Naked Science Forum

General Science => General Science => Topic started by: neilep on 15/02/2009 15:46:11

Title: Why is the head on Guinness white when the drink is black?
Post by: neilep on 15/02/2009 15:46:11
Dear Stoutologists,

Apparently drinking this stuff is actually medicinal for ewe !


* guinness_20040423.jpg (60.19 kB . 533x400 - viewed 3224 times)

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 !!..

Tar

Neil
Knows Nowt About Stout
xxxxxxxxxxxxxxxxxxxxxx
Title: Re: Why is the head on Guinness white when the drink is black?
Post by: RD on 15/02/2009 16:01:29
http://www.thenakedscientists.com/forum/index.php?topic=18532.msg209943#msg209943
Title: Re: Why is the head on Guinness white when the drink is black?
Post by: Make it Lady on 15/02/2009 17:03:32
Full of iron and puts hairs on your chest!
Title: Re: Why is the head on Guinness white when the drink is black?
Post by: neilep 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 !



Title: Re: Why is the head on Guinness white when the drink is black?
Post by: neilep 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])
Title: Re: Why is the head on Guinness white when the drink is black?
Post by: techmind 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"
Title: Re: Why is the head on Guinness white when the drink is black?
Post by: neilep 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 !
Title: Re: Why is the head on Guinness white when the drink is black?
Post by: Don_1 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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Title: Re: Why is the head on Guinness white when the drink is black?
Post by: RD 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://www.thenakedscientists.com/forum/index.php?topic=18532.msg209943#msg209943).
http://news.bbc.co.uk/1/hi/uk/2896675.stm
Title: Re: Why is the head on Guinness white when the drink is black?
Post by: Jolly- Joliver 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://www.thenakedscientists.com/forum/index.php?topic=18532.msg209943#msg209943).
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.