My experience is exactly the opposite. I have an in-ground pool with white plaster over gunnite. As a result, everybody I know who has a pool calls me when they decide to do some deep cleaning. So I’ve seen a couple dozen other pools without (all of the) water and the plaster has been white in every one of them.
I’ve seen hotel pools that were tiled, all the way to the bottom, and the tiles were usually not white. The ones that stick out in my mind were mosaic tiles with random light blue and dark blue patterns.
I know it’s theoretically possible to color plaster, just as you can color concrete, but I’ve never seen it done.
One thing I can say is that in the South, where it’s hot 10 months out of the year, algae breeds FAST, and if you don’t notice the first spot and get some algaecide in there really quick, you’ll end up with a green pool. If you had colored plaster, you might not see it in time.
Things may be different in cooler climates where algae isn’t a much of a problem.
Liquid ammonia containing various alkali metals are also colored. I’ve never had to use the conditions, but I believe that sodium in ammonia gives a blue color.
Yeah, after I posted I thought that maybe oxygen and ozone do coexist, maybe in an equilibrium state. I can’t tell if pure oxygen, if it’s even obtainable separate from the small quantity of ozone, has a colour. I’ll wait for the chemists.
Ozone is made n the upper atmosphere by pretty high energy UV rays. These rays don’t exist on the surface in high quantities and they certainly don’t exist in laboratories indoors. I’m not certain exactly how ozone is made as a pollutant at the surface, but I’m guessing it’s not the sort of thing that happens spontaneously in any significant amount.
Oxygen is definitely blue on it’s own. In almost all cases, visible color is a result of electronic transitions and oxygen has a pretty unusual electronic ground state. The electrons in it’s ground state are not paired. There is an electronic state available where the electrons are paired, and if I had to guess, this transition would probable fall into thew visible range.
I realize the beginning of this thread is seven years old, but Fighting Ignorance is timeless.
Here’s a reprint of an article explaining the blueness of water. Although the “reflects the sky” explanation is common, it’s not correct. the blue of pure water is different from the blue of the sky (which is largely due to Rayleigh scattering, although there are a few other effects)
https://www.dartmouth.edu/~etrnsfer/water.htm
as for liquid hydrogen, Dewar, in his original 1899 article, calls it “colorless”, but subsequent work shows that there are absorption bands in liquid hydrogen. The thing is, I can’t pull them up on a quick search.
Most of the blue color of large bodies of water is due to reflection from the sky. Yes, there are some places and times when the sky mostly isn’t blue, but in those circumstances, the water isn’t very blue, either.
Chronos, the post before yours by CalMeacham cites a paper in the Journal of Chemical Education that explicitly contradicts the idea that the blue of water is reflection from the sky, including several experimental results, spectograms and a theoretical model. You’ll need at least an equally compelling citation to support your bare assertion.
While the experiment needs to be verified a group recently claimed to successfully create metallic hydrogen and they described it as a reddish silver speck.
As there have been claims before that did not stand up to peer review or replication I would advise caution in taking this as a definitive at this time.
Here is a graph that better shows the weak absorption of visible light in pure water.
I should note that this absorption effect is tiny in the visual band.
To avoid making people do math here is a simplified explanation.
It is actually a side effect of water absorbing infrared light which causes stretching of the Oxygen and Hydrogen bonds. The third harmonic of this frequency lays within the red area of the visible spectrum.
I see Lake Erie twice every day on my commute. It doesn’t usually look blue, in accordance with the fact that skies around here don’t usually look blue, either.
Hmmp. I thought color was an interactive thing, unless the whatever radiates photons.
Of course, if something glows a certain color, that might just be what we sense of it. It’s visual “sweat” so to speak. The thing itself could be a completely different “color.”
Isn’t vision kind of like smell? In that what we smell, isn’t the thing itself, we smell whatever the thing sheds, that can enter our nasal passages.
The color of lake water is dependent not only on the H20 components but what is also in it. As water is the universal solvent it is very rarely even close to pure.
Crater lake as a random example is far higher in purity than the great lakes and this color is more typical of the pure water color (although far from exact)
XKCD has a strip discussing why the sky is blue – “because air is blue.” So even stuff that normally looks clear, like air or water, will show a color if you look through enough of it?
