -19°C. It immediately begins to warm up and in a short time it reaches a temperature of 0°C. From -19 to 0°C ice does not dissolve, yet it absorbs heat only to vary its temperature. The amount of heat absorbed to increase its temperature is called specific heat. This amount of heat is taken away (thus cooling) from what is found near the ice.
When 0°C is reached, the ice begins to melt and a phase transition takes place. From this point onwards, the ice will no longer increase its temperature and it will remain at 0°C until it is completely melted. All the heat that the ice absorbs will be used to melt! The amount of energy absorbed in order for this transition to take place is called latent heat of fusion.
Now that you understand the two reasons why ice absorbs heat from what surrounds it, let’s go back behind the bar counter.
Most of the ice we use in drinks is not produced on the spot, rather it remains in a storage bin or in the workstation tank, the time it takes to reach 0°C, i.e. the temperature at which the state transition takes place; from this moment onwards, it will not absorb heat to warm up but to melt. Hence the ice we use in drinks has a cooling effect because it melts.
There is no chilling effect without dilution.
If we are reasoning with adiabatic glass walls, i.e. insulators, this allows us to understand that the amount of ice does not affect the dilution, and the reason for this is quite simple: in order to bring the drink to a temperature of -2°C you have to give the ice a certain amount of heat, this amount of heat will melt the same amount of ice and it doesn’t matter if the cubes are 5 or 10. Individually, the 5 ice cubes will melt more, while the 10 ice cubes will melt less, but the total dissolved amount will be the same. In other words: at the same temperature reached by the drink, the amount of heat absorbed by the ice that has cooled the drink will have generated an identical dilution whether you have 5 or 10 ice cubes.
What does change is the time it takes to cool: a lot of ice chills (and dilutes) faster.
If, however, you use ice produced on the spot, or just removed from the freezer, you must also take into consideration the amount of heat used to vary its temperature (specific heat). The chilling will take place without dilution. In this case, more ice will chill more and dilute less.
Since dilution in many drinks is needed, what you can do to limit it, at the same temperature of the final drink, is to use liquids that are already cold: sodas and juices, distillates or liqueurs (if possible). The same applies to glasses. In this way there will be less heat transfer.
I’d like to conclude by saying that when making drinks it is always a good idea to use a lot of ice (fill the glass) for the following reasons: it guarantees uniformity and higher chilling speed, it allows to maintain the proportions between ingredients especially when you have to fill the glass with a juice or soda, it keeps the drink cold for a longer time (but with more dilution) and drinks with little ice “are ugly and seem like they’ve already been drunk.”
Our discussion on ice isn’t over. Read my article ‘Ice in drinks: time and dilution‘. You’ll discover what happens when you use little or a lot of ice.
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