Why Does Ice Appear White?

[Sam Ku.D]

When we look into the ice cubes, there is a white colored part in the middle(inside at the center). I google searched and most of them say it's the colour of the gases trapped inside when it froze.
But there are no white coloured gases inside. is there? let's take oxygen, its a colourless gas. CO₂ , colourless... etc.
So why is ice white?? is it due to the impurities inside it?

 

[256bits]

Scattered reflection from the tiny gas bubbles.

 

[Sam Ku.D]

Scattered reflection from the tiny gas bubbles.

why white??

 

[ZapperZ]

why white??

Look at it using red light. Do you think it is still "white"?

Zz.

 

[adjacent]

Look at it using red light. Do you think it is still "white"?

Zz.

So the sunlight is scattered?

 

[UltrafastPED]

The tiny bubbles are "white" for the same reason as sugar or salt granules - scattering of the sun/room light.

Since the light contains all of the visible colors of the spectrum this "optical mixing" generates white light.

Larger grains of salt or sugar, or larger bubbles are transparent.

 

[dauto]

Which is also the same reason a bubble bath is white, and a cloud is white, and snow is white, etc...

 

[adjacent]

Which is also the same reason a bubble bath is white, and a cloud is white, and snow is white, etc...

That answers my childhood question

 

[Sam Ku.D]

yeaa! now i know! soo if we boil and remove the gases inside, will the ice be transparent?

 

[PhysicoRaj]

You boil ice and it still remains ice?

 

[Sam Ku.D]

You boil ice and it still remains ice?

nah! its not like that! boiled water! :3 if we boil water and then freeze it, will it be transparent?

 

[PhysicoRaj]

Nice to try! I never tried this so you might. :)

 

[OmCheeto]

yeaa! now i know! soo if we boil and remove the gases inside, will the ice be transparent?

It may take a few tries, according to these guys.

 

[Borek]

if we boil water and then freeze it, will it be transparent?

It calls for an experiment, what are you waiting for?

 

[adjacent]

nah! its not like that! boiled water! :3 if we boil water and then freeze it, will it be transparent?

I think you will need to boil it and freeze it in a vacuum to ensure that there are no gases.

 

[Sam Ku.D]

I think you will need to boil it and freeze it in a vacuum to ensure that there are no gases.

we can keep it in a place where there are no soluble gases?

 

[adjacent]

we can keep it in a place where there are no soluble gases?

Removing soluble gases are in my opinion, more difficult than making the place a vacuum.

 

[OmCheeto]

Removing soluble gases are in my opinion, more difficult than making the place a vacuum.

Creating a vacuum is easy. Proving you've created a vacuum, is hard.

It calls for an experiment, what are you waiting for?

I'm up for it.

Crystal clear ice images in x hours!

0 < x < ∞

 

[russ_watters]

nah! its not like that! boiled water! :3 if we boil water and then freeze it, will it be transparent?

Ever see a hockey rink...?

 

[mrspeedybob]

Removing soluble gases are in my opinion, more difficult than making the place a vacuum.

If you use a vacuum the water will boil and freeze at the same time, you will end up with bubbles of water vapor. Better to start in an environment pressurized with only water vapor. Also, If you cool the sample too rapidly the outside surface will freeze before the center, thus trapping the water in the center and creating stress as the center freezes and tries to expand. This could result in stress fractures that would scatter light just like the bubbles did and cause a white appearance.

 

[OmCheeto]

...This could result in stress fractures that would scatter light just like the bubbles did and cause a white appearance.

I think I just witnessed that!

Images in x - y hours...

While checking my vacuumed water, I noticed that the core had not yet frozen.

 

[OmCheeto]

Creating a vacuum is easy. Proving you've created a vacuum, is hard.
...

Actually, I've just discovered, that it is not that difficult, to prove you have a vacuum.

Eureka!

 

[OmCheeto]

Can't wait! Can't wait! Must publish! Must publish!

Oh yeah...

time for a cigarette...

 

[PhysicoRaj]

That's a beauty OmCheeto! Even I tried it but could not get a perfect transparent crystal. I get that central mystical froth inside, and I believe it jutted out of the surface a few minutes later.. I wonder what that was.

 

[Sam Ku.D]

so it really is possible! making transparent ice! :D i'll also try it in my way!
more amount of impurities means less transparent? huh?

 

[OmCheeto]

That's a beauty OmCheeto! Even I tried it but could not get a perfect transparent crystal.

I tried 3 different methods.
1. Tap water under a vacuum.
2. Previously frozen water at atmospheric pressure
3. Previously boiled water at atmospheric pressure

All three looked pretty much the same when they froze.
Except that the vacuum sample was inside a 10cc hypodermic syringe, positioned vertically.

If you use a vacuum the water will boil and freeze at the same time, you will end up with bubbles of water vapor.

Although water vapor bubbles formed, they didn't form everywhere. The black sections of the lower half, perimeter section, of my image, was crystal clear.

Better to start in an environment pressurized with only water vapor. Also, If you cool the sample too rapidly the outside surface will freeze before the center, thus trapping the water in the center and creating stress as the center freezes and tries to expand. This could result in stress fractures that would scatter light just like the bubbles did and cause a white appearance.

bolding mine
This is what I observed in all 3 sets of ice cubes.

It's not very visible, but at the bottom of my image, is a christmas tree shaped set of white fractures.
The central tube looking thing was caused by me taking the syringe out before the sample had frozen solid.

And the reason I knew I had a pretty good vacuum?
When I removed the syringe, I wrapped my hand around it, warming it up, causing a liquid layer to form around the perimeter. I then inverted the syringe, and the ice cylinder slid about an inch, to the end of the syringe. I repeated this with the same result. Since I didn't see any bubbles flowing past the cylinder, I knew there was little gas/vapor in either end.

I believe someone mentioned "vapor pressure" somewhere, so I googled that.
At 10°C, my starting temperature, the vapor pressure would have been about 0.3 psi, I think.

I get that central mystical froth inside, and I believe it jutted out of the surface a few minutes later.. I wonder what that was.

That sounds like an ice-spike.

I have a few feral cats around my house that I try to keep fed and watered. It's a bit difficult in the winter to keep their water from freezing though. One day this January, I found this on my front porch:

I got all excited and took pictures, thinking I'd created the worlds largest ice spike.
I googled it, and found there have been much bigger ones.
Still weird though.

 

[OmCheeto]

so it really is possible! making transparent ice! :D i'll also try it in my way!
more amount of impurities means less transparent? huh?

Well, if you get your water out of a mud puddle, I don't think you are going to get clear ice.

It looks like this guy has figured it out:

https://www.youtube.com/watch?v=o_2TbWEEn9A​

No boiling, no vacuum, no distilling. Just regular tap water.

The trick appears to be to freeze the ice, so that it does not create the stress fractures.

I found another video, but it was 10 minutes long, and presenter was doing a lot of mansplaining.

 

[OmCheeto]

My syringe vacuum ice cylinder maker setup:

I would explain, but I'm late for work.
Hint: There's only 15 cc of water in there.

 

[PhysicoRaj]

It looks like this guy has figured it out:

https://www.youtube.com/watch?v=o_2TbWEEn9A​

No boiling, no vacuum, no distilling. Just regular tap water.

If I get it right, the key things are:
1) Freeze slowly
2) Freeze uniformly
3) Bigger the better ( but doesn't bigger means more stress?)
4) Have patience
I've a little worm in that #3.

 

[mrspeedybob]

If I get it right, the key things are:
1) Freeze slowly
2) Freeze uniformly
3) Bigger the better ( but doesn't bigger means more stress?)
4) Have patience
I've a little worm in that #3.

I think the reasons for #3 are aesthetic. People will notice a large clear ice cube in their drink but may not notice that a small ice cube is clear / different / interesting.