The bow tie effect shows up as a dark shadow across the center of your diamond. It looks like a bow tie. You'll see it most in oval, pear, and marquise cuts.
This isn't damage. It's not an inclusion. It's how light moves through the stone.
Light Reflection Problems Create Bow Ties
When light enters a diamond, it should bounce off the pavilion facets and come back to your eye. That's what creates sparkle.
The bow tie happens when facets don't reflect light properly. Light escapes through the bottom or sides instead of returning to you. This creates dark zones shaped like a bow tie.
The pavilion is the bottom half of the diamond. In elongated shapes, these facets are longer and positioned at different angles than round diamonds. If they're not aligned correctly, some facets block light instead of reflecting it.
Think of it as a shadow inside the diamond. The facets create blind spots where light can't reach your eye.
Cut Quality Matters Most
Poor cutting makes bow ties worse. Two factors control how severe the bow tie appears.
Depth percentage: Diamonds cut too shallow let light leak out the bottom. Diamonds cut too deep trap light inside. Both create shadowing. The ideal depth for oval diamonds sits between 58-62%.
Table percentage: This is the flat top of the diamond. Too large or too small affects how light enters and exits. For ovals, 53-63% works best.
A skilled cutter can predict bow ties before cutting. They adjust angles to minimize the effect. But
elongated shapes make this difficult. The long midsection creates challenges round diamonds don't have.
Facet Alignment Causes The Pattern
The bow tie's distinctive shape comes from how pavilion facets are arranged.
Oval diamonds can be cut with different facet patterns. Some use 4 main pavilion facets, others use 6 or 8. Each pattern distributes light differently.
When these facets don't align symmetrically, light reflects unevenly. The areas that don't reflect light form the dark bow tie pattern across the diamond's width.
Poor symmetry makes this worse. If one side of the diamond has different facet angles than the other, the bow tie becomes more obvious.
Diamond Shape Affects Bow Tie Severity
Round diamonds rarely have bow ties. Their symmetrical shape distributes light evenly in all directions.
Elongated shapes face different physics. The length creates more distance for light to travel. More surface area means more opportunity for misaligned facets.
Ovals, pears, and marquise cuts all share this elongated structure. That's why they're most affected.
The length-to-width ratio matters too. Longer, skinnier ovals (above 1.5:1 ratio) show more pronounced bow ties. Diamonds between 1.3:1 and 1.5:1 tend to minimize the effect.
Proportions Control Light Distribution
A diamond's proportions determine its light performance.
Too shallow: Light enters the crown, hits the pavilion at a low angle, and escapes out the bottom. This increases shadowing across the center.
Too deep: Light enters but gets trapped inside, bouncing between facets without returning to your eye. Creates dark zones.
Proper proportions: Light enters, reflects off the pavilion at the correct angle, and exits through the crown back to your eye. This maximizes brilliance and reduces bow tie visibility.
Cutters must balance these proportions with carat weight retention. Cutting for better light performance often means losing weight, which affects price per carat.
The Bow Tie Isn't Always Bad
Every oval diamond has some degree of bow tie. It's inherent to the shape.
A subtle bow tie can add depth and character. Some buyers prefer it. The contrast creates visual interest.
Problems start when the bow tie becomes severe. If it blacks out large portions of the diamond, it reduces brilliance and value.
The question isn't whether a bow tie exists. It's whether the bow tie dominates the diamond's appearance or stays subtle.
Why Grading Reports Don't Mention It
GIA and IGI reports don't grade bow tie effects. They note cut quality for round diamonds but don't assign cut grades to fancy shapes like ovals.
Reports will list symmetry and polish grades. Excellent grades in both help minimize bow ties. But they don't guarantee the absence of one.
This means you can't rely on paperwork alone. You must visually inspect the diamond yourself.
Body Position Affects What You See
Your position changes the bow tie's appearance.
If your body or head blocks the light source, you create additional shadows on the diamond. Move the diamond into direct light and the shadow lightens.
This is why diamonds look different in stores versus at home. Jewellery stores use overhead spotlighting that can exaggerate bow ties. Natural daylight often shows a more accurate picture.
The bow tie also changes based on viewing angle. Tilt the diamond and you'll see the shadow shift or disappear entirely at certain angles.
Light Leakage Creates the Shadow
Light leakage is the technical term for what causes bow ties.
In a well-cut diamond, light enters through the table and crown facets, reflects off the pavilion, and returns through the top. The entire path creates brilliance.
When facets are poorly aligned or proportions are wrong, light takes a different path. Instead of reflecting back, it exits through the pavilion or side. Those exit points appear dark because no light returns to your eye.
The bow tie pattern maps exactly where light is leaking from the diamond.
Multiple Factors Work Together
No single factor creates a bow tie. It's always a combination.
A diamond might have good depth but poor symmetry. Or excellent facet alignment but the wrong length-to-width ratio. These factors compound.
The best way to minimize bow ties is optimizing all factors together:
- Depth between 58-62%
- Table between 53-63%
- Excellent symmetry grade
- Length-to-width ratio between 1.3:1 and 1.5:1
- Skilled cutting that aligns pavilion facets correctly
Even with perfect numbers, some bow tie remains. That's physics. But proper cutting keeps it subtle rather than obvious.
It's not a flaw in the diamond's structure. It's an optical phenomenon caused by how the diamond was cut and how light interacts with its facets.
Understanding what causes it helps you evaluate whether a bow tie is acceptable or problematic. A subtle bow tie is normal. A severe one suggests poor cutting that compromises the diamond's brilliance.
Thanks for reading!
Jared & Brie