HCA Really Works!

[bookworm21]

I bought a pair of earrings through WF a week ago, but ran the numbers through the HCA after my purchase. One stone rated Excellent across the chart. The other rated as "Worth the buy if you can get a good buy" or something along those lines.

I''ve looked at the two stones in every light possible, and I just wanted to share that the naked eyes (mine, anyway!) can definitely discern the difference in terms of light return and sparkle. The AGS Ideal, HCA excellent returns light from every single angle and is absolutely breathtaking. The GIA, HCA Good also sparkles a lot, but it doesn''t return as many sparkles as the AGS stone although it is still a gorgeous stone.

Just thought I''d share with those who are wondering whether there really is a discernable difference in light return based on HCA scores.

 

[pricescope]

Cinderella, could you please post the numbers (proportions) for these stones?

 

[bookworm21]

Sure. Here''s the GIA Sarin:
Total Depth: 60.9%
Pavilion Depth: 43.3%
Pavilion angle: 41.0
Crown Height: 15.5%
Crown Angle: 35.1
Table Size: 56.2%
Culet: Very Small
Girdle: Thin-Medium

AGS:
Total Depth: 61%
Pavilion Depth: 43.2%
Pavilion Angle: 40.9
Crown Height: 15.4%
Crown Angle: 34.8
Table Size: 55.6%
Culet: Pointed
Girdle: Very Thin-Medium

The HCA number difference is very slight: 1.7 vs. 2.1, but it is enough for me to notice with the eye when the two stones are compared side by side. I''ll definitely be using this tool for any future purchases.

 

[pricescope]

Date: 4/5/2006 5:51:48 PM
Author: Cinderella

The HCA number difference is very slight: 1.7 vs. 2.1, but it is enough for me to notice with the eye when the two stones are compared side by side. I''ll definitely be using this tool for any future purchases.

It''s amazing that you are able to discern the difference. Maybe one of the stones has painted girdle (to avoid light leakage at the edges)?

 

[bookworm21]

I don''t know about the painted girdles. But I did think that it was all in my mind too. So I tested myself by switching them around and not looking at them under a loupe. Then I held them in different lighting sources and was able to pick out the one with the better HCA score each time, based on the flashes of light and such (not quite sure how to describe it: intensity of sparkle, perhaps?).

When I upgrade, I do plan on using the HCA to guide my purchase to avoid this, because it''s simply driving me nuts. The earrings match in color and everything, but the slight difference in sparkle annoys me. Crazy, but true.

 

[pricescope]

when you did your research, have you seen Ideal-Scope images?

 

[bookworm21]

Yes, and the IS looked great for both stones to me, but I am by no means an expert. Let me see if I can manage to post them here.

 

[bookworm21]

And here''s the AGS stone that scored better on the HCA (don''t know how to attach multiple pics to one post).

 

[pricescope]

Thanks for posting the images, Cinderella. They obviously look very similar...

 

[strmrdr]

strange the numbers are very close and both IS images look good.
Wierd....

 

[MissGotRocks]

No huge glaring differences - go figure!

Are you going to keep the earrings?

 

[bookworm21]

Strm, I thought it was weird too that I could make out the difference. But goes to show some people are color sensitive, some are clarity. Guess I''m sparkle sensitive, if there is such a thing.

MissGotRocks, yes, I''m keeping them until I get to upgrade them. I had to wheedle my bf into buying me these (and it''s not as bad as it sounds, I swear! We live together and have together for over 10 years, so it''s like we''re married, we just haven''t made it official yet). I''m planning to upgrade them in about a year or so, and I''ll really be using the HCA as one of the primary tools.

 

[pricescope]

It looks like AGS graded stone (second picture) has thicker pavilion mains. Also there is some difference in the girdle profile...

 

[Garry H (Cut Nut)]

Date: 4/5/2006 7:02:00 PM
Author: Cinderella
Strm, I thought it was weird too that I could make out the difference. But goes to show some people are color sensitive, some are clarity. Guess I''m sparkle sensitive, if there is such a thing.

MissGotRocks, yes, I''m keeping them until I get to upgrade them. I had to wheedle my bf into buying me these (and it''s not as bad as it sounds, I swear! We live together and have together for over 10 years, so it''s like we''re married, we just haven''t made it official yet). I''m planning to upgrade them in about a year or so, and I''ll really be using the HCA as one of the primary tools.

Cindy you are giving me credit that is not earned

The first stone ideal-scope image is slightly painted - and that helps the ideal-scope image not show as much leakage.
The painting make the stone a bit like ACA new line or 8* diamonds and they have a look that some people like and others seem not to.
That is probably causing more difference than the slight proportion diference which is mitigated by the painting anyway.

Do a search on painting or look in the FAQ section to learn more about this if you wish

 

[bookworm21]

Hm...thanks Garry, I will look into the painted girdles, especially since they have such an effect on the visuals of a diamond.

 

[argh&stuff]

Okay, I''m not getting it. And the FAQs not helping.... what does painting a girdle do? And if I buy from WF, how do I know if they painted the girdle? Is painting "bad?"

 

[bookworm21]

I just read John Quixote''s explanation about painted girdles and I''m a bit confused too. So painting a girdle is not to improve the visual performance of a diamond? Rather, it''s just to retain as much weight as possible without compromising the integrity of the visual effects? Also, if I don''t like the way the above GIA diamond performed, does that mean my preference would lean towards the Classic ACA versus the New Line?

 

[pricescope]

Date: 4/5/2006 8:02:02 PM
Author: argh&stuff
Okay, I'm not getting it. And the FAQs not helping.... what does painting a girdle do? And if I buy from WF, how do I know if they painted the girdle? Is painting 'bad?'

see Girdle Treatments: Cheated Girdles, Tweaked Girdles, Digging & Painting

More links:

• Painting and Digging: Painted Girdle by GoodOldGold
• Girdle Treatments: Digging, Painting, Cheated and Tweaked - by Whiteflash
• PAINTING AND DIGGING OUT by GIA

 

[JohnQuixote]

The differences being noted in these 0.4 ct diamonds could be caused by the panoramas of illumination, the lower girdle facets (what is what I suspect is the major player here), grease on the pavilion of one of the diamonds, etc. I will see if I can pull the scans on those 2 stones tomorrow.

Brillianteering (painting and digging) is a fun topic on PS these days.

Here is a post reprinted from this thread.

Date: 3/13/2006 1:56:29 PM
Author: oldminer

It sure sounds as if either painting or digging can be useful in getting a sought after overall end result. These are expert terms that are nothing new, but people seem to feel a little frightened when they hear the terminology. Nearly every diamond has a decision maing process behind its cutting. The end result is what the consumer gets to appreciate. When done properly, there is no problem with an appropriate amount of painting or digging. When the diamond is finished, it speaks for itself.

I'm seeing this as well.

These approaches have been around for generations. Digging and painting are just words. They are parts of the manufacturing process, like cleaving, sawing, blocking, etc. They are not common parlance when discussing diamonds in the mainstream: If you drop these terms there are many jewelers and appraisers who won’t even know what you’re talking about. They are nothing to fear. Poor brillianteering will result in an inconsistent, wavy or knife-edge girdle, which will be downgraded by reputable labs.

A lot of buzz (and worry) has been created on the forum lately. Here is a simple overview.

With the vast majority of diamonds:

The thickness of the girdle is marked at blocking, and revisited before brillianteering. As the polisher puts the facets on he meets those marks. He may dig a bit or he may paint, depending on the desired yield and girdle thickness. It is all very natural. The approach is like choosing a fork or a spoon, according to the dessert you’re eating. The intent is to finish the diamond beautifully, particularly in premium makes (often seen on PS) where utmost care is taken throughout the process.

In extreme cases:

The main reason for extreme digging is because a stone may be steep/deep and there is a need to make that stone appear to have a medium or thin girdle. Remember, the desired girdle thickness is marked. By digging the upper and lower halves, starting from the girdle out toward the poles, thinning of the girdle occurs and the cutter meets the mark. This tends to hide weight. Digging may also be referred to as gouging.

In the case of shallow diamonds (where the girdle is marked to be quite thin), the cutter may need to start from the poles and polish toward the girdle to preserve the marks and avoid thinning the girdle any more. This is painting. If too much material is taken away it could result in a knife-edge girdle.

Of the two, digging is far more deleterious than painting. It can hide weight and reduce performance.

The ‘buzz’ lately is because GIA has decided to downgrade a certain level of digging or painting without analyzing the actual diamond. This is positive for average consumers in common situations (like the mall) as they will be protected from gouging for the purpose of saving weight… Unfortunately, a small baby was thrown out with their bath water: A few brands of the most carefully finished premium diamonds are painted on purpose. Coupled with optical symmetry, this technique can result in some of the most spectacular diamonds in the world. Unfortunately, along with such shortcuts as rounding of numbers, GIA is lumping that tiny percentage of wonderful premium makes in with the larger percentage of ‘save the weight’ cases.

With premium optical symmetry, like we often see on Pricescope, beauty was always the objective. It was not about saving weight. If the girdle is consistent and the painting was deliberately designed to beautify (as with Lynn’s diamond) it should not be downgraded.

Hope this helps.

 

[argh&stuff]

Is this related in any way to the thin white, chalky line that is sometimes seen around the girdle of a diamond? I saw that on a diamond at a local store, and it made it look like it''d been "popped" out of a plastic sheet, like tokens you pop off a sheet for board game. Looked cheap to me.

John, I''m planning on buying from WF (been working with Jamie); do your diamonds tend to have this chalky line?

 

[JohnQuixote]

Date: 4/5/2006 8:44:40 PM
Author: argh&stuff
Is this related in any way to the thin white, chalky line that is sometimes seen around the girdle of a diamond? I saw that on a diamond at a local store, and it made it look like it'd been 'popped' out of a plastic sheet, like tokens you pop off a sheet for board game. Looked cheap to me.

John, I'm planning on buying from WF (been working with Jamie); do your diamonds tend to have this chalky line?

argh&stuff (that is my fav screen name in a long time)

It sounds like you're seeing bruted or unfinished girdles. This has nothing to do with painting or digging. In these cases the diamond's girdle was left unfaceted - often seen in mass manufacturing situations with weight retention as a priority, or where the cutter believed polishing the girdle might cause color to be reflected back inside. More information in this thread.

I hope you're having fun with Jamie (we do). I trust she's treating you right.

Look, guys and gals. Painted does not mean bad. There are people who are trying to 'paint' painted as bad. It's not so - and it is not the largest visible difference in these diamonds:

I pulled the manufacturer's reports and the largest difference is the length of the lower girdle facets. The GIA has 80% while the AGS has 75%. This alone will cause subtle differences in the character of the performance.

 

[strmrdr]

Thanks John that explains it:
The GIA has 80% while the AGS has 75%.

It didnt look like that big a difference in the IS but didnt look at them side by side and its enough to make far more difference than the painting.


For the record my position on painting is that its different some like it some dont.
Is it bad? depends on if you like it or not :}

 

[argh&stuff]

Thanks John.

I think I get what you''re saying. All I know is that Brian looked over both the diamonds I''m considering, and he says they both rock.

Jamie is really good at explaining things to me, and she''s patient with my indecision, which is a blessing. She''s also worked a LOT with my girl (who wasn''t even supposed to be involved!!), and I think she''s even been able to calm her down some from calling and emailing all the time.

Just seeing the level of knowledge you have, and linking that to WF gives me peace about the whole buying online thing. Thanks for that; I''ve had anxiety.

So, your diamonds aren''t unfinished on the girdles? Sweet. I didn''t like the popped-out-of-plastic look.

 

[bookworm21]

John, thanks for your reply and for going to the trouble to pull up those reports. Both the stones are beautiful, don''t think that I don''t like them, I love them, it''s just that when I can notice ANY kind of difference, it drives me up the wall. It''s like an OCD.

Argh&stuff, I worked with Jamie too for the purchase of my earrings, and she was very patient with my impatient questions.

Please explain why the lower girdle facets would cause a difference in the visuals of the diamonds. I''m sorry, I''ve read a lot on here, but there''s still so much that escapes my knowledge.

And John, does this mean that I prefer the look of a classic ACA vs the new line ACA? (For future reference.)

Thanks.

 

[JohnQuixote]

argh&stuff,

Trust and security must accompany the decision to purchase online. I'm grateful my elaborations here have helped with your (natural) anxiety. Keep discussing things with Jaime - you won't be disappointed - and my extension is always available to you as well.

Cinderella,

From one OCD-er to another,

you are welcome. As Brian would say 'there is always a nose between the ears,' meaning that earrings can be slightly different and maintain their appeal. As a matter of fact, we have clients who purchase, on purpose, a new line ACA and a classic ACA as earrings - just to have one of each.

The lower girdle facet lengths determine how thick the pavilion mains will be. Remember, the mains are the engines that drive light return. Your AGS diamond has shorter LGF, thus thicker pavilion mains: With optimum major configurations this results in robust light return in low light conditions. Your GIA diamond has long LGFs and so, narrower mains, which will result in more active return in direct light conditions. The distinctions are very fine, but are notable (especially to OCD-ers). Some diamonds are cut specifically with thick mains to perform best in low light conditions, like candlelight - others are cut with narrow mains to perform best in bright, direct light conditions. Diamonds can also be cut for a balance. Please know (as I imagine you do) that these are like subtle differences in fine wines (a 2002 Far Niente Cabernet is slightly more mellow than its 2003 companion). To non-wine enthusiasts these are not notable at all, but conneseuers make such distinctions.

 

[JohnQuixote]

Date: 4/5/2006 9:27:19 PM
Author: strmrdr

Thanks John that explains it:
The GIA has 80% while the AGS has 75%.

It didnt look like that big a difference in the IS but didnt look at them side by side and its enough to make far more difference than the painting.

For the record my position on painting is that its different some like it some dont.
Is it bad? depends on if you like it or not :}

Just so. I suspected the LGF were different but had to see the manufacturer's reports to confirm 5% difference.

 

[strmrdr]

Cinderella,
my 2c for future reference, go classic and ask about the lgf% staying in the 78%-80% range.
I think you would be happier with that combination.

 

[bookworm21]

John, thanks again for clarifying. I understand now. And yes, I agree with Brian''s "there''s a nose between the ears," which is why I decided to keep the earrings. That, and also knowing that most people wouldn''t notice the difference anyway.

Strm, thanks for the reference. I''m saving that info for my engagement ring to make sure I get the numbers that I''ll be happy with.

 

[Garry H (Cut Nut)]

i think you are all wrong

Earrings should have hCA scores under 2 and be rather shallow.

 

[Rhino]

I''d concur with Garry''s statement. You''re not the first person to note these differences Cinderella. Through observation testing the greater majority of consumers concur your observation as well. If you''ve read our article on the subject it is an experiment we''ve conducted over the course of the past 5-6 years. Congrats on your earrings.

Kind regards,