Talk:Color of water

Misconceptions everywhere!

From talking to many people I find that very few know that water is a blue-colored chemical. Even science teachers don't know this, and science textbooks never mention it. Billions of people look right at blue oceans all their lives, but without knowing... that water is a blue substance?! Bizarre! How did this situation come about? --Wjbeaty 08:08, 4 September 2007 (UTC)

I visited Crater Lake, which is famous for its intense blue color, and noticed that in their brochure, and in their mounted plaques, their explanation of color does not mention that water is itself a blue substance. They do explain how blue dyes work: absorbing the red/green frequencies. But they avoid saying that water itself is like a blue dye. When I asked one of their staff about this, she became angry over the topic. She stated that nowhere in her training or reading or in literature provided to staff, does any author ever mention that water is a blue-colored substance. (Exactly the problem!) But she concludes that water is transparant, and that I was lying or perhaps insane, rather than accepting that water could be blue, or suspecting that a bizarre problem exists in elementary textbooks' explanation of blue lakes and oceans.

So I guess that the general public thinks that science is determined by voting. If thousands of references say that water is a transparent substance, then any few people who say that water is a blue substance... are wrong by definition? The majority rules, and massed authority must be correct. And that's probably the cause of this strange problem. R. Feynman must have been wrong when he insisted that science was all about distrust of authority. Galileo had to be wrong, since he was just one person. "And yet it moves.")--Wjbeaty 08:08, 4 September 2007 (UTC)

The general public thinks?! --Quiddity 17:41, 4 September 2007 (UTC)

Well if that's the case, what is the evidence that you can show to the genral public to prove that a water molecule is slightly blue? After all they drink it and is seems colorless! —Preceding unsigned comment added by 212.118.23.78 (talk) 14:47, 24 March 2008 (UTC)

The term 'transparent' is a very relative term, transparency is frequency (color) dependent. All substances absorb light in some region of the spectrum. Water is no exception, but its absorption is very slight in the red end, so slight that thick layers of water are required to observe it with the naked eye. There really is no contradiction of stating that water is transparent and that it has blue color. Transparency really only means that absorption is so slight that one can still see through the material. I hope the article makes this clearer now with the new section on intrinsic color. Kbrose (talk) 03:22, 28 March 2009 (UTC)

Old Black Water

The article contains the following statement:

A few tens of meters of water will absorb all light, so without scattering, all bodies of water would appear black.

But this clearly cannot be true because the Super-Kamiokande neutrino detector uses an active volume of (ordinary, not heavy) water that is "33.8 m in diameter and 36.2 m in height" and light can be seen from the center of that cylinder so at least ~16 metres away (and I think the detection scheme expects lightto make it all the way across the volume of the active cylinder).

Does anybody know the actual attenuation of visible light by ultra-pure water?

Atlant 17:28, 8 November 2007 (UTC)

Merge proposal

Blue ice (glacial) seems an obvious candidate to become a section of this article, which as it stands does not talk about solid water at all.

--207.176.159.90 (talk) 23:26, 25 March 2008 (UTC)

It's ice, not water. If anything it should be merged with something about ice. I don't support a merger though of the page. Kevin Rutherford 00:43, 9 May 2008 (UTC)

With KR o this one -- keep it simple and findable, the blue ice I mean. Julia Rossi (talk) 01:27, 8 August 2008 (UTC)

Blue ice should not be merged. It has industrial uses that extend the definition beyond "color of water." —Preceding unsigned comment added by 144.74.3.21 (talk) 17:44, 14 August 2008 (UTC)

I boldly added such a section, rather than merging the two articles, before I read this discussion. In general, WP editing is not dependent on achieving a clear consensus. Note that the term "water" is orthogonal to (independent of) the state of the water. Also note that discussions of the color properties of water vapor and the triple point of water are still missing. David Spector (talk) 16:40, 18 April 2010 (UTC)

Diagram request

I was thinking of the images at http://www.eeb.ucla.edu/test/faculty/nezlin/OceanColor.htm when I added the diagram-request template. Specifically these 2 images (see page for caption/explanations) [1] and [2]. However, I am not an expert in this topic, so remove the template, or point to a better suggestion if you know of one. Thanks :) -- Quiddity (talk) 17:37, 27 July 2008 (UTC)

Other descriptive terms

I don't see the colours "aqua" or "turquoise" in the article but they commonly used in English to describe the greeny-blue thing. Should they be included? Julia Rossi (talk) 01:29, 8 August 2008 (UTC)

In an article this short, it's often best to just be bold. (However, TTT userbox noticed and appreciated. Made me think of Piet Hein's Things Take Time grook (fifth one down, with his illustration even!). :) -- Quiddity 02:16, 8 August 2008 (UTC)

'Grey' ocean...

I always thought the 'grey' ocean was just a description of how it looked on a gloomy cloudy day, not anything specific to the Greek perception of color. —Preceding unsigned comment added by 128.194.103.37 (talk) 02:34, 28 March 2009 (UTC)

I agree. Could be added. This article doesn't have to be limited to physics. David Spector (talk) 16:42, 18 April 2010 (UTC)

Color of Ocean

With reference to section 2, "If the oceans owed their color to the sky, they would be a lighter shade of blue and would be colorless on cloudy days". Has no one ever seen the ocean on a cloudy day? It looks grey / silver! On the right day it can look completely silver giving the effect that a photo is in black and white. I can post some good photos if it helps. The fact that water is inherently blue does not disprove the theory that the sky contributes to the color of oceans. There is no evidence here to suggest the sky does not contribute to the ocean's color, but direct observation supports this theory. The tone of the article is biased towards the "scientific people" feeling good about themselves, being better and more knowledgable than the "bizarre" average person, having developed a perfect theory which proves wrong a so called "common misconception". Instead it should try to be accurate. —Preceding unsigned comment added by 59.154.36.35 (talk) 08:12, 14 April 2009 (UTC)

On a cloudy day, there is simply less light penetrating the ocean waters, not enough light to cause sufficiently visible backscatter back into the atmosphere from water molecules and impurities (which makes the blue color visible when viewing a surface of water rather than viewing water in transmission). With less light most of it will likely be simply absorbed, including any backscatter produced in the water, and therefore, the ocean doesn't show its intrinsic color, but looks neutral (grey) or even black (it doesn't let the light escape). Of course, reflection of light off the surface does occur and does contribute to the visual experience (it does cause the silvery sheen), but this doesn't give any validity to the hypothesis that the blue color of the ocean is from reflection of the extremely weak blue of the sky. That said, the quoted sentence is indeed a bit odd ('... would be colorless on cloudy days.') as that is what seems possible. Scientific people should indeed feel good about using measurement and logic, rather than jumping from observations to conclusions without scrutiny, as in your 'perfect theory' scenario. The article, however, was hardly written by scientists. Kbrose (talk) 07:19, 15 April 2009 (UTC)

Your explanation sounds more like speculation regarding something that isn't properly understood rather than science. I would have thought a logical and valid conclusion to the observations "ocean is grey when sky is grey" and "ocean is blue when sky is blue" would be that the sky has a significant contribution to the colour of the ocean. Instead you think from these observations that it's logical to conclude that the colour of water is the main contributor of ocean colour? This is nothing to do with whether water is inherently blue, but rather what factors signicantly contribute to the colour of ocean, which may or may not be the inherent colour of water and may or may not be the sky. Observation suggests the latter. —Preceding unsigned comment added by 59.154.36.46 (talk) 05:05, 27 May 2009 (UTC)

I've just been reading about this on various websites, and though it is agreed that water is naturally blue in colour, other things - the colour of the sky, and particles within the water - have a major effect as well. As with 59.154.36.35, my personal experience is that the sea changes between blue and grey depending on the weather. According to http://starryskies.com/articles/dln/3-98/water.html: "The ocean often usually looks gray on a stormy day. Partly, that's reflected gray sky - but it's also because clouds filter out a lot of the sun's red light before it ever reaches the water." This article should feature this fact more prominently, as it is the article is wrong because it goes directly against many people's personal observations. 213.107.75.169 (talk) 17:20, 2 August 2009 (UTC)

That starryskies link gives a very simplistic explanation for the Black Sea. See our section on the name at Black Sea#Modern names.

Also, bear in mind that personal observation does not always match objective reality. See Same color illusion and related Color vision articles. -- Quiddity (talk) 20:39, 4 August 2009 (UTC)

I also agree that these statements contradict everyday experience. It is also unclear exactly what "colorless" means. I have flagged them as needing citation/clarification. 86.136.194.38 (talk) 20:13, 3 November 2009 (UTC).

There is too much speculation in this talk section. References are needed per WP policy. We don't vote on science; we cite research results. David Spector (talk) 16:48, 18 April 2010 (UTC)

Colours in general

The science in the general discussion is wrong. The colour of a body of water that we see is due to light emitted by that body. Ignoring reflection, this has two possible origins

• Rayleigh scattering This is caused by scattering from molecules. Intensity is proportional to the fourth power of the incident light frequency, so blue is scattered more strongly than red. For example, see Blue Grotto (Capri)
• Tyndall scattering This is caused by scattering from particles. Intensity depends on particle size. Rough sea water is green due to the presense of a suspension of fine sand particles. In some alpine lakes the green colour is due to suspeded algae or bacteria.

In addition some of the scattered light may be absorbed by the fourth overtone of the O-H stretching vibration which will contribute to the blue colour. The clearer and deeper the water the more intense the blue colour for this reason. Petergans (talk) 11:14, 15 December 2009 (UTC)

Places having blue water

What's the purpose of this section, which is marked as requiring expansion? Since the article establishes that water is blue, anywhere that has water, has blue water. It seems like an invitation for a list extolling the virtues of editors' favourite travel destinations. AlmostReadytoFly (talk) 08:26, 27 April 2010 (UTC)

Agreed, removed.

The Blue Grotto (Capri) is no longer mentioned, though per the thread above this, perhaps it could be worked in as an example elsewhere. -- Quiddity (talk) 19:49, 27 April 2010 (UTC)

I disagree. While water may be blue, the North Atlantic, the Gulf of Mexico along the US coast, and the North Sea are almost always green, even on sunny days. Lakes in parts of Texas and Georgia can even be rather red because of suspended clay or a clay bed. And the "Blue Danube" almost never is. The Baltic and the Caribbean, however, are truly blue and there are places in the world where the blue color is especially vivid, such as the Yucatan coast. --Janko (talk) 10:45, 17 March 2011 (UTC)

Completely unnecessary citation needed

Do we really need a [citation needed on] "If the oceans owed their color to the sky, they would be a lighter shade of blue, and would not appear blue on overcast days." Shouldn't it be common knowledge that every reasonable person has that the sky is not dark blue in daylight and appears white or gray when overcast? 75.66.80.108 (talk) 18:31, 29 May 2010 (UTC)

Possible incorrect usage of picture

Is this correct? I believe the reason why water is blue in a swimming pool is due to chlorine. The volume of a water in a swimming pool should not be enough to turn water blue. Any thoughts? Valoem ^talk 18:28, 15 March 2011 (UTC)

it could also be due to the color of the pool. Some pools are panted blue on the bottom. — Preceding unsigned comment added by Tideflat (talk • contribs) 00:42, 18 March 2011 (UTC)

The pool in the photo is a diving pool, about 4 meters deep. I can attest that when the pool is drained, the sides are white. water is blue because water is blue Incredio (talk) 18:57, 20 March 2011 (UTC)

Actually, water in a pool is not enough to turn blue it is due to chlorine. You can see the evidence right from the photo. Water in the dish is clearly NOT enough to water blue, in fact a bath tub water remains clear (you can test it yourself). On wikipedia you need a reliable source before you can post uncertain information. Valoem ^talk 17:23, 28 March 2011 (UTC)

In context, I think our article made it reasonably clear that the colour of pool water might be affected by chlorine or other impurities. Perhaps the caption could also mention this explicitly, although its main focus should remain on the general concept that degree of colour seen depends on the amount of water. Pure water is not common in large quantities, so if pool water, sea water, etc differ in colour, this is still a reasonable thing to cover here. I agree the article is light on sources in this section; do you know of any? --Avenue (talk) 03:58, 3 April 2011 (UTC)

This picture needs to be removed, it is very misleading. Water is blue, but it's not that blue. Looking through one inch of water in this picture at the white tile, the water looks very blue. Yet when when through one inch of water in a drinking glass, its blue color is indiscernible (as demonstrated by the earlier photo with the strawberry splashing). These two photos seem to contradict each other. 129.63.129.196 (talk) 20:13, 7 December 2012 (UTC)

One would imagine that the water in the bucket was scooped up from the pool. If so, the difference in colour cannot be explained by chlorine or anything else in the water. The depth of water in the pool could obviously explain the difference, but if colour depends on depth then why is the water not colourless at the edge of the pool, where one is looking through only an inch or two? A very brief experiment suggests that this may be a counter-intuitive property of coloured liquids in general. This topic needs further research. 86.176.212.216 (talk) 03:37, 26 December 2012 (UTC)

Some addition to this topic: I have made colorimetric calculations (using the CIE 1931 2-deg standard observer and sRGB) of the colour of water by using the absorption coefficients by Pope & Fry 1997/Kou et al. 1993 (the same data used for the plot), and found that the colour of a white surface (e.g. a white tiled pool floor) really appears pale blue, and the blue tint should be clearly visible even at 1 metre or below. At 4 m the color of light after two-way tranmission (i.e. down to the assumed white floor and back to the observer) would result in sRGB components of approx. R,G,B = 0.22, 0.83, 0,98 (or x,y = 0.220, 0.290). The chromaticity would even be outside the SRGB gamut for a pool as deep as only 5 metres! Somewhat unclear is the origin of the blue tint near the surface; maybe it is due to back reflection of light from the floor by the water surface. I can upload colour gradients (as PNG image) with the corresponding x,y,Y colorimetry data included as table in the description page. However, I am not sure whether this might violate the OR restrictions.--SiriusB (talk) 08:48, 28 July 2013 (UTC)

It is counter intuitive that the colour is the same intensity all the way up the side of the pool. But we are not looking at light which has travelled only an inch or two down and reflected diffusely off the tiles. Unless one looks almost parallel to the surface, the light ones sees has been totally internally relected (TIR) every time it meets a tile on the side of the pool. In effect the sides act like mirror tiles. The light has come by TIR from the bottom of the pool. It may have travelled a greater distance through the water than light which entered the camera when looking vertically down. In that case the colour would be more intense the higher the point it appears to have come from. So I am perfectly happy with this photograph.PhysicsW (talk) 20:26, 1 December 2014 (UTC)

The blue of swimming pools is too intense to be due to the water's natural color. It is not due to chlorine, which is a yellow-green gas. (Even bleach, that contains much more dissoved chlorine than would be allowed in any pool, is yellowish, not bluish.) I bet that swimming pools are blue for the same reason that Fanta is orange: because most swimming pool chemicals (the stuff that people commonly call "chlorine") include some blue dye, to yield the blue color that people expect from sea and large clean lakes. --Jorge Stolfi (talk) 21:04, 27 September 2016 (UTC)

Kbrose removed an image that I had added...

Kbrose removed an image that I had added, saying "rv, short lede is poor and water image does not show colorless water, too much color in background". So I am asking what should be in the background? I don't see anyway for there not to have color in the background. Even if it is white it will still be a color. Tideflat (talk) 20:32, 19 March 2011 (UTC)

Do to the lack of response, may I add the image back? Tideflat (talk) 16:28, 2 April 2011 (UTC)

I don't agree that "white is still a colour" in the sense meant here. A white background is neutrally coloured and would show any colour change well. So I think the image could be improved. Having said that, the image you added does show there is little colour change, so I think it would make sense to retain it until a better picture can be found. --Avenue (talk) 23:30, 2 April 2011 (UTC)

Then how is this one instead? It has a white background. Tideflat (talk) 01:04, 3 April 2011 (UTC)

A suggestion for a replacement for the image

It's okay, seems a bit over-manipulated to me though. --Avenue (talk) 02:08, 3 April 2011 (UTC)

Here is a different one, The only problem I can see with it is that the Strawberry might distract.

— Preceding unsigned comment added by Tideflat (talk • contribs) 16:39, 3 April 2011 (UTC)

Or perhaps it piques the reader's interest. I like it, others may not. --Avenue (talk) 22:37, 5 April 2011 (UTC)

Then I will use it. Tideflat (talk) 23:22, 5 April 2011 (UTC)

This article contradicts itself!!!

In section 'Color of lakes and oceans' -

"It is a common misconception that in large bodies, such as the oceans, the water's color is blue due to the reflections from the sky on its surface. Reflection of light off the surface of water only contributes significantly when the water surface is extremely still etc."

So here it clearly says that the color of oceans are not determined by the color of the sky, since it is next to impossible for the ocean to be 'extremely still'. But at the end of the section:

"The surfaces of seas and lakes often reflect blue skylight, making them appear bluer."

Amazing. One of these statements obviously need to be removed.

The first quote could perhaps be rephrased a little, but they don't contract one another. The first says that reflection contributes when the water surface is still, and the second says that reflected light often makes water appear bluer. Player 03 (talk) 02:37, 29 November 2011 (UTC)

OR in swimming pool

Okay, regarding this material, I'll be more specific.

• "the water in a swimming pool also appears blue even when the optical path length through the water to the white sides is mere millimeters"

The optical path length hasn't been measured in this setup.

• "evidently reflection at the air-water interface shifts the source of illumination to light that has traversed a large distance through water"

That's not evident; in fact, it doesn't make sense geometrically.

• "as demonstrated with a floating white bucket with water in it"

This is a synthesis of multiple observations made to argue a point.

• "Popular belief is that the blue color must be intensified by the presence of chlorine"

There is no evidence that this is a popular belief.

• "The lack of blue color of the water in the bucket could be hypothesized to be due to the catalytic destruction of the popularly-believed chlorine coloring agent by the plastic of the bucket"

This is speculation for the sake of argument.

• "more conventionally the explanation relies on the greater optical path length for the deep swimming pool as compared with the shallower bucket"

This isn't a novel interpretation, but it does conflict with the "reflection" argument above. Melchoir (talk) 06:20, 5 October 2011 (UTC)

In this edit, I've removed the above snippets and added sources for the rest. Melchoir (talk) 07:05, 5 October 2011 (UTC)

The above changes are reasonable. Incredio (talk) 02:19, 6 October 2011 (UTC)

Unexplained calculations

Sorry if this is a silly question, but I feel it needs explanation. In the section "Intrinsic color", the "harmonic" v₁ + 3v₃ = 14,318 cm⁻¹ is the one that is said to be responsible for the behaviour of water molecules in the visible spectrum when v₁ = 3650 cm⁻¹ and v₃ = 3755 cm⁻¹. However, simple calculation shows that the sum is 14915 cm^-1, which corresponds to a wavelength of around 670 nm. The difference appears to be significant on the spectral scale. I checked the reference cited, but the authors of the paper have not explained the anomaly. Nowhere have I been able to locate any justification for such a glaring approximation. Now, although 670 nm still is within the range of red spectrum, it certainly isn't "at the edge" of it, as claimed in the paper. Am I missing something? Why would there be such an error? Does it make a difference? Should other sources be cited? Knaveknight (talk) 08:22, 7 November 2015 (UTC)

No mention of Alpine Lakes and Creeks water looking Green.

I don't dispute that many lakes, rivers, etc. look green from Biological bodies but that particular color green is entirely different from the Emeral/Jade green viewed at many alpine lakes, rivers. Of which, where I grew up, was always attributed to the dissolved Gneiss in the water. And there isn't much Biological to make the water green at altitude. Moreover, they should appear reddish brown from the tannins if anything. For example, zooming-in to many of the Cascades alpine watersheds closely and they do indeed appear green, rather than the blue initially. 80.5.219.60 (talk) 17:58, 26 January 2016 (UTC)

Too unscientific

The whole article reads like a collection of layman's guesses. See for example the section on swimming pool colors, that ignores the fact that the pool chemical formulas very likely include a blue dye. The article needs a thorough review by real experts... --Jorge Stolfi (talk) 21:09, 27 September 2016 (UTC)

• Agree.

While I know the article Electromagnetic absorption by water exists and caters for the more scientific presentation, this article could do with a little more substance, though with focus on the visible portion of the spectrum ("visible portion of the spectrum" basically means "color").

I suggesting including an image such as this: http://www1.lsbu.ac.uk/water/images/water_spectrum_2.gif but cropped down to the visible. In that image, the visible region is very nicely annotated by colors. Converting absorbance to units of "per metre" would make it much more easily understood, in particular with respect to why looking through 10cm appears colourless, 10m appears very blue, and 100m black. --SmokeyJoe (talk) 00:08, 11 October 2016 (UTC)

Color or colour?

In other words, is this American English Wiki or English wiki? RoclorD (talk) 20:19, 7 December 2017 (UTC)

Either. Per WP:TITLEVAR, we don't currently change the title once the article is created if it doesn't matter. Erik Humphrey (talk) 07:40, 26 January 2021 (UTC)