Avalon Plus

Home Grading & Branding Avalon Plus

The "smoothness" of a facet is the degree in which polishing lines are visible. It is therefore an important aspect of the finish grade of a diamond’s facet. Because of the constantly increasing quality demands placed on polished diamond, smoothness becomes increasingly an important diamond quality feature .

Detection methods

The loupe

Many polishers evaluate ‘smoothness’ with a loupe (magnification 10x). The facet is observed under a small angle. The difficulty of this method lies in the positioning of the stone in relation to a light source, in order to put the facet in reflection (known as ‘scheerlicht’). Varying the light intensity by tilting the stone makes the polishing lines visible.

The microscope

The evaluation of ‘smoothness’ with a microscope is done in the same way as with the loupe, or through the stone. However, by using a microscope, one has better control of lighting conditions and stone manipulations. The availability of higher magnification is an additional improvement.


By using a special light source, Avalon visualises the surface finish of a facet with very high contrast. This requires the facet to be positioned perpendicularly to the optical axis of the measuring tool, which can easily be achieved when the stone is still in the tang. This brings us to the essence of the device. ‘Smoothness’ can be observed by the polisher (during the polishing process and without having to remove the stone from the tang) and allows him to intervene immediately when necessary. The polisher will be able to visualise smoothness without any difficulty, whereas a later examination of the stone can only be completed with traditional and less user-friendly tools.

The result is an increased efficiency.

To minimise the polisher’s subjectivity when assessing a diamond’s smoothness, WTOCD developed an upgrade of the Avalon: the Avalon plus or Avalon+.

This upgrade allows facet’s smoothness to be objectively measured and colour graded according to the HRD Antwerp standards for polish grade.

Polishing lines

The picture shows an image of polishing lines on a pavilion half. Heavy polishing lines are clearly visible as a pattern of white stripes under oblique light. The polish grade will depend on the visibility of the polishing lines.

Extra facets

The picture also shows extra facets. These appear by accident or to mask remainders of the rough diamond. In both cases, they lead to a downgrade of the polish grade.


Burn marks look like faint oil stains on the facet. These marks can be more obvious when looking at the defect through the diamond from the opposite side. The cause of burn marks is oxidation of the surface due to overheating the diamond during the polishing process.

Fine Scratches

Fine scratches can lead to a downgrade of the polish grade. This depends on the visibility. According to the internationally recognized grading rules, diamond grading has to be performed when viewing the diamond from the crown side with a loupe 10x. Graders often tend to look at scratches on the table, through the pavilion side. This can lead to discussions between grading labs and polishers about the correct polish grade. Very fine ‘naat’ lines and structure failures on the facet surface are also visible and can lead to the same discussions.

Facet geometry
This instrument can also perform facet measurements, using different icons on the right side of the pc-screen. Unlike other measuring tools, the Avalon+ uses a plane through the girdle as reference for its measurements. This implies that the girdle has to be perfectly round and parallel to the table.


Related Products