How the diamond was cut is vital to its overall sparkle and may also directly cause the bow tie effect. In this article, Benjamin Khordipour G.G. will explain the bow tie effect and whether you should buy a diamond with a bow tie.
- Diamond Shapes and the Bow Tie Effect
- Pros and Cons
- How to Tell if a Diamond has a Bow Tie Effect
- Talk to a Diamond Expert
What Is the Diamond Bow Tie Effect?
The bow tie effect is a visual display inside a diamond that wasn’t cut properly. The bow tie will appear as numerous dark facets that together form a “bow tie” shape. This effect is most common in oval, pear, heart, and marquise-shaped diamonds.
The bow-tie effect is caused by imperfect measurements of the diamond’s cut. When a diamond’s facets don’t reflect light correctly, dark “patches of unlit facets” appear in the middle of the stone.
This effect can be especially noticed as you move the diamond slowly from side to side.
Expert Note: The bow tie effect isn’t a result of light leakage, inclusion, or “chemical coloring” inside the diamond. The cause is simply an improper light reflection due to the cut. Essentially, the bow tie effect is a shadow inside a diamond.
Degrees of the Bow Tie Effect
The bow tie effect has many degrees, ranging from faint to intense. Depending on the cut quality, the bow tie can be very slight or so bad that a massive area is completely black, severely jeopardizing the diamond’s appearance.
The intensity of the bow tie effect changes depending on how you move it and what angle you’re looking at it. Additionally, if, while moving the diamond, your head or body blocks the interaction of light with the stone, you’ll likely interrupt the intensity of the bow tie effect.
When you move the diamond around, the shadow may also become lighter if the shadowed facet directly touches the light.
Important Note: Every brilliant-cut diamond (aside from perfectly round diamonds) has some tiny degree of bow tie, even the most expensive ones. The problem becomes when the bow tie effect becomes too intense and noticeable.
If you want to understand the boring mathematics behind the bow tie effect, skip to the end, where we get technical.
Diamond Shapes and the Bow Tie Effect
There are diamond shapes that are more easily impacted by the bow tie effect, and there are other shapes that rarely (if ever) have a visible bow tie effect. Brilliant cuts such as square, round, and cushion don’t feature this effect. These cuts have perfect proportions, and the facets distribute the light evenly.
| Bow Tie Effect | Faceting Style | |
|---|---|---|
| Round Brilliant Cut | No | Brilliant |
| Oval Cut | Possible | Brilliant |
| Cushion Cut | Possible | Brilliant |
| Emerald Cut | No | Step |
| Asscher Cut | No | Step |
| Marquise Cut | Possible | Brilliant |
| Pear Cut | Possible | Brilliant |
| Radiant Cut | Possible | Brilliant |
| Princess Cut | No | Brilliant |
| Heart Cut | Possible | Brilliant |
| Rose Cut | No | Rose |
The bow tie effect typically occurs in elongated cuts that follow the brilliant-cut faceting pattern. These cuts have long middle sections, and it is difficult to cut them without compromising the light reflection.
Pros and Cons of Diamond Bow Tie
The diamond bow tie effect is a consequence of an imperfect cut. But is it always a bad thing? Let’s review the pros and cons of this phenomenon.
Pros of the Bow Tie in Diamonds: Although generally considered a bad element, a diamond bow tie can have several positive aspects. The harsh bow tie in the diamond can give the diamond character, catch the eye more easily, and give it stronger flashes as the jewelry moves. Additionally, a bow tie can sometimes do a great job of hiding undesirable inclusions and imperfections. Finally, the bow tie can be a great way to leverage your negotiation with the jeweler when asking for a better price.
Cons of the Bow Tie in Diamonds: For many buyers, the bow tie diamond is a deal breaker when seen in a diamond. An intense bow tie is considered by many to be visually unattractive, disturbing, and a hindrance to the brilliance of the diamond. Additionally, if a consumer wants to sell a diamond with a bow tie, his price offers may be lower, and he will probably have a more challenging time finding a buyer. Finally, an intense bow tie indicates that the overall cutting wasn’t conducted on the highest order, which can mean additional problems lurk ahead.
Another factor to be aware of, and it’s neither a pro nor a con, is that the GIA Certificate does not mention if a diamond has a bow tie. It will mention the cut grading and symmetry but not directly mention how intense the bow tie is.
Of course, if you’re a mathematician (or have access to a diamond measurements calculator), you can calculate the strength of the bow tie using the size, ratio, and depth.
How to Tell if a Diamond has a Bow Tie Effect
Most diamond sales are now online, so you may think it has become more challenging to determine if your diamond has a bow tie effect. This couldn’t be further from the truth. There are many easy ways to know if your diamond has a bow tie.
Here are some of my top tips to use to discover if your diamond has a bow tie:
- Most websites show videos of diamonds (or diamond rings). Watch the center of the diamond carefully, and you should be able to tell easily if it has a bow tie.
- Ask the jeweler directly (or customer service). Anyone who picks up the diamond can see if it has a bow tie. If the company has a solid return policy, they will be very candid with you about whether a diamond has a bow tie or not.
- Check the GIA report or Appraisal to see the gradings for polish and symmetry. If you see they’re both “excellent,” you should have nothing to worry about. If you see they both have a “good” grade (or lower), investigate the bow tie.
- Ask for additional pictures and videos directly from a cellphone. Most jewelers will be happy to help. A cell phone video from a foot away from the diamond will easily indicate whether there is a bow tie.
The Mathematics Behind the Bow Tie Effect
The bow tie effect in a diamond is caused by the specific angles and proportions of the diamond’s facets. The facet positions will dictate how the light is reflected and refracted within the stone. The key mathematical principle involved is Snell’s Law, which describes how light bends through different objects.
A diamond has a high refractive index of approximately 2.42. Light entering the diamond will bend significantly. If the angles of the pavilion facets are not optimal, the light will not reflect correctly within the diamond, leading to light leakage and the creation of dark areas, known as the bow tie effect.
Another critical factor is the critical angle for total internal reflection, which is around 24.4 degrees for diamonds. When light hits a facet at an angle greater than the critical angle, it reflects internally rather than exiting the diamond. In an ideal diamond, the light will reflect multiple times within the diamond before exiting through the crown, maximizing its brilliance. However, if the pavilion angles are too steep or too shallow, the light will not reflect at the right angles, causing it to escape through the pavilion or girdle, resulting in the bow tie effect.
Mathematical modeling through ray tracing can predict the path of light within the diamond based on the facet angles and proportions. This modeling shows that slight deviations in the facet angles can lead to significant differences in light performance. In a diamond with optimal facet angles, light reflects efficiently within the diamond, avoiding the bow tie effect. In contrast, a diamond with suboptimal angles will experience light leakage, causing the characteristic dark areas. Thus, precise cutting and alignment of facets are crucial to minimizing the bow tie effect and ensuring maximum brilliance and sparkle.
Frequently Asked Questions
Is the Bow Tie Effect Bad?
Yes, generally speaking, the bow tie is considered a deficiency in a diamond. If the bow tie effect is very intense, it means that the diamond was not cut properly. A slight bow tie effect is sometimes considered desirable, giving the stone more personality and drama.
How to Fix a Bow Tie in a Diamond?
The only way to fix a bow tie is to repolish the problematic facets. If a diamond expert calculates better measurements for the diamond and cuts accordingly, this will correct the original poor diamond angles.
Will the GIA Certificate Mention a Bow Tie Effect?
No. The GIA doesn’t mention bow tie effects in their certificates. For that reason, we strongly recommend asking the jeweler directly if the diamond has a bow tie.
Which Diamond Cuts Have a Bow Tie?
Oval, cushion, marquise, pear, heart, and radiant cuts can all have bow ties inside the diamonds. Round diamonds, princess, emerald, square, and Asscher cuts cannot.
Does a Round Brilliant Cut Diamond Have a Bow Tie?
No. As mentioned above, a round diamond with perfectly equal facets will not have a bow tie.
Do Antique Diamonds Have a Bow Tie Effect?
Yes. Antique diamonds can have a bow tie, just like any modern diamond. In fact, because antique diamonds were cut by hand, imperfect cuts are expected. The bow tie in antique diamonds has a much smaller stigma attached to it than modern diamonds.
Do Lab-Grown Diamonds Have the Bow Tie Effect?
Like regular natural diamonds, lab-grown diamonds can have the bow tie effect. That being said, we strongly caution our readers to avoid lab-grown diamonds.
Talk to a Diamond Expert
If you have any questions regarding the diamond bow tie effect, we’ll be happy to answer them. Our experts have been in the industry for decades and can clarify all your diamond-related questions.
Feel free to schedule an appointment in our Showroom or reach us at 212-265-3868 for additional information.
