What is Diamond Brillianteering? Painting and Digging Out Diamonds

The final phase of diamond cutting is known as ‘Brillianteering”. That is when the cutter places the star facets, upper half facets, and lower half facets on the diamond. Collectively these facets are sometimes referred to as ‘ancillary’ or ‘minor’ facets. But there is nothing minor about the importance of these facets or their contribution to the light performance and overall beauty of the diamond! These 40 facets represent 70% of all the tiny mirrors that reflect and refract light in a round brilliant diamond, making a significant contribution to the visual appeal of the diamond.
Diamond Brillianteering
(Illustrations courtesy of GIA)
Therefore, the design and precision of the brillianteering has a significant impact on both the cut quality and the appearance of the diamond. Asymmetries in the meet points, in 3D alignment, or variances in facet angle and azimuth (pointing direction) will affect the ability of corresponding facets to work in optimal harmony, and can also result in demerits in the laboratory cut grade.
One of the most notable issues concerning the upper and lower girdle facets involves a technique used by the cutter to alter their angles and pointing directions. Known as ‘painting’ and ‘digging out’ these related techniques can be used for various purposes and can result in differences in weight retention, visual appearance, spread, and cut grade.
Gaining an understanding of the concepts of painting and digging from the literature is complicated by the fact that multiple terms are used to describe the same thing (see *note below). In this article we will try to more clearly define and illustrate the concept, and to help the reader understand the level at which these techniques begin to impact the diamond in material ways.
*Important notes about the lexicon. The following terms tend to be used interchangeably, sometimes leading to confusion.
  • Upper Half facets = Upper Girdle Facets = Upper Halves = Uppers
  • Lower Half Facets = Lower Girdle Facets= Lower Halves = Lowers
  • Bezel Facets = Crown Main Facets = Mains
  • Pavilion Main Facets = Mains
  • Azimuth = Radial Position = Pointing Direction
  • Shift = Tilt = Point (referring to facet direction)

Half Facets and the Standard Index

The cutting of a round brilliant diamond follows a very regular and symmetrical pattern around a 360° circle. There are eight main facets on both the crown and pavilion (main facets on crown are also called ‘bezel’ facets). In between each of these ‘mains’ are eight pairs of facets at the girdle known as ‘upper’ half facets and “lower” half facets, sometimes called the upper girdle and lower girdle facets. One of the best ways to visualize this is to view a Visual Proportion Analyzer (VPA) report from the AGS Laboratories, the foremost authority in cut quality analysis. The concept of ‘directional precision’ is important in understanding painting and digging.
VPA Diagram
Normally, the cutting instrument is set to the standard “index” where the eight main facets are pointing at regular intervals of 45°. The half facets comprise 22.5° each, with each facing or pointing to positions in 11.25° increments as the standard. Normally the half facets are each pointing in the direction of their midpoint (or 11.25°), but can be facing anywhere from +11.25° to -11.25° (or from 0 fully painted to 22.5° fully dug out) from that normal center direction. If the half facets point more toward the main facets, they are said to be “painted”, suggesting they are lightly placed. When the half facets are pointing away from the mains they are said to be “dug out”, suggesting they are cut down deeper.
VPA Diagram
Heavily Painted Upper Half Facets
(note the directional arrows pointing in towards the mains and the colored coded level of painting indicated in blue)
VPA Diagram
Lightly Dug Out Upper Half Facets
(note the directional arrow pointing slightly away from the mains on the pink shaded facets)
The examples above indicate intentional painting and digging by the cutter. It is important to note that it is most common to find diamonds that have some facets painted and some facets dug out in a seemingly random fashion. This is often simply an indication of lack of faceting precision resulting from inferior equipment or cutting skill, or lack of attention to detail. Wide variations can also be the result of attempts to use painting or digging to remove inclusions or correct other problems.

64 Bit Gear Cutting Machine

Another way to visualize the concept of indexing is through the lens of the cutting device itself which has a gear mechanism consisting of 64 positions around the circle. Each of the 16 half facets therefore consists of 4 ‘clicks”. The standard index is half way between each facet or 2 ‘clicks” of the device setting. If the cutter sets the device at 1 click (closer to the mains) he is painting, 3 clicks (away from the mains) and he is digging.
64 Bit Gear Cutting Machine
Normal Indexing
Illustrations courtesy of AGSL
Modified Indexing
Illustrations courtesy of AGSL
With normal indexing the girdle thickness is equal at the mains (bezel facets -green) and at the half facet junctions (red). If the cutter sets the index to 1, the half facets are shifted or tilted toward the mains (painting). If he sets it to 3, the half facets are shifted away from the mains (digging).
Painting
Painting
Digging
Digging
Indexing Chart
The consequence of the half facets pointing toward the mains (painting) is to decrease the angle between the halves and the mains thereby reducing the visual distinction between them. Pointing away from the mains decreases the distinction between the two half facets. Therefore both painting and digging have the effect of making different sets contiguous facets less distinct and more like a single facet. When severe enough, this can change the brightness and/or the scintillation patterns of the diamond. (see additional images below to help with this visualization).

Why do diamond cutters paint and dig?

There are five reasons that cutters may intentionally paint and/or dig out.
  • To retain carat weight
  • To increase ‘spread’
  • To adjust the girdle profile
  • To remove small inclusions
  • To remove light leakage

Retaining Carat Weight

Both painting and digging out can be used to retain weight. Because the market still rewards weight over beauty, if a diamond can finish out at or above a desirable carat weight, its value on the market can be significantly increased. In many cases a point or two (.01-.02ct) can make all the difference, especially in diamonds at ‘magic’ marks such as 1.00ct or 2.00ct. Non- standard indexing, especially painting on the much larger lower half facets, can easily retain the extra weight.
Digging out on either upper or lowers can be used to remove inclusions at the girdle line and improve clarity without having to recut the whole diamond, thereby retaining more weight.
This use of non-standard brillianteering benefits the manufacturer economically without adding value for the consumer. In fact, it can cost the customer more and in some cases the diamond may actually be diminished in quality in pursuit of that extra carat weight. A diamond cut specifically to retain more weight than necessary is sometimes referred to as a “swindled” or ‘cheated’ stone.

Increasing Spread

The dimensional ‘footprint’ of the diamond – its face-up visual size for a given carat weight – can be impacted by painting and digging. The article at the link in the "conclusion" section below gives a calculation of a diamond of 0.857ct that can range between 6.00mm and 6.21 mm depending on indexing.

Adjust Girdle profile

Painting and digging can also be used to level out the visual differences between the ‘hills and valley’, potentially resulting in a more favorable lab grade on the condition of the girdle. A wavy girdle can be evened out by strategic painting and/or digging. It can potentially influence the grader to render a better symmetry grade as well. Images below will illustrate how the girdle thickness is affected by different degrees of painting and digging on crown and pavilion.

Remove Inclusions

Digging out is sometimes used to remove inclusions and blemishes at or near the girdle line, thus potentially improving the clarity grade. Naturals and other features can be removed by altering individual half facets without having to recut all around, thereby saving weight and spread.

Remove Leakage

Painting on the crown can be used to remove some leakages present with standard indexing, thereby increasing the stone’s brightness. This technique is used on some ‘super ideal’ rounds to optimize the quantity of light returned to the eye. The Eightstar is an example of intentional crown painting for the purpose of making a diamond with ultimate brightness. This type of painting is not used to retain weight but rather for the purpose of optimizing light performance.

Differential Effects on Girdle Profile

When the half facets are pointed toward the mains the girdle thickens at the half facet junction. Pointing away from the mains has the effect of thickening the girdle at the point where it meets the bezel facet. The degree to which thickening occurs relates to the degree which the facets have been painted or dug out. It is therefore possible to get a sense of how facets have been brillianteered from examining the girdle line.
Normal vs Painted
Crown only Painting
Crown and Pavillion Digging

Effects on Visual Appearance

As the half facets are tilted toward the mains, the angle between the two half facets decreases thereby reducing the definition between them and making them look more like a single facet. Conversely, tilting the half facets away from the mains reduces the angle between the half facets and mains making them look more like a single facet. The following illustrations help in visualizing this effect.
Normal Indexing
Normal indexing. Notice good facet definition between bezel and half facets. (Illustrations courtesy of GIA)
Crown Painting
Painting (crown). Notice the decreased definition between the bezel facet and upper half facets making them appear more like a single facet. (Illustrations courtesy of GIA)
Crown Digging
Digging (crown). Notice the decreased facet definition between the two upper half facets, making them appear more like a single face. (Illustrations courtesy of GIA)
Pavilion Digging
Digging (pavilion). Notice the decreased facet definition between the lower half facets, making them look more like a single facet. (Illustrations courtesy of GIA)
Pavilion Painting
Painting (pavilion). Notice the decreased facet definition between the lower half facets and the pavilion main, making them look more like a single facet. (Illustrations courtesy of GIA)
Idealscope
AGS-104076846039
Idealscope
AGS-104075180035
ASET
AGS-104076846039
ASET
AGS-104075180035
Actual light performance images of two super ideal cut diamonds. The diamond on the left has crown painting that has eliminated virtually all light leakage (EightStar style), as seen most easily in the small white areas on the Ideal Scope of the diamond on the right. The painting has also resulted in the diamond drawing a bit more light from lower angles as seen in the increased amount of green in ASET.
Crown Painting
Brightness map (crown painting)
Standard Index
Brightness map (standard index)
Computer generated images courtesy of AGSL
The effects of painting and digging on the visual appearance of diamonds are largely dependent on degree to which it is present and whether it is done with consistency. It is often easier to see the effects of painting and digging in light performance images such as Ideal Scope and ASET, and in diagnostics such as VPA. If not extreme, the visual effects may not be apparent or may be so subtle that it would take a trained eye to discern.
While it is clear that crown painting can make a diamond brighter, it is less clear whether this has an overall positive impact on the appearance on the diamond. Scintillation patterns which are less well understood, are also affected in the process. Sacrifices in scintillation may be worth attaining extra brightness, but may be more in the realm of “taste” differences.

Simulated ASET maps

It is possible to simulate different types of painting and digging at difference degrees with use of software such as Octonus DiamCalc, in order to understand how light performance is impacted in different scenarios. These simulations assume perfect 3D symmetry, so the effects in these graphics are consistent across the entire stone as if cut with complete intention and precision.
The following are simulated ASETS with different degrees of painting and digging on crown only, pavilion only, and both crown and pavilion. Note that crown only painting has only minor impacts on the ASET signature (column 1A).
Visual Effects of Painting and Digging

Lab Cut Grading and non-standard Brillianteering

AGS Laboratories and the GIA approach the issue of non-standard brillianteering (painting and digging) in different ways. As we have seen, the purposes of non-standard indexing range from trying to retain extra weight to fine tuning brightness.
GIA, with its table-based grading system, punishes any non-standard brillianteering that reaches a certain point, regardless of the intent or effect. AGSL, because their cut grade system is light performance based and involves actual ray tracing of a 3D model of the diamond, does not punish brillianteering intended to improve the appearance of the diamond. Only if there are deficits in brightness, contrast, fire or leakage will the cut grade be lowered. The crown painted super ideal diamond in the example above (EightStar style) would be likely be downgraded by GIA from Excellent to Very Good because the GIA cut grading system is not sophisticated enough to distinguish actual effect of the painting or digging on light performance. GIA bases their strategy on the results of their observational surveys wherein most subjects reported that any significant levels of painting or digging resulted in diminished attractiveness.
Hiding weight to get to a magic carat weight, e.g. 1.50ct, certainly benefits the manufacturer by increasing the trade price. This comes at the expense of the consumer who pays extra and receives no benefit. This is the issue the GIA penalty is meant to address.
However, because the GIA cut grade system does not actually evaluate light performance it does not distinguish between brillianteering intended to "cheat" and brillianteering that may have been used to fine tune the stone and remove light leakage. So, in certain cases the GIA system punishes superbly crafted diamonds with top light performance.

Conclusion

Painting and digging out are variations of brillianteering, the final stage of the cutting process whereby the cutter adjusts the azimuth (pointing direction) of the upper and/or lower half facets. Either technique can be applied to the crown alone, to the pavilion alone, or to both the crown and the pavilion with various combinations and levels of severity.
The reasons why a cutter might use these techniques include retaining weight, increasing spread, removing inclusions or blemishes at the girdle line, and removing light leakage.
For an even more detailed look at how weight and spread are effected by indexing, please see this AGS article.
The degree to which painting and digging is present will determine whether and what kind of visual effects might result, and whether the laboratory cut grade will be effected.

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