As you already know, before having a perfect finished product in your hands, the gem rough must go through various steps. Everything starts with a sorting process. Rough stones are sorted mainly according to their inclusions. Thai cutters inspect the stones to make sure there are no fractures inside that will cause problems during the cutting phase.
The first preform is used to establish a simple desired shape for the cut. This helps the faceter to look more closely at the stone and to orient it correctly. The entire process is performed with bare hands. This method is achieved by grinding the stone on a spinning wheel to remove the debris and to get only the basic desired form of the cut. Water is used to prevent overheating.
The sorting process is used to determine the size and condition of the stones. They are divided into different lots that will be used differently depending on the needs of the clients.
What Is Doping?
Doping the stone to a wooden or metal dop stick means attaching the stone to the stick, usually with adhesive wax, epoxy, or cyanoacrylate glue. Doping allows the gemcutter leverage over the whole cutting process, but also the safety of his fingers from the spinning wheel.
The first step is to heat all the components: the wax, the dop stick and the stone. Then the cutter applies the wax to the dop stick, immediately brings the stone and the dop stick together and lets them cool off. It is important to note that they keep rotating the stone while heating it up to prevent too much heat from a certain angle and then produce cracks from the inside.
Gem cutters must remove the stone from the wooden stick depending on which side of the stone would be cut so that they can turn it and dop it again at a different angle.
JAMB PEG MACHINE
The Thai Jamb Peg Machine
The machine works by attaching your stone to a wooden dop stick and then sliding it on a plastic wheel that gives you their index.
In case you don't know, an index is a gear that controls the rotation of your gem. They are usually available in a variety of sizes, but 64 and 96 are the most common. On the Jamb Peg Machine, the index plastic wheel comes in a variety of indexes but 8 is the most common.
Cutters then stick the end of their top pin to the desired hole in the Jamb Peg Head, which creates the correct angle. For a shallower angle, they use a lower hole and for a steeper angle, they use a higher hole. The plastic wheel then sits against a metal plate working as an anchor to rotate against it for quick index cutting. The head can be adjusted with knobs at the top aside in order to micro-adjust the angle in the index. In this way, you can cut the exact facet easily and repeatedly.
Only professional gem cutters may use these machines because there is no sign of how to stop the machine when the facet is complete. Understanding how these machines works takes years of experience and many failures. We invite you to watch our YouTube video at the end of this article for more information on this machine.
Thai Gemcutters: Best Cutters In The World? (With Justin K Prim)
(Full YouTube Video at the bottom of this article)
Justin K Prim, an expert lapidary historian, was asked several questions about Thai gem cutters and Thailand's global reputation as the world's gemstone capital.
The method is a bit different since it is done completely by the eye. So how does it work? The dopstick is inserted in a handpiece that allows precise control of positioning but doesn't have any fixed angles. Flat facets are cut over the entire surface of the stone, usually in a highly symmetrical pattern.
Before processing to the cutting phase, gemcutters prepare the machine by adding diamond powder mixed with coconut oil and spread the mixture with a piece of cotton. The polish grind part is made of copper, which interacts very well with corundum. They gently place the stone onto the lap and brush it back and forth across the surface.
Cutters apply enough pressure to hold the stone in touch with the cutting surface until they have cut it all the way to the depth setting. When the first facet is cut, they turn the gem over to the opposite index setting and repeat the cutting process until the facet is fully cut to the chosen depth. Two wheels are used simultaneously. One for cutting, one for polishing. And the cutter moves from one wheel to the other so there's no need to change laps.
The coconut oil and diamond powder seen in photos 1 and 2 are used to reduce friction on the copper wheel.
How Do Gemcutters Cut The Different Facets?
The table of the stone is cut freehand. The cutters connect a 45-degree connector to a 90-degree faceting unit of the lap.
Keeping the adapter, they have to incline their hand at 45 degrees, so that the overall angle is 90 degrees. The crown and pavilion are essentially cut to form a lens and reflector. These two elements concentrate and guide the light, then reflect it back to the eye.
The facets of the crown become the reflector, bouncing light across the interior of the stone, and then back upward and outward to the eye. In this process, the edges of each facet are not connected to each other perfectly. They will be aimed at the crown polishing process.
All of these steps are performed with the naked eye, which contributes to the impressive work and patience from gemcutters. The cutting process necessitates years of practice and complete focus on each task.
Last Step: Polishing
It's the final step. A special polishing lap will be used, which is much finer than the faceting lap.
Each facet is then individually polished to a high glow, giving a fine lustre to the stone. Polish the table facet by adding a stone to a sticky dop, with a dop 45 adapter along with a copper spinning wheel with a 50K Diamond powder strength.
This process is used for polishing the main crown facets as well. Each gemstone table needs a different spinning wheel lap for polishing. The girdles will be the last part to polish and the techniques for preparing the laps vary with the materials used.
Most Thai machines have two wheels of different material (see the brownish and greyish "disks") that are used for faceting and polishing at the same time.
Since different stones are frequently inconsistent in their ease of polishing, particularly faceted stones, gemcutters are generally very creative in trying new combinations of polishing agents and polishing surfaces.
Our Thai Factory
Are Thai Gemcutters The Best Cutters In The World? Find Out In Our Interview With Justin K Prim, Lapidary Expert:
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Social Media Manager at GemMatrix
With over ten years of marketing experience, I finally decided to settle down in Bangkok to work in an area that I have always been interested in: the gemstones industry. I'm still learning how the market works on a daily basis, and I enjoy sharing my experience with those who are interested in learning more about gems in general.