Why does ice you buy from the store have holes in the middle? Also, why are they more clear than what a home icemaker produces?
In: 435
The answer is down to gravity.
Commercial ice machines that specifically advertise as being able to generate clear ice do so by freezing the water into ice from the top down where the water at the top begins to freeze and solidify before the water at the bottom. As the water freezes, everything in the water is forced to the bottom and this is removed. Contrary to what most people believe, trapped air in the water does not make the ice cloudy (Unless there is lots and lots of it), it’s all the bits that aren’t actually water in the water that cause this cloudiness such as minerals, chemicals, etc.
You can see this for yourself. Get a small icebox, fill it with water and put it in a larger freezer minus its lid. As the water begins to freeze, it will freeze from the top down but the water at the bottom will remain insulated and in water form for a lot longer. As a result you will get clear ice on the top and cloudy ice on the bottom if you allow it to freeze all the way through.
The reason most commercial ice has holes in it is because it is formed by slow dripping water on a metal rod that is suspended vertically and uses a cooling technique (Similar to how a can of deodorant gets really cold when you spray it) to attract water to it and begin to freeze it. This rod is vertical so the water that hasn’t frozen yet can slowly run down the frozen ice and drip away through gravity, carrying the impurities with it and thus only clear ice remaining. Then when its ready it falls or is knocked off into a collection tray, leaving a hole where the ice was clinging to the rod.
Because there needs to be room for expansion in order to allow the impurities to fall to the bottom of the freezing water, only ice of a certain larger size can be made this way, and what usually happens is the ice gets cut up into smaller chunks.
[Here’s a good tutorial on how to make clear ice that demonstrates the process.](https://www.youtube.com/watch?v=J-flw623kjM)
Latest Answers