When do we get fire? Why is it sometimes pastel?

[kenny]

Here is my understanding and some thoughts.
Discussion and corrections are welcome.

White light is actually a mixture of all colors.
Fire is the dispersion of white light into its component colors.
It happens when the all the angles are just right ... not just the angles of the effective-prisms in the diamond (it happens more with good cut than poor cut) but also the angle the light source makes.
The angle depends on the light source's size and its distance to the diamond.

Generally we think fire depends on the size of the light source.
Small source = fire ... like a tiny halogen bulb at the ceiling.
Large source = no fire ... a very cloudy sky which presents a 180 degree flat even dome of light.

But fire is not actually dependent of the size of the light source, it depends on the angle the light presents AT the diamond.
For instance with a diameter of 1.4 million Kilometers the sun is a rather large light source, so it should not produce fire.
But it does.
Why?
Because it's so far away.

Similarly the same 6" can light fixture in the ceiling that produces lots fire will produce no fire if you move it close enough to the diamond.

To illustrate this see drawing below.
Notice how the angle of the light the diamond 'sees' increases as the distance decreases, even though the size of the light source remains the same.

 

[kenny]

Why do we sometimes see pastels?

I suspect we get pastels when there are multiple light sources with different sizes (again effective-angles) which is very common in real life.

The smallest light source is responsible for the dispersion and color we see, but the larger light source is responsible for 'polluting' this color by mixing in some returned white light from the larger light source.

Like paint, if you start with a strong rich color but then mix in enough white you get a pastel, same hue just lower color saturation.

To illustrate this imagine an experimental room with walls, floor and ceiling painted flat black.
The only light source is one tiny bright halogen bulb at the ceiling.
You are wearing a black burka so you reflect no light.
A diamond here will produce fire of the most intense saturated color.

Next, with the halogen light still on image you could somehow change the black room to gradually become lighter, as if all six sides had zillions of even light sources behind translucent white paper walls that you could gradually turn up.
As the environment brightened the fire from the diamond would gradually change from strong saturated colors to pastels.

I can't visualize how pastels could be the result of larger facets, a connection I read about especially with GOG's lovely August Vintage Cushions.
We do see pastels in the videos GOG shoots near their store's front windows.

I think this environment just happens to have a combination of light sources that is particularly conducive to pastels, some small and some large light sources.
THAT the color is pastel is just more noticeable in a larger facet than in a smaller facet.
Very bright fire, such as under sunlight, blows your head off so much the size of the facet matters less ... this may help explain the incorrrect association of pastels with larger facets.

I see pastel dispersion in a store that has rows of wall to wall fluorescent fixtures mounted on a very white ceiling, an ideal example.
We don't think of a ceiling or walls as light sources, but everything around you that isn't flat black can and will reflect light and your diamond 'sees' all.

 

[ForteKitty]

Sorry Kenny, all I saw were snowcones.

 

[kenny]

Hahahaha.

 

[Rhino]

I think there are a number of things that come into play Ken but the size of the facets coupled with ideal optics are, IMPO the two key contributing factors. If you look at videos I've done with modern faceted diamonds that feature smaller reflections you can also see pastels although they are really very small reflections that get lost in the abundance of white light.

Not sure if it's so much the distance of the lighting as it is the intensity of the lighting that produce fire.

All the best,
Rhino

 

[kenny]

Rhino, did you say something?
I saw this, which told me you posted something around 40 minutes ago.



... so I clicked on the icon next to 'Rhino'.
But instead of seeing your post, I saw this.



So, then I clicked on the thread itself and scrolled down to the bottom to see your post but it wasn't there ... my last post was at the bottom of the thread ...



What gives?

Rhino, you have my email address ...
Hope I didn't inadvertently offend you.
Hope you can contribute to this thread about what causes us to see pastels.
I really think it is unrelated to cut.
Rather, it is a function of lighting in the environment.

 

[kenny]

Wow!
How bizarre!
Rhino, your post has magically appeared before my most-recent post AFTER I posted it.
Did you get reported, then modify your post to appease admin?
Either that or I dropped some LSD.

Yes, sure in pastel-conducive lighting pastels will appear in diamonds with large or small facets.
It being pastel will be more noticeable with large facets than small facets, especially for us with old eyes that cannot resolve small detail.

Fire from a 1 ct under direct sunlight that blows your head off will look similar to the fire from a 2 ct of identical cut in identical sunlight.
A blown-off head is a blown-off head.
Being killed by a small bullet to the head is just as dead as being killed with a high-calibre bullet.

Pastels don't blow your head off, so you'll notice pastels more in diamonds with larger facets.

 

[kenny]

Rhino, do you agree pastels are the result of lighting, not cut?

 

[Karl_K]

Kenny,
It is far more complex than that....
The size of the light source the diamond sees does depend on distance.
A standard duel florescent tube light overhead in a 8 foot ceiling overhead is a large light source if it has a defusing panel on it and produces brightness from the diamond, the same light in a 30 foot ceiling in a warehouse store is a small light source and produces fire. Without a defusing panel a single bare florescent tube is a large light source one way and a small one the other which can produce an interesting mix of white light and fire in a diamond even in an 8 foot ceiling.
The sun is small very bright light source relative to the diamond because it is a very small part of the hemisphere over the diamond where the diamond is drawing light.

Where on a diamond a smaller light source strikes the diamond and the angle and where it exits the diamond can have a large effect on how it is returned to the eye either brightness or fire.

Fire in diamonds is extremely complex and not fully understood.
I don't believe it will be ever fully understood because there are simply too many variables.
Take what I just said above, while in very general manner it is that way I can think of several dozen variable that it does not cover.

 

[Karl_K]

Rhino, do you agree pastels are the result of lighting, not cut?

I don't agree.
In the exact same lighting different diamonds particularly different designs will produce different fire.

 

[Gypsy]

Rhino, do you agree pastels are the result of lighting, not cut?

I don't agree.
In the exact same lighting different diamonds particularly different designs will produce different fire.

Not an expert, but from my observations I agree with Karl. You can see it really easily at a PS GTG. Same light, lots of different reactions even among stones of the same spread. You put my stone next to a AVC of the same size, the AVC will give off more pastels than mine will. I honestly get almost no pastels at all from my generic asscher, truth to be told.

 

[marymm]

Purely anecdotally (and likely coincidence?) but I noticed going from smaller E-color WF ACA to slightly larger G-color WF ACA, the fire changed from predominantly pastel and blue fire (in the E) to warmer/more yellow-orange/less-blue fire (in the G).

Similarly, the fire also seems warmer in my H-I old mine cushion diamond as compared to my (smaller) G-color OEC diamonds.

 

[cflutist]

Guys, your techie talk is making my head spin.

So here are some pastel colors in my new 2.21 F-SI1 CBI diamond and I don't know what type of lighting Wink used for this photo:



But why do I still see pastel colors in this picture that was taken in natural lighting in my dining room (no light fixtures of any sort that were on)?



Finally, more pastel colors. This time taken indoors with my phone under a skylight in an overcast/rainy day.
So what's happening to cause this?

 

[Gypsy]

My head is spinning too.

Oh. And FYI. My BGD signatures at .30 points threw fire EVERWHERE and in the same light my asscher was still just sparkling but not firing.

Even my 5 point BGD Signature melee throws more fire than my asscher. It takes JUST THE RIGHT CONDITIONS for my asscher to get fiery and it has a high crown.

 

[Karl_K]

My head is spinning too.

Oh. And FYI. My BGD signatures at .30 points threw fire EVERWHERE and in the same light my asscher was still just sparkling but not firing.

Even my 5 point BGD Signature melee throws more fire than my asscher. It takes JUST THE RIGHT CONDITIONS for my asscher to get fiery and it has a high crown.

different virtual facet sizes respond differently to different lighting and is affected by angle relationships.
The lighting is conductive to fire by tiny virtual facets in the melee but brightness in the larger virtual facets of the asscher.
Larger virtual facets are drawing light from a larger area.
Also try large movements and the asscher should "wake" up it take larger movement to flash larger virtual facets.
That can be modified somewhat by angle relationships and a high crown usually helps in asschers.

 

[Gypsy]

SO I should make it DANCE for the fire?

 

[cflutist]

Kenny,
It is far more complex than that....
The size of the light source the diamond sees does depend on distance.
A standard duel florescent tube light overhead in a 8 foot ceiling overhead is a large light source if it has a defusing panel on it and produces brightness from the diamond, the same light in a 30 foot ceiling in a warehouse store is a small light source and produces fire. Without a defusing panel a single bare florescent tube is a large light source one way and a small one the other which can produce an interesting mix of white light and fire in a diamond even in an 8 foot ceiling.
The sun is small very bright light source relative to the diamond because it is a very small part of the hemisphere over the diamond where the diamond is drawing light.

Where on a diamond a smaller light source strikes the diamond and the angle and where it exits the diamond can have a large effect on how it is returned to the eye either brightness or fire.

Fire in diamonds is extremely complex and not fully understood.
I don't believe it will be ever fully understood because there are simply too many variables.
Take what I just said above, while in very general manner it is that way I can think of several dozen variable that it does not cover.

So that is why our diamonds look so good at Costco and Home Depot. I was at HD yesterday and noticed that the light fixtures above were just plain old fluorescent tubes but that the ceiling was very high.

 

[cflutist]

My head is spinning too.

Oh. And FYI. My BGD signatures at .30 points threw fire EVERWHERE and in the same light my asscher was still just sparkling but not firing.

Even my 5 point BGD Signature melee throws more fire than my asscher. It takes JUST THE RIGHT CONDITIONS for my asscher to get fiery and it has a high crown.

different virtual facet sizes respond differently to different lighting and is affected by angle relationships.
The lighting is conductive to fire by tiny virtual facets in the melee but brightness in the larger virtual facets of the asscher.
Larger virtual facets are drawing light from a larger area.
Also try large movements and the asscher should "wake" up it take larger movement to flash larger virtual facets.
That can be modified somewhat by angle relationships and a high crown usually helps in asschers.

So when we buy a diamond, how do we know what the virtual facet sizes are? Have never seen that listed on a lab report.

 

[Karl_K]

But why do I still see pastel colors in this picture that was taken in natural lighting in my dining room (no light fixtures of any sort that were on)?



Finally, more pastel colors. This time taken indoors with my phone under a skylight and an overcast/rainy day.
So what's happening to cause this?

Lack of reds in the light hitting the diamond makes blue more prominent.
The spectrum of the light hitting the diamond is a huge variable.
Overcast day the reds and yellows are blocked more by the clouds.
Which is why things look grey under clouds.
When it gets to the point everything gets a sicky green cast you know your in for a real storm.
Almost anything can effect the spectrum of light hitting a diamond.
The source, any reflective areas color, any shadows, what color cloths your wearing and your hair color and skin tone all effect the spectrum some parts of the diamond see which in turn changes the color of the fire.
The change to cfl lighting will effect the colors of fire most people see a lot indoors as they replace incandescent lighting.
Even the so called full spectrum cfl bulbs are weak in reds and rich in blues.

 

[Karl_K]

So when we buy a diamond, how do we know what the virtual facet sizes are? Have never seen that listed on a lab report.

very complex subject.
Start is here, while about step cuts it applies to any cut: https://www.pricescope.com/journal/virtual-facets-and-patterns-discussion-about-step-cuts

 

[Karl_K]

Kenny,
It is far more complex than that....
The size of the light source the diamond sees does depend on distance.
A standard duel florescent tube light overhead in a 8 foot ceiling overhead is a large light source if it has a defusing panel on it and produces brightness from the diamond, the same light in a 30 foot ceiling in a warehouse store is a small light source and produces fire. Without a defusing panel a single bare florescent tube is a large light source one way and a small one the other which can produce an interesting mix of white light and fire in a diamond even in an 8 foot ceiling.
The sun is small very bright light source relative to the diamond because it is a very small part of the hemisphere over the diamond where the diamond is drawing light.

Where on a diamond a smaller light source strikes the diamond and the angle and where it exits the diamond can have a large effect on how it is returned to the eye either brightness or fire.

Fire in diamonds is extremely complex and not fully understood.
I don't believe it will be ever fully understood because there are simply too many variables.
Take what I just said above, while in very general manner it is that way I can think of several dozen variable that it does not cover.

So that is why our diamonds look so good at Costco and Home Depot. I was at HD yesterday and noticed that the light fixtures above were just plain old fluorescent tubes but that the ceiling was very high.

yep :}
small light sources(% of the hemisphere) with dark area between them are perfect for generating and viewing of fire. Under a tree on a sun lit day a breeze blowing the leaves gently is another.

 

[marymm]

SO I should make it DANCE for the fire?

Gypsy - love this quote! I can just imagine you coaxing your diamond to "dance, dance, dance for the fire, dammit!"

 

[cflutist]

So when we buy a diamond, how do we know what the virtual facet sizes are? Have never seen that listed on a lab report.

very complex subject.
Start is here, while about step cuts it applies to any cut: https://www.pricescope.com/journal/virtual-facets-and-patterns-discussion-about-step-cuts

Thanks Storm, now you are giving me vertigo

 

[Gypsy]

SO I should make it DANCE for the fire?

Gypsy - love this quote! I can just imagine you coaxing your diamond to "dance, dance, dance for the fire, dammit!"

And it is very likely that is the exact language I'd use. DAMNIT you are going to flash fire.

Would it be a flash dance, then, I wonder?

 

[Dancing Fire]

SO I should make it DANCE for the fire?

Are you talking to me?...

 

[cflutist]

SO I should make it DANCE for the fire?

Are you talking to me?...

LOL, Dancing Fire, let's see your moves

 

[Rhino]

Kenny,
It is far more complex than that....
The size of the light source the diamond sees does depend on distance.
A standard duel florescent tube light overhead in a 8 foot ceiling overhead is a large light source if it has a defusing panel on it and produces brightness from the diamond, the same light in a 30 foot ceiling in a warehouse store is a small light source and produces fire. Without a defusing panel a single bare florescent tube is a large light source one way and a small one the other which can produce an interesting mix of white light and fire in a diamond even in an 8 foot ceiling.
The sun is small very bright light source relative to the diamond because it is a very small part of the hemisphere over the diamond where the diamond is drawing light.

Where on a diamond a smaller light source strikes the diamond and the angle and where it exits the diamond can have a large effect on how it is returned to the eye either brightness or fire.

Fire in diamonds is extremely complex and not fully understood.
I don't believe it will be ever fully understood because there are simply too many variables.
Take what I just said above, while in very general manner it is that way I can think of several dozen variable that it does not cover.

Our local 7-11 has this lighting and to behold an ideal cut in it is awesome. Non diffused fluorescent tubing is IMO as beautiful as observing under a shady tree on a sunny day.

 

[Rhino]

Rhino, do you agree pastels are the result of lighting, not cut?

I don't agree.
In the exact same lighting different diamonds particularly different designs will produce different fire.

+1

To expound ... when discussing diamonds with ideal optics it appears that the more surface area there is for the light to expand upon the greater the chance one will be able to clearly observe these pastels. The absence of virtual facets also, IMPO plays a vital role in this as well. Virtual facets will break up light more as it travels through a diamond and bounces on the pavilion mains. The absence of virtual facets will produce a more direct path for the light to fall upon the large mains of the AVC thus producing the effect.

The lighting I believe is somewhere on the threshold between washed out diffuse lighting (like an overcast day) and spot lighting.

 

[Texas Leaguer]

Interesting discussion Kenny. I think you have hit on many of the key aspects, but as Karl explains it is very complex and ever changing. I think that is what makes fire the most magical aspect of diamond light performance.

Here's a basic observation that I don't know if anyone has mentioned yet. In pictures taken in the real world, well cut diamonds are reflecting various things in the environment including contrasty areas as well as colorful areas. Therefore it is easy to mistake some colored reflections in these pictures (and sometimes in real life) for dispersive color (fire).

There are all kinds of things (light source(s), diamond, environment, observer) that can impact the appearance of fire, how likely it is to be observed, how big the colored sparkles are,and how saturated various hues appear. (An unsaturated hue is essentially a pastel). Color mixing is a possibility both in dispersion on top of reflected color, as well as (I believe) mixing of two dispersive colors on a virtual facet.

 

[Rhino]

Guys, your techie talk is making my head spin.

So here are some pastel colors in my new 2.21 F-SI1 CBI diamond and I don't know what type of lighting Wink used for this photo:



But why do I still see pastel colors in this picture that was taken in natural lighting in my dining room (no light fixtures of any sort that were on)?



Finally, more pastel colors. This time taken indoors with my phone under a skylight in an overcast/rainy day.
So what's happening to cause this?

Hi cflutist

In diamonds with ideal optics like yours you'll get pastels. As to "why" I think I'd sum it up in the following list ...

a. ideal optics
b. intensity of the lighting
c. since diamonds with ideal optics are the best at capturing and reflecting back the surrounding environment you are also seeing reflections of colors within that environment
d. tasty snow cones
e. the larger the facets the easier it will be to resolve. Ie. It will be easier to resolve them off the pavilion mains than the other facets as they are generally going to be the widest/longest facets on the pavilion.

Specifically in your first picture cflutist, that burst of yellow fire appears to be the the result of a spot light which Wink included in the diffuse lighting he was taking the image in. Wink will correct me if I'm wrong. Of the various colors of the spectrum (ROYGBIV) yellow and blue will be the most dominate colors observed when it comes to fire. When it comes to pastels though I'm not sure that same rule plays as I've observed pinks, sky blue, dark blue, yellow, green, orange, etc.