Glass is green

[5614]

If you have a sheet of glass (more than a few mm thick) and you look at it from the side then it looks like (from the side) the side of the glass is green.

 

for example, there were some glass shelves (quite thick) in this shop i was in. from the side they looked a bit green. not the main thing.. just the side part.

 

like here:

 

and here:

 

why does this 'green glass' effect happen?

[Cap'n Refsmmat]

I think it's something that the manufacturer puts on to make it look better.

[5614]

I think it's something that the manufacturer puts on to make it look better.

REALLY? well there goes my complicated light diffraction answer i was expecting? can anyone varify what cap'n said?

 

(just you said "i think")

[bloodhound]

i think it may be due to the fact that the manufacturer has filed the shard edges

[maverick88]

Had you ground the glass you would have seen the difference. If glass was green you wouldn't have seen through it like you can't see through the side like is presented it the picture. But as you know sometimes vert wide windows are produced and still we can see through

[swansont]

Consumer grade soda-lime-silicate glass absorbs and/or scatters light just a little unevenly across the visible spectrum, so you lose some red and blue relative to the green.

 

You can also see this effect in a room with mirrors on both walls (like a large public restroom/lavatory) When you look into the mirror and see the multiple reflections, they will often look increasingly green.

[5614]

Had you ground the glass you would have seen the difference

 

firstly i know glass isnt actually green, it just from the side the side part looked it and it seemed a reasonable title.

 

(about the quote) are you saying that side appears green because it had been grounded?

 

basically what im asking is what causes the side of a pane of glass appear green?

 

do you know what i mean? the 2nd pic in my original post shows it quite well.

[swansont]

basically what im asking is what causes the side of a pane of glass appear green?

 

For light to have come out the edge, it basically has to have entered through another edge* so you get total internal reflection. So it travels a large distance through the glass, which is acting like a waveguide. Absorption.

 

*it's possible a small amount scatters off of some impurity, or some other medium on the surface allows coupling into the glass at some angle.

[ecoli]

For light to have come out the edge' date=' it basically has to have entered through another edge* so you get total internal reflection. So it travels a large distance through the glass, which is acting like a waveguide. Absorption.

 

*it's possible a small amount scatters off of some impurity, or some other medium on the surface allows coupling into the glass at some angle.[/quote']

 

 

This sounds resonable to me. Light enters at an akward angle causing green light to be reflected off of it. Does this make any sense?

[swansont]

This sounds resonable to me. Light enters at an akward angle causing green light to be reflected off of it. Does this make any sense?

 

I don't think it's reflection. It's light that enters through other edges.

[Martin]

another question about light

bare earth can be fairly light colored-----dusty gray brown

and then when you wet it, it makes dark patches

 

why does putting water (transparent) on soil (and some other materials)

have the effect of darkening it?

[swansont]

another question about light

bare earth can be fairly light colored-----dusty gray brown

and then when you wet it' date=' it makes dark patches

 

why does putting water (transparent) on soil (and some other materials)

have the effect of darkening it?[/quote']

 

One effect is that you've changed the reflection properties. Instead of diffuse reflection, it's specular (i.e. mirror-like). (That's why, when driving on rainy nights, it looks darker.)

 

There is probably more to it than that, though.

[ecoli]

I don't think it's reflection. It's light that enters through other edges.

 

No, I meant other wave lengths are absorbed and only green light is reflected out.

[swansont]

No, I meant other wave lengths are absorbed and only green light is reflected out.

 

I'm talking about transmission, not reflection. I don't think reflection is involved.

[coquina]

I tried to respond earlier, and my reply went to thread purgatory.

 

Tektites are naturally occurring glass from impact melt - they are often green.

 

Also - I live near Jamestown, VA, where they have recreated the first industry in Colonial times, which was a glass works. The glass pieces which found at the site of the old factory were green, as is the glass that is manufactured there now.

 

I think that modern manufacturing methods take the majority of the green color out, but when you look through the edges, because you are looking through such a thick surface, you see a greater number of residual particles, which makes it look green.

 

If you google for images of "optically clear glass" you can see some examples where the edges are shown and they are transparent.

 

Another factor might be that the glass used to make thicker shelves has probably been tempered so it will crumble rather than shatter. There are 2 methods of tempering - one involves annealing it with heat to make it harder, the other, less expensive method which is probably the one used on shelves and such is to coat the front and back surfaces with a clear substance. There might be enough color in the substance that is appears colored when you look through the edge and see the back side of it.

[ecoli]

Do tektites affect the way light is absorbed/reflected?

[coquina]

They have a lot of impurities and incomplete melting - look here:

http://images.google.com/images?q=tektites&hl=en&btnG=Google+Search