Bow Tie Effect in Cushions?

[gemnewbie]

Is the bow tie effect ever present in cushion diamonds?

I showed this picture of a GOG August Vintage cushion to a diamond expert, who though that this diamond might have the bow tie effect. I disagreed, since I thought the effect involved two triangles which are joined in the center of the stone. Any thoughts?

http://goodoldgold.com/diamond/6566/

 

[Lorelei]

Date: 11/21/2009 11:57:16 AM
Author:gemnewbie
Is the bow tie effect ever present in cushion diamonds?

I showed this picture of a GOG August Vintage cushion to a diamond expert, who though that this diamond might have the bow tie effect. I disagreed, since I thought the effect involved two triangles which are joined in the center of the stone. Any thoughts?

http://goodoldgold.com/diamond/6566/

That is a "maltese cross effect" showing in this diamond, not a bow tie. The cross effect can be seen more clearly in the ASET image. Any elongated fancy shape can show a bow tie but this cushion is more of a square shape and a bow tie isn't what is happening here.

 

[Hest88]

Right. The bow-tie effect is natural to some degree or another in elongated shapes, but it''s more of a dark shadow effect and is two-sided.

 

[gemnewbie]

Thank''s for the clarification.

To follow-up, is the Malteese Cross Effect an undesirable aspect of this stone? If so, can you quantify the level of undesireablility for me, in some way? I''ve read that a pronounced bow tie effect is a big negitive.

 

[gemnewbie]

Another question--I assume the Malteese Cross Effect is reflected in the ASET by the large blue areas in the outer faucets at 12, 3, 6 and 9 o''clock position?

As I recall, blue in a ASET is a reflection of shadow back from the obsrver, and isn''t necessarily bad as long as it''s evenly distributed and not overwhelming, right? What will this effect do to the light performance of the stone?

 

[kenny]

Be aware of the disadvantages of a still pic compared to real life or a video of a diamond.
Just because an area is dark in a still pic does not mean it will remain dark when the diamond is moved.

Think of those eight dark arrows in a pic of an ideal round diamond.
They do not remain black in real life when the diamond is moved around.
So it is with the shape called the maltese cross in GOG's chunky cushions.
It is just a prominent shape seen when the diamond is seen from the top.

Bow tie is an undesireable effect in which (when the diamond it rocked back and forth) a bow tie-shaped region remains predominately dark.
It is result of the cut and can be seen in some ovals, marquis and some cushions.

The maltese cross is just a name for the shape seen under the table of some cushions, particularly GOG's "New Antique" chunky cushions.
Go to Goodoldgold's website and watch some of their videos.
This is NOT a cut with problematic dark zones when the diamonds are in motion, like the bow tie effect.

 

[Hest88]

Gem, that Maltese cross windmill effect is the result of those wide, chunky facets in a cushion that tries to mimic the look you get in many OMCs. It''s strictly personal preference.

 

[stone-cold11]

Nothing wrong with it. It is the same as the arrows on a H&A stone.

 

[Michael_E]

Date: 11/21/2009 11:57:16 AM
Author:gemnewbie
Is the bow tie effect ever present in cushion diamonds?

The "bow tie" in any stone is a reflection of your head and upper body, also referred to as head shadow or obstruction and is often confused with "extinction" in colored gems. The dark areas occur in all stones in a number which is equal to twice the symmetry of the stone. By example all stones which are symmetrical about one axis, such as pears and ovals, will show two dark areas which look like a bow-tie. Stones with two axes of symmetry such as cushions and other squarish shapes will show four dark areas. Stones, such as rounds with four axes of symmetry will show eight dark areas which are called "arrows" by some folks. This effect will show in nearly every stone which you look at...if you get close enough. For better cut stones the object is to have this effect show only after you get closer than you normally would in daily viewing. Get three feet away and there are almost no stones which show "bow-tie" since your head and upper body are so far away.

Want to experiment ? Grab any stone that you''ve got handy, put it directly in front of you, close one eye and move it closer and farther away. You''ll notice how the dark areas of your reflection get larger as you get closer, smaller as you get farther away and disappear altogether when you get far enough away. When buying a stone that shows a distinct bow-tie in vendor pictures, I would suggest asking the vendor to take pictures at varying distances or just ask them at what distances the bow-tie becomes apparent. Remember that most pictures are taken pretty close to the camera and so most stones having one or two axes of symmetry will show a bow-tie in the picture and may not IRL.

 

[CharmyPoo]

It is all personal preference but many on PS actually prefer the Maltese Cross.

 

[Karl_K]

You really need to watch videos to see how chunky faceted diamonds perform.
The ASET and even regular pictures do not show you.

 

[Rhino]

Regarding the bowtie you''ve received sound councel from everyone here. Is it ever present in cushions? Absolutely. In fact there are many vintage faceted cushions that have it as cutting them to the delicate balance in angle relationships it requires is not an easy task.

When the crown and pavilion angle relationship is such that the crown angles are drawing in too much reflection of the observer (generally blues in ASET) and the pavilion is effectively reflecting back that darkness to the eye this is what causes the bowtie. In my most recent consumer''s guide to cushions video I do in fact use a perfect example of this which you can see rather plainly in our indoor diffused lighting and in our bonus footage of the same diamond which is taken in natural daylight. In the clips I purposely put ASET and Diamxray photography to show the visual correllation. I also use one of these alongside of it to demonstrate the maltese cross directly next to it. The optics are entirely different.

Regards,

 

[ChunkyCushionLover]

Date: 11/21/2009 4:16:40 PM
Author: kenny
Be aware of the disadvantages of a still pic compared to real life or a video of a diamond.
Just because an area is dark in a still pic does not mean it will remain dark when the diamond is moved.

Think of those eight dark arrows in a pic of an ideal round diamond.
They do not remain black in real life when the diamond is moved around.
So it is with the shape called the maltese cross in GOG''s chunky cushions.
It is just a prominent shape seen when the diamond is seen from the top.

Bow tie is an undesireable effect in which (when the diamond it rocked back and forth) a bow tie-shaped region remains predominately dark.
It is result of the cut and can be seen in some ovals, marquis and some cushions.

The maltese cross is just a name for the shape seen under the table of some cushions, particularly GOG''s ''New Antique'' chunky cushions.
Go to Goodoldgold''s website and watch some of their videos.
This is NOT a cut with problematic dark zones when the diamonds are in motion, like the bow tie effect.

Good post Kenny.

I would ditto this, the GOG August Vintages are designed to have a big bright maltese cross, the exact opposite of a dark bowtie or a dark maltese cross. Jon at GOG has spent considerable time designing a line with standards that dictate that if all 4 sides of the maltese cross aren''t strongly reflecting light (red in the ASET) than the stone does not qualify for his August Vintage Line.

Most non optimized cushions (non August Vintage Antique Chunky Cushions) especially the more rectangular ones contain a bowtie or at least two of the mains in the cross show leakage(ASET white or black), partial obstruction(ASET blue) or only reflect indirect light back to the viewer(ASET green). You can view this from a photograph but it is best seen by the observation of white, black, blue or green being seen in all or part of the 3,6,9,12 o''clock pavillion main facets (the ones under the table that make up the cross) being seen as a color other than red in the ASET image.

 

[gemnewbie]

Thanks to all who replied. Thought I understood, until I read Chunky Cushion Lover''s post. In the ASET of the GOG diamond, there''s large blue areas at the 12, 3, 6 and 9 O''clock posiitons on the table. In your post, Chunky Cushion Lover says this is bad. Now I''m confused???

 

[ChunkyCushionLover]

Date: 11/22/2009 10:15:10 PM
Author: gemnewbie
Thanks to all who replied. Thought I understood, until I read Chunky Cushion Lover''s post. In the ASET of the GOG diamond, there''s large blue areas at the 12, 3, 6 and 9 O''clock posiitons on the table. In your post, Chunky Cushion Lover says this is bad. Now I''m confused???

Gemnewbie,

This diamond is an August vintage with fantastic optics. All 4 leaves under the table(the small square in the middle) making up the cross are red indicating excellent light return in the ASET).

What you are seeing is blue in the ASET in the outer crown facets (the blue parts on the outside). The reason why Karl K has stated you can''t judge well enough from a stationary picture or ASET image is that sometimes the blue areas are areas of contrast and can be switched "on" and show fire and contrast. This would be observed if a slight tilt causes the blue to turn to red in the ASET. This is quite common in the outside crown facets and is not something you would have to worry about unlike if you saw large blue areas under the table.

I would request a video comparison of this stone with others in the August Vintage line, you will likely find they are very similar and this one as well as the others have some of the best optics of any chunky faceted cushion you can find in the marketplace.

I wouldn''t worry about the obstruction at all(blue in the ASET), and if in doubt ask Jon at GOG he will certainly give you an honest answer and back it up with a video upon your request.

Regards,
CCL