Fluorescence (revisited)

[Rockdiamond]

Bryan- if progress means I don't see what I have seen for over 40 years, we're not going to make any progress at all.

When I was training at Harry Winston, in the late 1970's- the "fluorescence situation" was totally opposite of today.
At that time, certain fluorescent stones of high color were categorized as "Premier" and sold at a premium over non fluorescent stones- or fluorescent diamonds that did not have this unique characteristic.
The charachteristic is that the stone looks kind of blue in many normal viewing envonments.
Of course the powers that be'd at the time at Winston had never read the report you're clinging to- so they didn't know they weren't seeing what they were seeing.

It's really not a black and white issue- as there's different types of fluorescence.
Not every MB or SB stone will exhibit the same type of color change as others.

This is a physical reality, as opposed to the paper you're standing by- which is by no means widely accepted.
We both agree that MB or SB stones can be attractive- and can be sound values- I just like them better than you- or I see advantages you don't.
I have found many people that also see these advantages- but if you can't, we will have to agree to disagree.
I have no doubt my eyes see what they see.

 

[Garry H (Cut Nut)]

Hi Garry,
Appreciate your participation here. Interesting points about the different devices/procedures used to grade fancy colors. I was not aware of that. It does point up the variables introduced by different light sources, devices and procedures being imployed by the labs and in the trade in assessing fluorescence. And the changes that take place that might affect consistency of grading over time.

I was also not aware that GIA has changed their color grading lamps or procedures since the Cowing study. Can you elaborate on that? Was it a response to the study?

I believe the diamond story that Michael showcased in his article that dropped 4 grades when UV light was screened out of a grading lamp was graded a long time ago. GIA never formally 'announced' they changed their grading lamps - but Marty Haske drove them nuts and I suspect it was about 15 years ago. Michaels influence would have been way less than Marty's - you can search on this forum some references from Martin. His website has disappeared - I think he is unwell. Anyone know?

I'm unclear about what point you are making. In the absence of a change in the lighting and/or procedures since 2010 then the same issue continues as illustrated and explained in detail in the Cowing study. Are you disputing any aspects of that study or the science behind it?

It is actually the science behind the study which is most relevant to the question of real world benefit to appearance of fluorescent diamonds. I have found not a single person who points to any inaccuracies in the measurements referenced or the conclusions regarding under what circumstances fluorescence is activated.

The color grading piece is actually a separate and obviously related one that has far reaching implications for the market. But I think it is just as important for consumers to understand clearly whether or not the supposed "benefits" of fluorescence are scientifically supportable.

Brian I am not happy to grade diamonds in pure LED lighting until that lighting becomes the norm in peoples living and working environments.
I think Michael is a serious and dedicated gemologist who has my respect, but I would like to see an organisation or someone reproduce the results before I would be convinced that there is no unintended bias.

 

[Garry H (Cut Nut)]

From page 82 in G&G summer 2013
file:///C:/Users/Garry/Downloads/SU13.pdf
This is a heavy article but shows that the frequency of emission of your UV light source is a very complex issue.
My layman-gemo opinion is that UV light closer to the visible end of vilolet light may be more important than the "long" wavelength used by gemologists (that was primarily employed as a part of the system of identifying different colored gemstones).
This near visible UV light is possibly far more common in our every day environments.
I hope that adds to the discussion and shows why I think its hard to make definitive conclusions.

 

[Texas Leaguer]

From page 82 in G&G summer 2013
file:///C:/Users/Garry/Downloads/SU13.pdf
This is a heavy article but shows that the frequency of emission of your UV light source is a very complex issue.
My layman-gemo opinion is that UV light closer to the visible end of vilolet light may be more important than the "long" wavelength used by gemologists (that was primarily employed as a part of the system of identifying different colored gemstones).
This near visible UV light is possibly far more common in our every day environments.
I hope that adds to the discussion and shows why I think its hard to make definitive conclusions.

Garry,
Can you repost the link to the article. I would like to look at it.

No doubt that the effects are complex.

The Cowing article does discuss in some detail the discovery that certain wavelenths in the visible spectrum can excite flourescence. But again, unless an intensity level is achieved by viewing in sunlight or by positioning the stone extremely close to an artificial source containing these wavelengths, the energy is not sufficient to activate the fluorescence or it's masking effect.

My intent was not to focus on the over-grading aspect in this discussion (though it is important). I was citing the Cowing study for the science behind it and the implications it has for the consumer in terms of what visual benefits can be expected when considering the purchase of a fluoro stone. Any benefits must be properly weighed against factors such as transparency and future liquidity. Assessing price advantage must also take into account the level of certainty regarding the color grade.

 

[Rockdiamond]

Bryan- while I truly love the discourse and exchange of ideas, I regret that this discussion seems to have us at odds.
Surely we can have different opinions yet agree that we're both looking out for consumer education.

Back to the subject at hand...
If we use a stone that's SB (one of the small percentage that is milky), as an example: In my experience such stones remain milky regardless of what type of light you view them in.
This is a positive for consumers- as one needs no training or special equipment to spot a problematic fluorescent diamond.
And it also points to the fact that certain fluorescent diamonds react to whatever amount of UV is contained in normal lighting.

 

[Texas Leaguer]

Bryan- while I truly love the discourse and exchange of ideas, I regret that this discussion seems to have us at odds.
Surely we can have different opinions yet agree that we're both looking out for consumer education.

Back to the subject at hand...
If we use a stone that's SB (one of the small percentage that is milky), as an example: In my experience such stones remain milky regardless of what type of light you view them in.
This is a positive for consumers- as one needs no training or special equipment to spot a problematic fluorescent diamond.
And it also points to the fact that certain fluorescent diamonds react to whatever amount of UV is contained in normal lighting.

If it is milky regardless of what type of light you view it in, the milkiness has nothing to do with fluorescence.

 

[Rockdiamond]

Bryan, in your experience, do hazy fluorescent stones look brilliant and shiny indoors, away from a window?


Of course Garry's point is a good one- to actually see a diamond sparkle, you need a certain amount of light.
But the hazy SB stones I've seen remained hazy ( also could be described as "oily" appearance) if you had even a small bit of light.

 

[Texas Leaguer]

Bryan, in your experience, do hazy fluorescent stones look brilliant and shiny indoors, away from a window?


Of course Garry's point is a good one- to actually see a diamond sparkle, you need a certain amount of light.
But the hazy SB stones I've seen remained hazy ( also could be described as "oily" appearance) if you had even a small bit of light.

If a fluoro stone is clean enough and cut well enough it will have good light performance when not exposed to strong UV. You see examples all the time posted on pricescope. You see some milkiness in the outdoor shots and normal transparency in indoor shots.

Fluorescent stones often have clarity characteristics that can compromise transparency such as twinning and graining. These do not go away when you remove the stone from direct sunlight. So there can be two things going on that can both impact the visual appearance in a negative way, and they are independent of one another.

 

[Rockdiamond]

Bryan, the type of problematic fluorescence I'm referring to has nothing to do with clarity characteristics. I'm talking about oily looking stones- it's a small percentage of fluorescent diamonds, but in this small group, the entire body of the diamond is dull. Cut and lack of imperfections will have no positive bearing on this aspect.
It's incredibly easy to spot, maybe you've not seen one......

 

[Texas Leaguer]

Bryan, the type of problematic fluorescence I'm referring to has nothing to do with clarity characteristics. I'm talking about oily looking stones- it's a small percentage of fluorescent diamonds, but in this small group, the entire body of the diamond is dull. Cut and lack of imperfections will have no positive bearing on this aspect.
It's incredibly easy to spot, maybe you've not seen one......

No David, you fail to understand what I am saying. I am sorry, I am really trying to be precise with my words.

I have see many milky fluorescent stones in my time, just as you describe. The point is that if the transparency problem is arising as a result of the fluorescence, when you take the stone away from light that is incapable of activating the fluorescent effect, the transparency problem disappears.

The big negative associated with fluoro stones, that of milkiness/oiliness, is an over blown concern for exactly the same reason the supposed benefits of color masking are overstated.

 

[Rockdiamond]

I don't know Bryan, maybe the light is different in Texas. The bad fl stones I've seen were bad in any light which was sufficient to see them in detail.

 

[Texas Leaguer]

I don't know Bryan, maybe the light is different in Texas. The bad fl stones I've seen were bad in any light which was sufficient to see them in detail.

That must be it David. Like everything else, the light is BIGGER in Texas.

 

[Garry H (Cut Nut)]

Guys glad to see you both playing a tiny little bit better in the sand pit.

I agree Bryan that if you screen out light with Lexan (as you can see half way through this 2 minute video) http://www.hollowaydiamonds.com.au/fluorescence then any haziness caused by fluoro will disappear. But may i please reiterate that the apparent color improvement does appear to be real to me in many real life environments where there is adequate light. If you are in a dim restaurant none of us can tell the difference between a I and a D, but if you compare a +1ct G Strong blue fluorescent stone to a D in a well artificaially lit office then I find its near impossible to tell the difference.

That earlier url may need to be copied and pasted - its a G&G pdf download Bryan, or just search for summer 2013.
file:///C:/Users/Garry/Downloads/SU13.pdf

 

[Rockdiamond]

I need to find a really bad example of an oily stone- the video was very good (One thing I'll say- you're a good looking son of a gun Garry- but the part with the oily stone didn't depict the look I'm referring to - the look I'm referring to is way worse than the stone in the video.

Playing nice is way more fun

 

[Garry H (Cut Nut)]

I need to find a really bad example of an oily stone- the video was very good (One thing I'll say- you're a good looking son of a gun Garry- but the part with the oily stone didn't depict the look I'm referring to - the look I'm referring to is way worse than the stone in the video.

Playing nice is way more fun

The stone in the video is one I would reject (for most people) beacuse it is over blue. It may not have shown haziness or oilyness in real life but would be blueish in daylight.
I got the stone in to make the video - i would not stock that - but have occasionally been asked to find one to match another like it.