Why Is The Top Of This Drink White? When The Drink Is Black ?

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Offline neilep

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Dear Stoutologists,

(hmm..not too sure if this has already been asked !)


Apparently drinking this stuff is actually medicinal for ewe !

[attachment=6912]

Nice eh ?...looks nice...looks good for ewe...but does it taste nice ?

Anyway, notice how wonderfully light in tone and hue the head of the ready-to-be-imbibed drink is ?


Why's that then ?
..the drink is black !!.the head is white !!..


*sheepy scrapes head and just does not know*....do ewe know ? *le sigh*




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Offline Make it Lady

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Why Is The Top Of This Drink White? When The Drink Is Black ?
« Reply #2 on: 15/02/2009 17:03:32 »
Full of iron and puts hairs on your chest!
Give a man a fire and he is warm for a day, set a man on fire and he is warm for the rest of his life.

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Offline neilep

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Why Is The Top Of This Drink White? When The Drink Is Black ?
« Reply #3 on: 15/02/2009 17:27:22 »
http://www.thenakedscientists.com/forum/index.php?topic=18532.msg209943#msg209943

Thanks RD

Though, I have to say my original question was directed to the specific nature of the patchwork quilt nature of the bubbles only......I think it still needs answering....whereas in this case, it's regarding the difference in the shade of the bubbles against the colour of the actual drink.

Thanks awfully though...I thought I had asked something similar !



« Last Edit: 15/02/2009 18:30:57 by neilep »
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Offline neilep

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Why Is The Top Of This Drink White? When The Drink Is Black ?
« Reply #4 on: 15/02/2009 17:29:11 »
Full of iron and puts hairs on your chest!

Ewe've got hairs on your chest ?  (hmmm..methinks of a few ways ewe can answer that !  [;D])
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Offline techmind

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Why Is The Top Of This Drink White? When The Drink Is Black ?
« Reply #5 on: 15/02/2009 18:01:22 »
Anyway, notice how wonderfully light in tone and hue the head of the ready-to-be-imbibed drink is ?


Why's that then ?
..the drink is black !!.the head is white !!..

I believe the explanation is that the bubbles are very small (made with nitrogen) and so scatter light everywhere hence mostly white.

"Not everything in black and white makes sense"
"It has been said that the primary function of schools is to impart enough facts to make children stop asking questions. Some, with whom the schools do not succeed, become scientists." - Schmidt-Nielsen "Memoirs of a curious scientist"

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Offline neilep

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Why Is The Top Of This Drink White? When The Drink Is Black ?
« Reply #6 on: 16/02/2009 13:26:15 »
Anyway, notice how wonderfully light in tone and hue the head of the ready-to-be-imbibed drink is ?


Why's that then ?
..the drink is black !!.the head is white !!..

I believe the explanation is that the bubbles are very small (made with nitrogen) and so scatter light everywhere hence mostly white.

"Not everything in black and white makes sense"

Thank ewe techmind that is brill !
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Offline Don_1

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Why Is The Top Of This Drink White? When The Drink Is Black ?
« Reply #7 on: 16/02/2009 15:16:43 »
I shall be pleased to carry out a series of experiments to find an answer for this on your behalf. Please send a flagon or three of the said liquid for the purpose.

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Offline RD

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Why Is The Top Of This Drink White? When The Drink Is Black ?
« Reply #8 on: 17/02/2009 13:18:09 »
Quote
9. How does Guinness have a white head when the drink itself is treacly black?
The answer, according to the New Scientist, is down to the bubbles which form the creamy top of the pint. These uniform-sized spherical bubbles, which rise from the black liquid, sit in a dense concentration at the top of the glass. Because they hold only air, they act in an opposite way to a magnifying glass, disseminating light. So light entering the foam is rapidly scattered, some of it finding its way back to the surface, appearing white. It's called Mie Scattering.
http://news.bbc.co.uk/1/hi/uk/2896675.stm
« Last Edit: 17/02/2009 13:20:45 by RD »

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Offline Jolly- Joliver

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Why Is The Top Of This Drink White? When The Drink Is Black ?
« Reply #9 on: 30/03/2011 16:41:09 »
Quote
9. How does Guinness have a white head when the drink itself is treacly black?
The answer, according to the New Scientist, is down to the bubbles which form the creamy top of the pint. These uniform-sized spherical bubbles, which rise from the black liquid, sit in a dense concentration at the top of the glass. Because they hold only air, they act in an opposite way to a magnifying glass, disseminating light. So light entering the foam is rapidly scattered, some of it finding its way back to the surface, appearing white. It's called Mie Scattering.
http://news.bbc.co.uk/1/hi/uk/2896675.stm

The head on a guiness is cream coloured not white, it appears stout produces a bubble which does not reflect light at the same intensity as larger.
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