Effect of grease on a diamond

[MrYoung]

Can anyone tell me what the effect of grease does to a diamond?

I would assume it will change the refractive index, depending upon what type of grease it is. Does this mean that there is a type of ideal cut stone that I should avoid because of this?

 

[diamondseeker2006]

I think you should avoid wearing the diamond in grease and stick with an ideal cut diamond.

 

[Kaleigh]

Date: 12/15/2007 4:46:56 PM
Author: diamondseeker2006
I think you should avoid wearing the diamond in grease and stick with an ideal cut diamond.

Ditto.

 

[strmrdr]

greese/dirt/grime makes for a dull diamond of any cut.
Garry feels that shallower ideal cuts are less effected and may be right but it hasnt been proven that it is a large consideration.
Keep em clean if you want em sparky!!

 

[gontama]

Date: 12/15/2007 4:55:56 PM
Author: strmrdr
greese/dirt/grime makes for a dull diamond of any cut.
Garry feels that shallower ideal cuts are less effected and may be right but it hasnt been proven that it is a large consideration.
Keep em clean if you want em sparky!!

No one leaves an expensive gem stone dirty.
This particular claim (looks better when dirty) makes no sense.

 

[strmrdr]

Date: 12/15/2007 5:00:54 PM
Author: gontama

Date: 12/15/2007 4:55:56 PM
Author: strmrdr
greese/dirt/grime makes for a dull diamond of any cut.
Garry feels that shallower ideal cuts are less effected and may be right but it hasnt been proven that it is a large consideration.
Keep em clean if you want em sparky!!

No one leaves an expensive gem stone dirty.
This particular claim (looks better when dirty) makes no sense.

99% of the rings on peoples fingers are dirty and a lot are filthy.
Iv seen a lot of pretty gross ones.
But they are also dirty enough that the cut difference isn''t going too help.

 

[gontama]

99% of diamonds are not well cut. Dirt and grease are often there I believe. Those who do not mind lots of dirt/grease on their stones would/should not even consider the very small, if any, claimed benefit of looking better when dirty. Not through magnified photos, but with my eye, I did not see practical difference between 40.7, 40.8, and 41P (the one we got) when they are dirty. They do not look good no matter the c/p combo.

 

[strmrdr]

Date: 12/15/2007 5:38:04 PM
Author: gontama
99% of diamonds are not well cut. Dirt and grease are often there I believe. Those who do not mind lots of dirt/grease on their stones would/should not even consider the very small, if any, claimed benefit of looking better when dirty. Not through magnified photos, but with my eye, I did not see practical difference between 40.7, 40.8, and 41P (the one we got) when they are dirty. They do not look good no matter the c/p combo.

I think we are on the same page just saying it different.
41p with a resonable crown isnt steep/deep and 40.7 isnt shallow.
in the more common PS combo super-ideals there isnt any difference and dirt will make the any of em look yucky.

 

[risingsun]

Are you asking if you should puposely put grease on your diamond...surely you jest....

 

[Ellen]

Date: 12/15/2007 9:04:43 PM
Author: risingsun
Are you asking if you should puposely put grease on your diamond...surely you jest....

You mean, you don''t?

 

[diamondseeker2006]

LOL, Ellen!

 

[Ellen]

 

[Lynn B]

Get the best cut you can find... and keep it clean.

ETA: OK... just noticed that the OP is in the trade. Well, is it just me really showing my ignorance and this is a good question on a valid subject , or is that a rather strange post from someone in the industry?!

*shrugs*

 

[beaujolais]

I believe it is a very valid question and that he is thinking one level up. He wants to know the scientific reasoning for how, exactly, grease interferes.

Also, he is asking if any specific cut may be less prone to grease interference.

 

[Lynn B]

Date: 12/15/2007 9:55:20 PM
Author: sonomacounty
I believe it is a very valid question and that he is thinking one level up. He wants to know the scientific reasoning for how, exactly, grease interferes.

Also, he is asking if any specific cut may be less prone to grease interference.

Well, see then, I knew it. I''m just showing my own stupidity!

(But I still think just keeping it clean is the easiest and best solution!)

 

[diamondseeker2006]

No diamond is going to look great with grease. You shouldn''t wear the ring while working with grease. If you do, then you immediately clean it. There may be a scientific answer, but the common sense answer is really adequate!

 

[Kaleigh]

Grease and diamonds don''t go well together, should be avoided at all costs. Is that scientific enough?

 

[DiamondExpert]

RI (refractive index) and CA (critical angle - the angle outside of which light can strike a plane (internal facet) and remain within the gem) are inversely related, so as you decrease the "effective" RI (dirt/grease) you increase the "effective" CA, thus you decrease the amount of light coming out of crown of the stone because there is a smaller angle with which light can hit a plane (say an internal pavilion facet) and still stay within the stone...i.e., more light leakage.

Just an idea IF dirt/grease, in fact, they do decrease RI.

 

[gontama]

Date: 12/15/2007 8:17:43 PM
Author: strmrdr

Date: 12/15/2007 5:38:04 PM
Author: gontama
99% of diamonds are not well cut. Dirt and grease are often there I believe. Those who do not mind lots of dirt/grease on their stones would/should not even consider the very small, if any, claimed benefit of looking better when dirty. Not through magnified photos, but with my eye, I did not see practical difference between 40.7, 40.8, and 41P (the one we got) when they are dirty. They do not look good no matter the c/p combo.

I think we are on the same page just saying it different.
41p with a resonable crown isnt steep/deep and 40.7 isnt shallow.
in the more common PS combo super-ideals there isnt any difference and dirt will make the any of em look yucky.

Right ... By the way, your new avatar is really cool. I can see it easily gets triple very high...

 

[risingsun]

Date: 12/15/2007 9:20:57 PM
Author: Ellen

Date: 12/15/2007 9:04:43 PM
Author: risingsun
Are you asking if you should puposely put grease on your diamond...surely you jest....

You mean, you don't?

You should be skulking off!! The answer to my question is, "and don't call me Shirley."

I think it's from one of the Airplane movies

And, yes, I do grease my diamonds on a regular basis

 

[Ellen]

Date: 12/16/2007 12:26:32 AM
Author: risingsun
You should be skulking off!! The answer to my question is, ''and don''t call me Shirley.''

I think it''s from one of the Airplane movies

And, yes, I do grease my diamonds on a regular basis

Lynn, I was kind of scratching my head too.

 

[WinkHPD]

Date: 12/15/2007 9:55:20 PM
Author: sonomacounty
I believe it is a very valid question and that he is thinking one level up. He wants to know the scientific reasoning for how, exactly, grease interferes.


Also, he is asking if any specific cut may be less prone to grease interference.

Let''s see if I can remember some of my basic gemology.

As I recall, the refractive index is the difference between the speed of light in air and the speed of light in an optically dense media. When you add an optically dense media such as grease to the outside of as diamond you decrease the apparent refractive index in the diamond because of the difference of the speed of light in grease versus the speed of light in diamond, causing a decrease in the beauty and sparkle in the diamond as more light is allowed out the bottom of the stone, thus returning less light to the eye of the beholder.

This effect can be seen whether the grease is applied to the top, or the bottom of the stone. An easy example is to brush a fingertip on the side of your nose and then across the top of your diamond. You will NOT like the result, unless of course you do not like sparkle...

Wink

P.S. Since a round brilliant cut diamond is the most brilliant of all diamonds, I do not believe that there is a cut that will be more prone to showing less decrease in beauty than a round, and a round shows it plenty!

 

[risingsun]

 

[denverappraiser]

The critical angle has to do with the RI of diamond and the RI of air, both of which are reasonably constant. The quality of the reflection has to do with the critical angle and the polish. Adding grease messes with both of these.

A grease-coated diamond no longer is a diamond/air interface. Internally the light path involves a new interface, diamond/grease and externally it’ll be grease/air. These too will have critical angles but they will be different and it will have to do with the optical qualities of the grease used as well as the properties of diamonds and air. If this was known at the beginning it would be theoretically possible to optimize a cut for this but such a stone would look worse when it was clean or if it was messed up with a different sort of goo.

The polish issue is equally grim. Done well, diamonds take an extremely high quality polish. It’s one of the best materials in the world for this. The grease/air surface is unlikely to be anything like as good as the underlying diamond/air surface was, which means that surface reflections will be worse as well.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

 

[risingsun]

Dear Wink and Neil~forgive me for making light of your erudite explanations. It''s beginning to sound a bit like the calculations involved in determining the air velocity of a European versus an African swallow. I shall go quietly now...

 

[denverappraiser]

Date: 12/16/2007 1:02:40 PM
Author: risingsun
Dear Wink and Neil~forgive me for making light of your erudite explanations. It's beginning to sound a bit like the calculations involved in determining the air velocity of a European versus an African swallow. I shall go quietly now...

Marian,

I'm not sure about grease-laden swallows, but this is the data for an unladen European swallow:
http://www.style.org/unladenswallow

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

 

[risingsun]

Date: 12/16/2007 2:59:39 PM
Author: denverappraiser

Date: 12/16/2007 1:02:40 PM
Author: risingsun
Dear Wink and Neil~forgive me for making light of your erudite explanations. It''s beginning to sound a bit like the calculations involved in determining the air velocity of a European versus an African swallow. I shall go quietly now...

Marian,

I''m not sure about grease-laden swallows, but this is the data for an unladen European swallow:
http://www.style.org/unladenswallow

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver

Neil...I think I love you

I am laughing so hard that I''m going into spasms

 

[Ellen]

Weirdos.

 

[Garry H (Cut Nut)]

I am surely sorry to take this back to the topic kiddies

About 1.5 years ago i did a little study with Drena''s earrings - I put a shallow stone in one and a tolkowsky in the other. After a week or so without cleaning the shallow was the clear winner. We tested several people in cafe''s and lunch places during the vegas trade fair and Paul from Antwerp, Wink I think, Peter Yantzer etc choose the shallow stone on in situ testing as being the better looking diamond.

I did some reporting here - cant find it, and it is a bit busy just now - if someone wants to try find it please?

 

[denverappraiser]

Date: 12/16/2007 6:41:17 PM
Author: Garry H (Cut Nut)
I am surely ...

Ah ha.

Neil Beaty
GG(GIA) ICGA(AGS) NAJA
Professional Appraisals in Denver