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?
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Gotta say, It’s not backed by science or anything. I’m just a bartender. But I’ve been using ice molds for ages and I’ve since learned that if you pour HOT water into it and put it directly in the freezer, it freezes clear. Where as COLD water always has a cloudy look. Someone could probably explain it. But I know this to be true.
Hey, it’s about time I can answer something on here. Most of the ice cubes with holes in the middle are made by industrial processes rather than commercial processes. At those ice plants, they use tubes inside a shell that is vertical (AKA, a vertical shell and tube heat exchanger) with a spinning blade at the bottom. The refrigerant flows (normally Anhydrous Ammonia) through the tubes and water is sprayed from the top. The water is frozen to the thickness of the customer specification, and then the tubes use a defrost cycle to drop the ice down the tubes, hitting the spinning blade at the bottom cutting it the desired length. This happens at a fairly rapid pace but also they will have several of these in a line going through different stages at a time. Then, the ice hits a conveyer belt and is sent to packaging.
Source: I am an Ammonia Refrigeration service technician.
The cloudiness in homemade ice cubes is from gas bubbles forced out of solution as the water freezes. Commercial ice makers probably preheat the intake water (or use a hot-water feed) which will degas the water ahead of time and give ice without bubbles.
Most ice bags have ‘tubed and cubed’ shaped ice.
Tubed has a larger surface area and makes your drink cold faster.
Cubed has less surface area so makes it cold longer.
You need both to have a drink that is cold for a quick time and for a long time.
This reminds me of how inuit catch polar bears. First, they cut a hole in the ice. Then, they fill the hole with peas. Finally, when the polar bear comes to take a pea, they kick him in the ice hole.
Here’s a YouTube short video of those things at work:
# [This is how ice making machines work](https://youtube.com/shorts/xbH2XH5Pxmo?feature=share)
The freezing cold refrigerant is run through a bunch of cold “fingers” on which the ice forms. They reverse the operation briefly to get the ice to melt off of the fingers.
The ice is much more clear because the ice is freezing inside-out. When ice forms, all of the dissolved gases and minerals get pushed away from the growing ice crystal. Your typical ice cube frozen in your freezer freezes outside-in, and this pushes all of the impurities and dissolved air into the middle, causing there to be a cloudy patch in the middle of the ice cube, but when ice is formed on these cold finger style ice makers, the ice freezes inside out, so the inside is really clear, and the impurities are pushed into the surrounding water. When the water basin is lowered away from the cold finger, all you’re left with is clear ice.
Any cloudiness or inclusions in this kind of ice only form because the freezing is happening so fast that impurities get trapped at the boundaries between individual ice crystals.
(Mono-directional freezing is how fancy bars make large clear ice cubes as well. They have gadgets that let the ice freeze top-down so all the impurities and dissolved air gets pushed out the bottom.)
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