Sure, there’s some romance from hand-harvested ice, but you can’t beat the price and purity of ice from a freezer.
(The freezer, of course, has nothing to do with this - it's the water you're putting into it that's impure.)
> Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. [1]
Other sources list carbon dioxide, oxygen, and nitrogen as impurities that can cause corrosion in pipes [2], or can form bubbles in systems where there are major changes in pressure or temperature, blocking pumps, fine tubing, filters, etc. [3]
So it’s a bit context dependent, but there are situations where it is totally reasonable to view dissolved gases in water as an impurity. And this context - the discussion of what makes ice clear or cloudy - is one of them.
How can you claim so confidently that “no one thought” something, or that the parent is “using a word much differently than basically anyone else”? If you honestly think that you speak for all 1.35 billion English speakers in the world - or even all the people reading this thread - the best I can say is speak for yourself.
[1] https://en.m.wikipedia.org/wiki/Water_purification
[2] https://www.watertechnologies.com/handbook/chapter-01-water-...
> The most common impurities found in tap water include lime (also known as limescale), calcium, fluoride, nitrates, magnesium and certain other organic elements that are practically impossible to remove with regular filtration methods. So, when water freezes, the impurities that were evenly distributed in the water, tend to congregate near the middle, making ice cubes the whitest at their center. [1]
> But the reality is, most of the “impurities” found in your freezer ice cube are more likely nothing more than the minerals present in your tap water. Tap water commonly contains minerals such as: Calcium, Magnesium, Potassium [2]
Do you have a citation to back up the claim that it's only air bubbles?
[1] https://www.scienceabc.com/eyeopeners/why-are-some-ice-cubes...
[2] https://blockice.com/blog/whats-the-science-behind-clear-ice...
As evidence that directional freezing can filter out impurities other than air, I would point out that the directional freezing process is an effective enough filtration method to filter salt out of sea water in sea ice. [1] So my assumption is that those other minerals commonly found in water (lime, calcium, fluoride, magnesium, etc) are also being filtered out in the process - and it certainly seems plausible to me that filtering those out contributes to the clarity of the resulting ice.
So my intuitive understanding, along with what I could learn with a bit of googling, is that there are a number of impurities which can make ice appear cloudy including (but not limited to) dissolved air. A number of people here seem to be adamant that it's just air bubbles, so I'd honestly like to know why they believe that to be true (e.g. sources, some clear explanation, etc)? So far the only justification I've seen is "because directional freezing works" - but as explained above I really don't see that as being a sufficient justification since it filters out a number of impurities other than air.