A Guide To Bow Tie Effect In Diamonds (& How to Avoid it!)
What is the bow tie effect in Diamonds?
The bow tie effect is an optical phenomenon that is commonly found in elongated cuts such as the Pear, Oval and Marquise and is caused by the pavilion of the stone either being cut too deep or to incorrect proportions, resulting in a grey or black area across the stone when viewed table up.
That is the quick summary but let’s take a deeper look into this optical phenomenon and answer some of the common questions.
What Causes The Bow Tie Effect In Diamonds?
The bow tie effect is caused by how the pavilion (bottom) of the Diamond has been cut.
It should be noted that pretty much all Pear, Oval and Marquise cut Diamonds will have some degree of bow tie but it is much more obvious in some stones than others, this can be down to a number of reasons:
1) Deep Pavilions
One of the main reasons why it is more obvious in some stones is because they have a deeper pavilion, which affects the angles of the pavilion facets.
If the angle of the pavilion facets isn’t right, then the stone can’t achieve what is known as Total Internal Reflection (TIR), which is returning the maximum amount of light to the person looking at the stone.
The result of this is that light leaks out of the stone, which is the dark grey/black areas that you see.
2) Asymmetry
Whether a stone is symmetrical or not is another factor that can affect how obvious a bow tie is. The reason for this is that if the pavilion facets are not perfectly symmetrical, then it affects the angle of these facets, which affects how light interacts with the stone.
If the stone is asymmetrical, it can also affect the appearance of the bow tie, such as making it look more prominent on one side of the stone than the other.
3) Length to Width Ratio
Longer, thinner stones can have a more noticeable bow tie as once again, it affects how light interacts with the stone but this isn’t always the case as I have seen Diamonds that are long and thin that have a minimal bow tie.
How To Avoid Bow Tie In A Diamond
If you are looking for an elongated Diamond such as a Pear, Oval or Marquise, then you cannot completely avoid having a bow tie in your stone but you can find one where it only has a minimal impact on the beauty of the stone.
The best way to do this is to see the stone in person and look at it from multiple angles and in different lighting environments such as daylight, artificial light etc (just don’t run off with the stone!).
You won’t be able to tell if a stone has a bow tie or not just from looking at the Diamond report as they don’t provide any information relating to bow ties, the lack of proportion information on the report (they only state total depth for fancy cuts) also makes the report useless for checking.
Bow Tie Effect in Oval Cut Diamonds
Bow Tie Effect in Pear Cut Diamonds
Bow Tie Effect in Marquise Cut Diamonds
I'm Paul Haywood FGA DGA, the owner and founder of Haywoods Gems, I'm a fully qualified Gemmologist and Diamond Grader from the Gemmological Association of Great Britain.
