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Various ways of “treating” a diamond, such as heat, can be used to enhance the colorlessness of
a diamond or intensify the color of fancy colored diamonds. The results of these treatments can
produce temporary or permanent results. However, treated stones are worth far less per carat than
natural stones.
HPHT
High Pressure-High Temperature (HPHT) is a process that applies extreme pressure
—approximately 850,000 pounds per square inch — and very high temperature — of about
1,600 degrees centigrade — to the diamond. By altering the molecular structure of natural
diamonds, HPHT greatly enhances their color. Only certain types of diamonds can be affected
by this treatment, which can turn a brown diamond colorless.
Chemical Vapor Deposition
This square cut requires a higher depth percentage in order to maximize its brilliance. It has fewer
facets than the typical cuts. A princess cut diamond ring is very flattering to a hand with long fingers.
Laser Drilling
Lasers are used to minimize the appearance of flaws and make them less visible. The results of laser
drilling are permanent. Drilling does leave colorless cavities in the diamond.
Irradiation
The irradiation of diamonds can result in the production of fancy colored stones, especially blues,
greens and deep yellow. Radiation may also be used to reduce the flaws on a diamond.
Painting
This process involves painting a very thin coat of a chemical substance over the entire stone,
or part of it, to improve the color. Painting neutralizes the yellow in the stone and can improve
the color by as much as seven grades.
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