I publish here some photos and videos from a very interesting trip to an important area of gemstones and jewelry production in China – Panyu district of Guangzhou city, located in the South East China. Panyu has a long tradition of gem cutting and jewelry manufacturing, concentrating around 5000 factories dedicated to this industry nowadays.
In December of 2015 I was invited to this factory, to spend there a week and to give a short precision faceting course to one of their workers. They were very experienced in mass-production of standard commercially cut stones, using the technique shown on the photos below. However, they also wanted to learn the precision faceting technique, to be able to produce some unique high quality stones, with fantasy cuts based on special faceting designs.
I brought my faceting machine there and spent a really nice time at the factory. It was a very interesting experience, I had to teach every step of precision faceting with the help of one more person for translation to Chinese, but at the end of the week my student was able to produce his first high quality precision-cut stones!
Most of the gemstones available on the market are faceted at a cutting factories of this type, oriented to mass production. Faceting techniques and equipment for commercial cutting are very different to those used for precision faceting. The machines are much less precise, but, in contrast, they provide very high speed in cutting. Different operations, such as sawing, performing, dopping and faceting itself are done by different workers for large series of stones in a row, to reduce the time of each operation. Using this method, they are able to cut more than 120 stones in a day per each worker!
The photos and videos below illustrate the process used at that factory, step by step.
Sawing
Large pieces of rough stones are sawed before performing, to cut more than one stone from the same piece of rough. Trim saw with thin diamond blade is used for this.
Trim saw with thin diamond disk.
Preforming
Pieces of rough are manually preformed on a grinding wheel to give the stones their future shape.
More accurate performing for certain shapes can be done on a special machine. It uses a given shape patterns, like oval, marquise or others to produce stones of exactly same shape.
The table facets of the preformed stones are polished before the next step – dopping.
Grinding wheel for manual preforming.
Video: Machine for preforming to a given shape.
Dopping
This is the procedure to attach the preformed stone to a special metal stick called dop, for further faceting. A dopping wax is used for that, wax is molten with heat and the stone is heated too, to stick better to the wax. Once on the dop, the stone is centered manually, and also aligned using a special accessory to place the table exactly perpendicular to the dop axis.
Working place for dopping, with stones and wax located on a steel plate, heated from downside by spirit or gas lamp.
Video: Amazing precision and speed of work, for dopping of hundreds of gems in a very short time!
Stones on the dops, ready to cut!…
… And more stones ready to cut!… 🙂
Faceting
On this stage, facets of the stones are cut and polished, first all facets of the crown and later of the pavilion. The faceting is done on two laps, at first all the facets are cut on a coarser diamond lap, and after that all facets are polished on a tin lap with fine diamond polishing paste.
The dop with stone is placed in a special hand-held piece with octagon-shaped base on one side. This octagon base lies on the horizontal platform with a fixed height that defines the angle of the facet.
In other commercial faceting technique called “jamb-peg”, the angle is defined by the height of the hole supporting the end of the hand piece, while here the horizontal platform provides both angle and index position of the facet to cut. Of course, the depth of cutting is not limited in any way, contrary to precision faceting machines, so it must be controlled by the cutter.
Working place for faceting, with polishing lap, horizontal platform and several octagonal quadrants with stones ready for faceting.
Detailed view of the handpiece, with the switch mechanism for the rotation of the axis with regards to the main sides of the octagon base.
Horizontal platform for the handpiece, with possibility to quickly change its height using the supports on the secondary mast, fixed on the heights corresponding to desired angles for each type of facets.
This setup allows the cutter to go extremely fast on faceting. The changes of the index are done by rotation of the handpiece, done very quickly so it’s almost invisible in the following video. Once the tier of facets is done, he moves to the next tier simply changing the height of the platform, rotating the secondary mast. Finally, the stone is quickly checked with loupe and next handpiece is taken to cut next stone!
Video: Faceting process at amazing speed!
Finished stones are checked, graded, classified, weighted and stored, as shown on the photo below.
You can find more information about gem and jewelry industry in Panyu in an extensive article published in the Gems&Gemology journal.