Back to the beginning
 
     
 

 
 
 
 

Girdle Painting and Digging

Some content on this page are contributed by Good Old Gold, with thanks.

Introduction

When we talk about girdle painting and digging, we are primarily concerned with the light return from the upper girdle facets that are reflected off the lower girdle facets. Since girdle painting and digging affect the angles of these facets (and hence their light return), we need to pay special attention to them.

Upper Girdle Facets
Lower Girdle Facets

 

Identifying Girdle Painting and Digging

In this article, we will assume that you are familiar with the facet names of the diamond. However, do not be discouraged if you are not. Just keep the page on facet names open and refer to it frequently if you forget.

Before we can discuss girdle painting and digging, let us explain what it is, and how it is identified.

To begin, we need to measure 3 different parts around the girdle. This can be done using a number of measurement machines (such as the Sarin, OGI or Helium scanners).

  • Girdle Bezel: This is the girdle thickness at the part depicted in blue in the diagram below. This is where the crown mains (or bezels) and pavilion main facets meet at the girdle.

  • Girdle Half or Bone: This is the girdle thickness at the half facets (also called girdle bone) shown in red below.  This is where the half facets (upper and lower girdle facets) meet at the girdle.

  • Girdle Valley:This the girdle thickness in the valleys depicted by the green markers. Valleys are the thinnest part of the girdle and traditionally where girdle measurements and descriptions are given.

Definition

Analysing the measurements obtained above will tell us if the girdle is dug or painted. A brief description of each type of girdle is given below:

Classic Girdle:

The "ideal" classic girdle is cut to a nice evenness throughout from beginning to end around the diamond.
Girdle Digging

Girdle thickness at the halves (bone) are thinner and not consistent like the classic girdle. Conversely, you can say that the girdle bezels are thicker.
Girdle Painting

Girdle thickness at the girdle bezels are now thinner than the girdle thickness at the girdle halves (bone) disrupting the consistency of the girdle. Conversely, you can say that the bones are thicker.

 

Why is it done?

Diamond cutters paint or dig the diamonds' girdle for a number of reasons. Some do it to maintain extra weight on their finished product and thus increase its price, while others do it to achieve a certain optical characteristic.

For example, every Eightstar diamond is cut with painted girdles to achieve 'edge-to-edge brightness'.

Painting and digging, are quite common. Even 'super ideal cuts' (like Hearts and Arrows type diamonds) are no exception because every little increase in weight drives up the price of the diamond.

Why are we concerned?

We are concerned with painting and digging because as consumers, we do not want to pay for the extra weight.

More importantly, painting and digging affects the optical characteristics of a diamond. This is not surprising, since the each upper and lower girdle facet has one side attached to the girdle. Altering the consistency of the girdle thickness will affect the angles of these girdle facets and thus their corresponding light return.

So, not only do we pay for the extra weight if the diamond's girdle is dug or painted, we could possibly be getting a worse looking diamond.

In the next few pages, we will examine the optical effects of girdle painting and digging.

 
   

Next: Girdle Digging...