Bright and shiny - refractive index question...

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Bright and shiny - refractive index question...

Post by Gfamily » Sun Dec 13, 2020 11:11 pm

A transition from whisky to gin over the last few years makes me ask whether it's an illusion that a glass of gin seems to be much brighter than a glass containing the same amount of water?
Is it optics or anticipation?
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Re: Bright and shiny - refractive index question...

Post by dyqik » Mon Dec 14, 2020 1:18 am

Gfamily wrote:
Sun Dec 13, 2020 11:11 pm
A transition from whisky to gin over the last few years makes me ask whether it's an illusion that a glass of gin seems to be much brighter than a glass containing the same amount of water?
Is it optics or anticipation?
It's quite possible for a few reasons:

1) the refractive index of 40% alcohol in solution is a bit higher than that of plain water, and closer to that of glass, which means less reflection loss at the interfaces from glass to booze, as well as different critical angles and refraction (which is how alcohol content can be measured with a refractometer), which may bring more light through.

2) gin may be slightly bluer than water, making it look a little brighter.

3) quinine is fluorescent, so a g&t (and maybe some gins as well) will fluoresce if there's UV around.

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Re: Bright and shiny - refractive index question...

Post by dyqik » Mon Dec 14, 2020 2:12 am

2oz of Hendricks gin and 2oz of tap water, in identical glasses under the most uniform lighting I could find in our kitchen. And swapped positions between the two photos.
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PXL_20201214_020952144_copy_1612x1209.jpg (647.73 KiB) Viewed 338 times

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Re: Bright and shiny - refractive index question...

Post by monkey » Mon Dec 14, 2020 7:00 pm

dyqik wrote:
Mon Dec 14, 2020 1:18 am
Gfamily wrote:
Sun Dec 13, 2020 11:11 pm
A transition from whisky to gin over the last few years makes me ask whether it's an illusion that a glass of gin seems to be much brighter than a glass containing the same amount of water?
Is it optics or anticipation?
It's quite possible for a few reasons:

1) the refractive index of 40% alcohol in solution is a bit higher than that of plain water, and closer to that of glass, which means less reflection loss at the interfaces from glass to booze, as well as different critical angles and refraction (which is how alcohol content can be measured with a refractometer), which may bring more light through.

2) gin may be slightly bluer than water, making it look a little brighter.

3) quinine is fluorescent, so a g&t (and maybe some gins as well) will fluoresce if there's UV around.
Related to refractive index, there's also dispersion to consider. I think refractive/reflective stuff changing what the reflections is doing is the most likely explanation for the effect, (if there is one).

On 2) I think absorption or scattering effects would be gin specific, not sure ethanol and water are all that different in the visible range on that score.

I doubt it's 3), with normal lightning the fluorescence would be too weak I reckon. As a note, Fluorescence is also dependent on what else in the solution - you can quench the fluorescence in toinc water with table salt. I use this in a demonstration to show that you have to be careful with or know what your target molecule is in when doing fluorescence microscopy.

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Re: Bright and shiny - refractive index question...

Post by monkey » Mon Dec 14, 2020 8:06 pm

Oh I forgot to add, photos might not be the best way to compare. Your visual system might respond to a real life object differently to an RGB representaion. E.g. it might be be noticing different glimmery stuff happening cos of movement of the liquid and your eye, or an RGB image might not give you the same responses as with a continuous spectrum.

It might not just be optic effects, but neuroscience too.

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Re: Bright and shiny - refractive index question...

Post by dyqik » Mon Dec 14, 2020 8:14 pm

monkey wrote:
Mon Dec 14, 2020 8:06 pm
Oh I forgot to add, photos might not be the best way to compare. Your visual system might respond to a real life object differently to an RGB representaion. E.g. it might be be noticing different glimmery stuff happening cos of movement of the liquid and your eye, or an RGB image might not give you the same responses as with a continuous spectrum.

It might not just be optic effects, but neuroscience too.
Viscosity affecting the movement and shimmer is a good call. Another one I'd suggest is suspended solids or bubbles in each of the two liquids.

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Re: Bright and shiny - refractive index question...

Post by dyqik » Mon Dec 14, 2020 8:17 pm

monkey wrote:
Mon Dec 14, 2020 7:00 pm

I doubt it's 3), with normal lightning the fluorescence would be too weak I reckon. As a note, Fluorescence is also dependent on what else in the solution - you can quench the fluorescence in toinc water with table salt. I use this in a demonstration to show that you have to be careful with or know what your target molecule is in when doing fluorescence microscopy.
Yeah, it's unlikely to show up under sunlight, incandescent or most regular lighting. It might show up in a darker room with full-spectrum grow lights or something.

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Re: Bright and shiny - refractive index question...

Post by monkey » Mon Dec 14, 2020 8:50 pm

dyqik wrote:
Mon Dec 14, 2020 8:14 pm
monkey wrote:
Mon Dec 14, 2020 8:06 pm
Oh I forgot to add, photos might not be the best way to compare. Your visual system might respond to a real life object differently to an RGB representaion. E.g. it might be be noticing different glimmery stuff happening cos of movement of the liquid and your eye, or an RGB image might not give you the same responses as with a continuous spectrum.

It might not just be optic effects, but neuroscience too.
Viscosity affecting the movement and shimmer is a good call. Another one I'd suggest is suspended solids or bubbles in each of the two liquids.
I was thinking more about the visual system responds to stimulii rather than how the gin behaves, but yeah, viscosity and bubbles might be changing the glimmer.

I don't think you can ignore the visual system, how it responds to the optical differences might be giving a perception that the differences are greater than they are.

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Re: Bright and shiny - refractive index question...

Post by dyqik » Mon Dec 14, 2020 9:23 pm

monkey wrote:
Mon Dec 14, 2020 8:50 pm
dyqik wrote:
Mon Dec 14, 2020 8:14 pm
monkey wrote:
Mon Dec 14, 2020 8:06 pm
Oh I forgot to add, photos might not be the best way to compare. Your visual system might respond to a real life object differently to an RGB representaion. E.g. it might be be noticing different glimmery stuff happening cos of movement of the liquid and your eye, or an RGB image might not give you the same responses as with a continuous spectrum.

It might not just be optic effects, but neuroscience too.
Viscosity affecting the movement and shimmer is a good call. Another one I'd suggest is suspended solids or bubbles in each of the two liquids.
I was thinking more about the visual system responds to stimulii rather than how the gin behaves, but yeah, viscosity and bubbles might be changing the glimmer.

I don't think you can ignore the visual system, how it responds to the optical differences might be giving a perception that the differences are greater than they are.
No, but cameras are much more sensitive and stable than eyes. You could do some analysis on images to look for consistent differences, for example.

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Re: Bright and shiny - refractive index question...

Post by Boustrophedon » Mon Dec 14, 2020 10:02 pm

dyqik wrote:
Mon Dec 14, 2020 1:18 am
Gfamily wrote:
Sun Dec 13, 2020 11:11 pm
A transition from whisky to gin over the last few years makes me ask whether it's an illusion that a glass of gin seems to be much brighter than a glass containing the same amount of water?
Is it optics or anticipation?
It's quite possible for a few reasons:

1) the refractive index of 40% alcohol in solution is a bit higher than that of plain water, and closer to that of glass, which means less reflection loss at the interfaces from glass to booze, as well as different critical angles and refraction (which is how alcohol content can be measured with a refractometer), which may bring more light through.

2) gin may be slightly bluer than water, making it look a little brighter.

3) quinine is fluorescent, so a g&t (and maybe some gins as well) will fluoresce if there's UV around.
When I was a student there was a nightclub that lit the area behind one of the bars with a bright UV source and a shelves of tonic water.
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Re: Bright and shiny - refractive index question...

Post by monkey » Tue Dec 15, 2020 12:00 am

dyqik wrote:
Mon Dec 14, 2020 9:23 pm
monkey wrote:
Mon Dec 14, 2020 8:50 pm
dyqik wrote:
Mon Dec 14, 2020 8:14 pm


Viscosity affecting the movement and shimmer is a good call. Another one I'd suggest is suspended solids or bubbles in each of the two liquids.
I was thinking more about the visual system responds to stimulii rather than how the gin behaves, but yeah, viscosity and bubbles might be changing the glimmer.

I don't think you can ignore the visual system, how it responds to the optical differences might be giving a perception that the differences are greater than they are.
No, but cameras are much more sensitive and stable than eyes. You could do some analysis on images to look for consistent differences, for example.
I agree, a camera would be better for measuring the optical differences, or finding out if there are any. But you can't ignore the visual system, it's obviously involved in how Gfamily perceives the gin. I've been invovled with visual psychophysics before*. One of the things you've got to be really careful about is that the subject is blind to the condition being tested, because that can change the result. So I'm thinking that there are some optical changes, but the perception of those changes might be influenced by the visual system being good at spotting those, with some possible additional effect due to subjective expectation. (Or Gfamily is just making the whole thing up)


Here's another one: My boss just suggested differences in the meniscus, and Gfamily might be picking up on differences where the gin/water surface meets the glass. He also says that Bourbon is fluorescent too, not sure if he meant all Bourbons or just some though. (His first response was "you'd have to blind test that")


*I do optics for a vision scientist. I'm bad at vision science and good at optics, but he's bad at optics and is good at vision science. I do not claim to be a vision scientist.

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Re: Bright and shiny - refractive index question...

Post by Gfamily » Tue Dec 15, 2020 12:07 am

When I have company I'll get someone to prepare a glass with gin and a glass with water and see if I can tell them apart.

Cheers all
Chin chin!
My avatar was a scientific result that was later found to be 'mistaken' - I rarely claim to be 100% correct
ETA 5/8/20: I've been advised that the result was correct, it was the initial interpretation that needed to be withdrawn
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Re: Bright and shiny - refractive index question...

Post by dyqik » Tue Dec 15, 2020 12:44 am

monkey wrote:
Tue Dec 15, 2020 12:00 am
dyqik wrote:
Mon Dec 14, 2020 9:23 pm
monkey wrote:
Mon Dec 14, 2020 8:50 pm


I was thinking more about the visual system responds to stimulii rather than how the gin behaves, but yeah, viscosity and bubbles might be changing the glimmer.

I don't think you can ignore the visual system, how it responds to the optical differences might be giving a perception that the differences are greater than they are.
No, but cameras are much more sensitive and stable than eyes. You could do some analysis on images to look for consistent differences, for example.
I agree, a camera would be better for measuring the optical differences, or finding out if there are any. But you can't ignore the visual system, it's obviously involved in how Gfamily perceives the gin. I've been invovled with visual psychophysics before*. One of the things you've got to be really careful about is that the subject is blind to the condition being tested, because that can change the result. So I'm thinking that there are some optical changes, but the perception of those changes might be influenced by the visual system being good at spotting those, with some possible additional effect due to subjective expectation. (Or Gfamily is just making the whole thing up)


Here's another one: My boss just suggested differences in the meniscus, and Gfamily might be picking up on differences where the gin/water surface meets the glass. He also says that Bourbon is fluorescent too, not sure if he meant all Bourbons or just some though. (His first response was "you'd have to blind test that")


*I do optics for a vision scientist. I'm bad at vision science and good at optics, but he's bad at optics and is good at vision science. I do not claim to be a vision scientist.
Any thing the visual system picks up is the result of easily measurable physical optics.

It might not be obvious how the physical difference is related to what the brain picks up, but it'll be easily measurable.

Differences in the wetting of the glass are another good option for a physical difference.

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Re: Bright and shiny - refractive index question...

Post by dyqik » Tue Dec 15, 2020 1:25 am

Amaretto, birch liqueur, Elijah Craig bourbon, Element Distilling whisky, Glenlivet 12 YO and Nashoba New Wave Gin are all fluorescent. Liqueur 43, tequila, rum and pisco aren't.

The first two particularly so.

It's the oaking that stands out as common in most of those, except the gin.

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Re: Bright and shiny - refractive index question...

Post by monkey » Tue Dec 15, 2020 1:57 am

dyqik wrote:
Tue Dec 15, 2020 12:44 am
Any thing the visual system picks up is the result of easily measurable physical optics.

It might not be obvious how the physical difference is related to what the brain picks up, but it'll be easily measurable.

Differences in the wetting of the glass are another good option for a physical difference.
If you're referring to the response/perception here: no, it's not that easy. But that's why I have a job :)

I was just thinking about wine legs, after pouring a glass.

Gfamily wrote:
Tue Dec 15, 2020 12:07 am
When I have company I'll get someone to prepare a glass with gin and a glass with water and see if I can tell them apart.

Cheers all
Chin chin!
Make sure to get in a few repeats.

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Re: Bright and shiny - refractive index question...

Post by dyqik » Tue Dec 15, 2020 3:05 am

monkey wrote:
Tue Dec 15, 2020 1:57 am
dyqik wrote:
Tue Dec 15, 2020 12:44 am
Any thing the visual system picks up is the result of easily measurable physical optics.

It might not be obvious how the physical difference is related to what the brain picks up, but it'll be easily measurable.

Differences in the wetting of the glass are another good option for a physical difference.
If you're referring to the response/perception here: no, it's not that easy. But that's why I have a job :).
No, I'm referring to the physical differences that the eyes are feeding to the brain to pick-up on.

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Re: Bright and shiny - refractive index question...

Post by Martin_B » Tue Dec 15, 2020 3:17 am

dyqik wrote:
Tue Dec 15, 2020 1:25 am
Amaretto, birch liqueur, Elijah Craig bourbon, Element Distilling whisky, Glenlivet 12 YO and Nashoba New Wave Gin are all fluorescent. Liqueur 43, tequila, rum and pisco aren't.

The first two particularly so.

It's the oaking that stands out as common in most of those, except the gin.
I think we now know the contents of dyqik's liquor cabinet!
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Re: Bright and shiny - refractive index question...

Post by monkey » Tue Dec 15, 2020 3:38 am

dyqik wrote:
Tue Dec 15, 2020 3:05 am
monkey wrote:
Tue Dec 15, 2020 1:57 am
dyqik wrote:
Tue Dec 15, 2020 12:44 am
Any thing the visual system picks up is the result of easily measurable physical optics.

It might not be obvious how the physical difference is related to what the brain picks up, but it'll be easily measurable.

Differences in the wetting of the glass are another good option for a physical difference.
If you're referring to the response/perception here: no, it's not that easy. But that's why I have a job :).
No, I'm referring to the physical differences that the eyes are feeding to the brain to pick-up on.
Yeah, that bits easy. We could even do some measurements on Gfamily and simulate what the image on his retina looks like.

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Re: Bright and shiny - refractive index question...

Post by dyqik » Tue Dec 15, 2020 6:08 pm

:D
Martin_B wrote:
Tue Dec 15, 2020 3:17 am
dyqik wrote:
Tue Dec 15, 2020 1:25 am
Amaretto, birch liqueur, Elijah Craig bourbon, Element Distilling whisky, Glenlivet 12 YO and Nashoba New Wave Gin are all fluorescent. Liqueur 43, tequila, rum and pisco aren't.

The first two particularly so.

It's the oaking that stands out as common in most of those, except the gin.
I think we now know the contents of dyqik's liquor cabinet!
You know what's in the clear bottles at the front of the shelves...

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Re: Bright and shiny - refractive index question...

Post by monkey » Tue Dec 15, 2020 6:19 pm

dyqik wrote:
Tue Dec 15, 2020 6:08 pm
:D
Martin_B wrote:
Tue Dec 15, 2020 3:17 am
dyqik wrote:
Tue Dec 15, 2020 1:25 am
Amaretto, birch liqueur, Elijah Craig bourbon, Element Distilling whisky, Glenlivet 12 YO and Nashoba New Wave Gin are all fluorescent. Liqueur 43, tequila, rum and pisco aren't.

The first two particularly so.

It's the oaking that stands out as common in most of those, except the gin.
I think we now know the contents of dyqik's liquor cabinet!
You know what's in the clear bottles at the front of the shelves...
Actually, what wavelength were you using? We use a 405 nm (IRC) laser pointer for our demonstrations.

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Re: Bright and shiny - refractive index question...

Post by dyqik » Tue Dec 15, 2020 8:43 pm

monkey wrote:
Tue Dec 15, 2020 6:19 pm
dyqik wrote:
Tue Dec 15, 2020 6:08 pm
:D
Martin_B wrote:
Tue Dec 15, 2020 3:17 am


I think we now know the contents of dyqik's liquor cabinet!
You know what's in the clear bottles at the front of the shelves...
Actually, what wavelength were you using? We use a 405 nm (IRC) laser pointer for our demonstrations.
Whatever came in the UV LED flashlight I bought on Amazon for $7 to look for oil leaks (with a dye in the oil) on my Subaru.

ETA: 395nm according to the Amazon page.

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Re: Bright and shiny - refractive index question...

Post by Bird on a Fire » Wed Dec 16, 2020 7:03 pm

dyqik wrote:
Tue Dec 15, 2020 1:25 am
Amaretto, birch liqueur, Elijah Craig bourbon, Element Distilling whisky, Glenlivet 12 YO and Nashoba New Wave Gin are all fluorescent. Liqueur 43, tequila, rum and pisco aren't.

The first two particularly so.

It's the oaking that stands out as common in most of those, except the gin.
Re: oaking, I note that the peak fluorescence of tannin extract is about 400 nm, according to these lecture slides https://www.researchgate.net/profile/An ... ugenia.pdf So that's pretty close to the wavelength you were using.

Doesn't explain the gin though.
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Re: Bright and shiny - refractive index question...

Post by dyqik » Wed Dec 16, 2020 9:00 pm

Bird on a Fire wrote:
Wed Dec 16, 2020 7:03 pm
dyqik wrote:
Tue Dec 15, 2020 1:25 am
Amaretto, birch liqueur, Elijah Craig bourbon, Element Distilling whisky, Glenlivet 12 YO and Nashoba New Wave Gin are all fluorescent. Liqueur 43, tequila, rum and pisco aren't.

The first two particularly so.

It's the oaking that stands out as common in most of those, except the gin.
Re: oaking, I note that the peak fluorescence of tannin extract is about 400 nm, according to these lecture slides https://www.researchgate.net/profile/An ... ugenia.pdf So that's pretty close to the wavelength you were using.

Doesn't explain the gin though.
The gin may have some light oaking or tannin. It's a not very good and pretty harsh gin from a nearby winery.

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Re: Bright and shiny - refractive index question...

Post by monkey » Wed Dec 16, 2020 11:35 pm

Bird on a Fire wrote:
Wed Dec 16, 2020 7:03 pm
dyqik wrote:
Tue Dec 15, 2020 1:25 am
Amaretto, birch liqueur, Elijah Craig bourbon, Element Distilling whisky, Glenlivet 12 YO and Nashoba New Wave Gin are all fluorescent. Liqueur 43, tequila, rum and pisco aren't.

The first two particularly so.

It's the oaking that stands out as common in most of those, except the gin.
Re: oaking, I note that the peak fluorescence of tannin extract is about 400 nm, according to these lecture slides https://www.researchgate.net/profile/An ... ugenia.pdf So that's pretty close to the wavelength you were using.

Doesn't explain the gin though.
If I'm looking at the right graph, the tannin extract needs an excitation wavelength much shorter than what dyqik was using, so it might not be the them, but I'm betting there's more than tannins that get into the spirit when it's left in a barrel. And solutions can make things complicated.

This paper on Tequila suggests that it is something to do with the aging process. They test various tequilas at various excitation wavelengths. Only the aged and mixed (having some aged component) ones fluoresce at 405 nm, close to the LED used. Dyqik's tequila might be fake.

You get all sorts of stuff put in Gin. Could be anything causing the fluorescence for that.

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Re: Bright and shiny - refractive index question...

Post by Bird on a Fire » Thu Dec 17, 2020 12:20 am

Ah, thanks for the correction.

I'm intrigued. I want to know what's making dyqik's spirits fluoresce.
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